WO2008151371A1

WO2008151371A1 - Crop meter and uses therefor

Info

Publication number: WO2008151371A1
Application number: PCT/AU2008/000842
Authority: WO
Inventors: Ivor Malcolm Awty
Original assignee: Agriculture Victoria Services Pty Limited
Priority date: 2007-06-12
Filing date: 2008-06-12
Publication date: 2008-12-18
Also published as: AU2008261611A1; NZ582119A; AU2008261611B2

Abstract

The present invention provides an improved vehicle-mounted sonar device for determining one or more plant yield characteristics, wherein the device comprises an ultrasonic transmitter for transmitting timed pulses of ultrasonic energy towards plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants, an ultrasonic receive for receiving echoes from the plant material, means for filtering the received echoes, a temperature sensor and computational means for correcting for the effect of variations in ambient temperature as determined by the temperature sensor, and optional means for reducing interference by moving parts of the vehicle to which it is mounted. The present invention also provides methods of using the improved vehicle sonar device and for calculating one or more plant yield characteristics.

Description

Crop meter and uses therefor Related application data

The present application claims Convention priority from Australian Patent Application No. 2007903132 filed June 12, 2007 and Australian Patent Application No. 2008901599 filed April 3, 2008 the contents of which are incorporated herein in their entirety by way of reference.

Field of the invention

The present invention relates to the field of agriculture and more particularly to ultrasonic devices for determining crop (e.g., food crop or pasture crop) yield and/or sward height such as for harvest or grazing purposes.

Background to the invention

Crop (e.g., food crop or pasture crop) yields are important for determining the amount of harvestable crop product and for determining the amount of fodder available for grazing livestock. Accurate determination of yield is important for deciding harvest time, timing of fertilizer application, optimising grazing to maximize productivity of grazing animals. Optimising feed yields significant benefits in terms of productivity of grazing animals e.g., milk yield and carcass weight of cattle, and underestimating or over-estimating the amount of feed available in a particular pasture can be costly in terms of reduced productivity.

In terms of dairy cattle, many farmers attempt to avoid low productivity by overfeeding their cowherds. While this avoids a reduction in milk production, it often results in wastage of feed that could have been used to feed other herds e.g., in neighboring pastures of lower yield. To optimise grazing performance over several pastures, it is necessary to determine the amount of pasture or grass in each field.

Conventionally, the height of the grass or pasture is estimated using a plate meter, which may be a manual rising plate meter or electronic rising plate meter. A manual rising plate meter generally comprises a shaft fitted with a sliding plate and two mechanical counters. One counter measures the numbers of measurements taken ("plonks") and the other counter measures the movement on the shaft (i.e., pasture height of "clicks"). The metal shaft is generally graduated into 0.5 cm grooves, each being a "click"). In use, the plate is placed ("plonked") squarely on the ground at regular intervals e.g., every 5 paces, to reduce variation. In each plonk, the plate rests on top of the pasture providing a compressed height value in 0.5 cm gradations on the lower counter. Such readings depend upon the plate weight being equal to the pressure of the compressed pasture stopping the plate from lowering to the ground. At each plonk, the user clicks the top counter to record the total number of samples taken. Generally, 20-40 plonks are made per paddock, however this varies considerably depending upon the variance in pasture cover for the paddock. Pasture cover may then be averaged as a compressed height value over the number of plonks. The accuracy of the plate meter depends upon the user maintaining a consistent pace, ensuring that the meter is vertical to the ground, and avoiding any rolling movement. An electronic rising plate meter is based on the same principle as the manual rising plate meter, however comprises an electronic counter and uses capacitance to sense each time a reading is made from a plonk. The electronic plate meter also updates the average height for the paddock after each plonk. The electronic rising plate meter will generally provide pasture cover data by transforming pasture compressed height data into pasture yield data expressed as kilograms of dry matter per hectare (i.e., "kg DM/ha") or other appropriate yield measurement.

SONAR (i.e., sound navigation and ranging) is known to be useful for detecting plants. A sound signal or wave is generated, and transmitted by an ultrasonic transmitter toward the top of a crop or pasture, and then an echo signal or wave is reflected back to an ultrasonic receiver, and the time it takes for the sound signal to reach the plant head and for the echo to return is used to calculate the distance of the plant head from the sensor.

The predominance of public disclosures relating to the use of ultrasonic devices in agriculture relate to the use of SONAR to maintain the height of agricultural equipment from the ground, and these have met with variable success in contexts involving growing plants. For example, an ultrasonic sensor for maintaining the height of cutters for chicory, tomato, sugarcane and wheat crops have been described. Such devices do not generally require the same degree of accuracy as a device for determining yield parameters, since they merely need to approximate the height of a cutter during harvest. As a consequence, they do not generally take account of those parameters affecting the speed of sound in crops and pastures e.g., temperature, crop density, etc. Nor do they need to take account of variations in terrain and crop/pasture density. Although ultrasonic (SONAR) devices have also been described for measurement of crop (e.g., food crop or pasture crop) plant growth and yield parameters, they have met with variable success and largely found to be unsuitable or inaccurate. For example, an ultrasonic device has been described for determining maize canopy measurements, however the sensor of this device merely records the sizes of individual leaves and determines growth stage of plants from those measurements, and does not provide information on the crop yield per se. An ultrasonic device has also been described for determining height of plants for optimising spraying height for a boom sprayer, however was found to be accurate only for broadleaf plants, as opposed to grasses which produced erroneous height readings due to a decrease in the reflected echoes that were recorded.

In work leading up to the present invention, the inventors sought to ascertain the reasons for poor accuracy of SONAR devices in determining crop (e.g., food crop or pasture crop) yield. For example, the inventors have found that there are significant diurnal and seasonal variations in temperature on crops and pastures which can produce errors of as much as 10% in crop/pasture mass determinations. Moreover, without accounting for such fluctuations in temperature, accurate determinations can only be made for crops and pastures at under near-identical temperatures e.g., at the same time of day and same season. Additionally, as crops are not static, but move under the force of wind and other climatic conditions, considerable noise can be generated using SONAR on crops and pastures, making it difficult to determine the start point of a main echo for the distance calculation. Other echoes from crops and pastures may be weak yet rapid, contributing to significant noise. In vehicle-mounted SONAR devices, echo noise may also be contributed by the transmitted sound signal swamping the area below it, including vehicle components, as opposed to the signal being transmitted predominantly or only to the crop or pasture. Pasture density also contributes to significant variation in echo strength and reproducibility and, as a consequence accuracy of SONAR devices in determining crop (e.g., food crop or pasture crop) yield data. For example, yield will be contributed predominantly by height of a grass crop or pasture, whereas echoes may be returned from leaves below grazing height, from lateral leaves and leaves lying sideways below the top of the crop or pasture. Summary of the invention

The present invention provides a sonar device for determining a plant yield characteristic that solves one or more of the foregoing problems identified by the inventors.

By way of example, the following statements summarize the features of the present invention:

In one example, the present invention provides a sonar device for determining one or more plant yield characteristics, wherein the device comprises: a) an ultrasonic transmitter for transmitting timed pulses of ultrasonic energy towards plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) an ultrasonic receiver for receiving reflected echoes of the transmitted timed pulses from the plant material; c) a temperature sensor; d) a signal pre-processing means for determining reflected main echoes of the transmitted timed pulses from the plant material; and e) one or more computational means for calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes, the distance(s) from the transmitter to the plant material from the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes and for determining one or more plant yield characteristics from said distance(s), wherein said computational means comprises an algorithm that corrects for the effect of variations in ambient temperature as determined by the temperature sensor; and wherein the device is mountable on a vehicle travelling above the surface of the plant material.

The sonar device may further comprise means for entering data in relation to the plant material e.g., a touch screen pad or key pad.

The sonar device may further comprise means for displaying data in relation to the plant material and/or distance(s) and/or one or more plant yield characteristics e.g., an LCD display. The sonar device may further comprise one or more of the following features separately or in combination:

(i) a sensor driver e.g., a 10V or a 36V driver device;

(ii) a microcontroller or sensor microprocessor that controls the timed pulses of ultrasonic energy produced by the ultrasonic transmitter; (iii) an analog-to-digital converter (ADC);

(iv) a global positioning system (GPS) for receiving and/or processing and/or displaying data pertaining to the location of plant material e.g., latitude and/or longitude and/or elevation data; and (v) an imaging means for transforming data into a 2-dimensional or 3-dimensional representation and displaying the representation;

In certain examples, the ultrasonic transmitter transmits pulses of ultrasonic energy having a frequency above about 20 kHz and/or the ultrasonic receiver is configured to receive echoes above about 20 kHz.

In certain examples, the temperature sensor comprises a thermistor or thermocouple.

In certain examples, the signal pre-processing means comprises one or more components selected from the group consisting of a preamplifier, a bandpass filter, a precision rectifier, an envelope follower and an analog-to-digital converter (ADC) e.g., a Flash ADC. In certain examples, the signal pre-processing means comprises an ADC. In certain examples, the signal pre-processing means comprises an ADC, an analog pre-processor, digital signal processor (DSP) and a communications or storage device. In certain examples, the signal pre-processing means comprises a preamplifier. In certain examples, the signal pre-processing means comprises a bandpass filter. In certain examples, comprises a precision rectifier e.g., a full-wave precision rectifier or a half-wave precision rectifier. In certain examples, the signal pre-processing means comprises an envelope follower. In certain examples, the signal pre-processing means comprises a preamplifier and a bandpass filter. In certain examples, the signal preprocessing means comprises a preamplifier, a bandpass filter, a precision rectifier, an envelope follower and an analog-to-digital converter (ADC).

In certain examples, the one or more computational means comprise(s) a central processing unit (CPU), or one or more microprocessor cores comprising a plurality of central processing units (CPUs), or a microcontroller comprising a central processing unit (CPU), or a sensor controller, or a system-on-a-chip (SoC), or a digital signal processor (DSP), or a nanoprocessor. In certain examples, the CPU is a 6-bit, 16-bit, 32-bit, 64-bit, 128-bit or 256-bit CPU. In certain examples, the one or more computational means has a programmable facility.

In certain examples, the components of the sonar device are provided in two units or boxes and wherein one or more components of one of said units or boxes is(are) in communication with one or more components of the other of said units or boxes e.g., by means of a communications cable, data cable or wireless means. For example, the components of said sonar device can be provided in a sensor head box and an interface box and wherein one or more components of said sensor head box is(are) in communication with one or more components of said interface box e.g., by means of a communications cable, data cable or wireless means. In certain examples, the sensor head box and/or interface box is/are constructed of water-resistant or moisture-resistant material.

In certain examples, the sensor head box comprises the ultrasonic transmitter and ultrasonic receiver. In certain examples, the sensor head box comprises the temperature sensor. In certain examples, the sensor head box comprises the signal pre- processing means. In certain examples, the sensor head box comprises the sensor driver. In certain examples, the sensor head box comprises the microcontroller or microprocessor for controlling timed pulses of ultrasonic energy produced by the ultrasonic transmitter. In certain examples, the sensor head box comprises the analog- to-digital converter (ADC).

In certain examples, the interface box comprises the one or more computational means. In certain examples, the interface box comprises the means for entering data. In certain examples, the interface box comprises the means for displaying data. In certain examples, the interface box comprises the microcontroller or microprocessor for controlling timed pulses of ultrasonic energy produced by the ultrasonic transmitter. In certain examples, the interface box comprises the temperature sensor.

In certain examples, the ultrasonic transmitter is mounted at an angle within the sensor head box sufficient to provide an angle of transmitted waves of up to about 20 degrees relative to the longitudinal shoot axis of plants. For example, the end face of the sensor head box can be bevelled so as to provide an angle of transmitted waves of up to about 20 degrees relative to the longitudinal shoot axis of plants when the face of the ultrasonic transmitter is in the same plane as the bevelled end face of the sensor head. Alternatively, or in addition, the ultrasonic transmitter can be recessed within the sensor head e.g., adjustably recessed within the sensor head to thereby restrict the cone width of the timed pulses of ultrasonic energy.

In certain examples, the ultrasonic receiver is directed to the plant material at about the same angle as the ultrasonic transmitter.

In certain examples, the ultrasonic receiver is in the same plane as the ultrasonic transmitter.

In certain examples, the ultrasonic receiver is in a different plane to the ultrasonic transmitter. For example, the ultrasonic receiver can be adjustably recessed within the sensor head relative to the ultrasonic transmitter to thereby restrict the cone width of the echoes received. In certain examples, the ultrasonic receiver is recessed a sufficient distance to reduce or prevent interference from structures of a vehicle to which it is mounted.

In certain examples, pulses of ultrasonic energy are at predetermined regular intervals e.g., wherein a predetermined regular interval is predetermined with respect to a condition selected from crop species, density, variability in crop cover, and climatic condition. In one example, a predetermined regular interval is less than about one minute.

In certain examples, timed pulses of ultrasonic energy are less than about 20 pulses per second.

In certain examples, the device is used to determine a plant yield characteristic selected from plant height and dry matter weight per unit area. Combinations of plant yield characteristics are also determined using the device.

In certain examples, the sonar device is mounted on a vehicle travelling above the surface of the plant material and wherein the vehicle is a powered vehicle selected from the group consisting of a tractor, motor bike, and truck. In certain examples, the sonar device is mounted on a vehicle travelling above the surface of the plant material and wherein the vehicle is a bicycle or other pedal-driven vehicle.

In certain examples, the sonar device is mounted on a trailor, trolley, sledge or wheeled frame that is attached to and driven by powered or non-powered vehicle.

In certain examples, the sonar device of the present invention includes means for correcting for variations in vehicle height arising from a variation in vehicle height e.g., as a consequence of load on the vehicle or a variation in terrain e.g., e.g., a change in terrain slope, a depression or incline. In certain examples, the sonar device comprises means for correcting for a variation in vehicle height such as, for example, a computational means that may be an algorithm that modulates sensor height in response to a variation in compression and/or de-compression of a vehicle suspension, or alternatively, an algorithm that corrects for a variation in compression and/or decompression of a vehicle suspension in response to a variation in vehicle height. In one example, said means comprises an adjustable sensor height wherein the sensor height is adjusted in response to a variation in vehicle height e.g., as a result of compression or de-compression of vehicle suspension. In one example, the sensor height is raised when the gradient of the terrain reduces i.e., becomes less positive or negative, as the vehicle moves from a first position to a second position. For example, the sensor height may be raised when the vehicle moves from a first position to a second position that is downward facing relative to the first position or when the vehicle moves from a first upward facing position to a second level or downward facing position. In another example, the sensor height is lowered when the gradient of the terrain increases i.e., becomes more positive or less-negative, as the vehicle moves from a first position to a second position. For example, the sensor height may be lowered when the vehicle moves from a first position to a second position that is upward facing relative to the first position or when the vehicle moves from a first downward facing position to a second level or upward facing position. In certain examples, the compression or decompression of the vehicle suspension raises or lowers the height of the sensor. For example, a vehicle suspension may raise the sensor when the vehicle travels up an inclination e.g., a hill. For example, a vehicle suspension may lower the sensor when the vehicle travels down a slope. In one example, said means for correcting for variations in vehicle height arising from a variation in vehicle height comprises a computational means for determining a compression and/or de-compression of a vehicle suspension in response to a change in vehicle height.

In certain examples, the sonar device of the present invention includes means for correcting for variations in crop height or other yield parameter arising from a variation in terrain e.g., uneven terrain, a hole, mound, or slope. In certain examples, the sonar device comprises means for correcting for a variation in terrain topography, such as e.g., computational means that may comprise an algorithm that modulates sensor height in response to a variation in terrain topography or alternatively, comprises an algorithm that corrects for a variation in terrain topography. In one example, said means comprises an adjustable sensor height wherein the sensor height is adjusted at the point where a variation in terrain, e.g., a change in terrain slope, a depression or incline, is detected. In one example, the sensor height is raised when the gradient of the terrain reduces i.e., becomes less positive or negative, as the vehicle moves from a first position to a second position. For example, the sensor height may be raised when the vehicle moves from a first position to a second position that is downward facing relative to the first position or when the vehicle moves from a first upward facing position to a second level or downward facing position. In another example, the sensor height is lowered when the gradient of the terrain increases i.e., becomes more positive or less-negative, as the vehicle moves from a first position to a second position. For example, the sensor height may be lowered when the vehicle moves from a first position to a second position that is upward facing relative to the first position or when the vehicle moves from a first downward facing position to a second level or upward facing position.

It follows from the foregoing that, in certain examples, the sonar device may comprise a sensor head box mounted on the front, rear or sides of a vehicle such that the transmitted timed pulses of ultrasonic energy are capable of being directed towards plant material without interference from vehicle components. In certain examples, an interface box mounted on a vehicle such that it is in view of the operator of the vehicle.

It also follows from the foregoing that the present invention is directed to the use of a sonar device according to any example hereof in the determination of one or more plant yield characteristics e.g., plant height and/or dry matter weight per unit area, optionally wherein said yield characteristic is determined and/or expressed with reference to location of plant material and/or a specified period of time e.g., season, day, month, year, etc.

More specifically, in one example, the present invention provides a method for determining one or more plant yield characteristics comprising: a) transmitting one or more pulses of ultrasonic energy towards the plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) receiving reflected echoes of the transmitted timed pulses from the plant material; c) determining ambient temperature; d) determining reflected main echoes of the transmitted timed pulses from the plant material; e) calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes wherein said time is corrected for the effect of variations in ambient temperature as determined at (c); f) calculating the distance(s) from the transmitter to the plant material from the corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes; and g) determining one or more plant yield characteristics from said distance(s).

In another example, the present invention provides a process for determining one or more plant yield characteristics comprising: i) providing a sonar device according to any example hereof; and ii) determining one or more plant yield characteristics by employing said sonar device in a method comprising: a) transmitting one or more pulses of ultrasonic energy towards the plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) receiving reflected echoes of the transmitted timed pulses from the plant material; c) determining ambient temperature; d) determining reflected main echoes of the transmitted timed pulses from the plant material; e) calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes wherein said time is corrected for the effect of variations in ambient temperature as determined at

(C); f) calculating the distance(s) from the transmitter to the plant material from the corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes; and g) determining one or more plant yield characteristics from said distance(s).

In certain examples, the process of the invention comprises providing the sonar device with instructions as to use of said device in the determination of the one or more plant yield characteristics.

In certain examples, the method or process of the present invention further comprises displaying data in relation to the distance(s) and/or one or more plant yield characteristics. In certain examples, the method or process of the present invention further comprises entering data in relation to the plant material. Exemplary data in relation to the plant material are selected from sowing density, fertilization regime, watering regime, grazing intensity, harvest data, height-to-dry matter correlation, dry weight-to-fresh weight ratio, plant source, plant species, plant compositional data, nutrient data, seasonal variation data, terrain data and location data.

In certain examples, the method or process of the present invention comprises determining the one or more plant yield characteristics with reference to one or more locations of plant material and/or with reference to a specified period of time e.g., season, month, day, year, etc.

As will be apparent from the preceding description, the plant yield characteristic may be, for example, plant height or dry matter weight per unit area.

In certain examples, the method or process of the present invention is applied to determining one or more yield characteristics in a crop plant e.g., a food crop plant, an oilseed crop plant or a pasture crop plant. In certain examples, the food crop plant is a grain crop plant, a vegetable or a fruit-bearing plant. In certain examples, the grain crop plant is selected from maize, wheat, rice, rye, millet, sorghum, barley, quinoa and sugarcane. In certain examples, the vegetable is selected from sugar beet and chicory. In certain examples, the fruit-bearing plant is selected from tomato, apple, orange, mandarin and other citrus. In certain examples, the oilseed crop plant is selected from canola, rapeseed, jojoba, meadow foam, flax, soybean, sunflower, cotton, corn, olive, safflower, cocoa and peanut. In certain examples, the pasture crop plant is a grass plant. In certain examples, the grass plant is selected from a perennial grass, annual grass or bunchgrass plant. In certain examples, the grass plant is selected from bent grass, fescue, ryegrass, weeping grass, orchard grass, brome grass, canary grass, lucerne, kikuyu, paspalum, prairie grass, gamba grass, Surinam grass, buffel grass, Rhodes grass, bermuda grass, pangola grass, weeping love grass, jaragua, molasses grass, guinea grass, napier grass, setaria grass and mixtures thereof. In certain examples, the pasture crop plant is selected from the group consisting of clover, lucerne, kikuyu, paspalum, prairie grass and mixtures thereof.

Brief description of the drawings

The present invention is further described with reference to the following non-limiting drawings.

Figure 1 is a copy of a photographic representation showing the arrangement of a sonar device of the present invention comprising a sensor head box (4) and interface box (2) mounted on an all-terrain vehicle. The sensor head box and interface box are connected by a communications cable. Curved lines indicate the ultrasonic pulses transmitted from the sensor head box.

Figure 2 is a schematic representation showing the circuit layout connecting functional components of an exemplified sonar device of the present invention. In the drawing, sensor head box (4) comprises an ultrasonic transmitter (10) driven by a 36V sensor driver (12), which transmits pulses of ultrasonic energy from the sensor head box under control of a microcontroller (32) positioned within interface box (2). Echoes are received from plant material by an ultrasonic receiver (16) positioned within the sensor head box (4). The echo signal is pre-processed by a pre-processing means comprising a circuit positioned between the ultrasonic receiver (16) and the microcontroller (32), said circuit comprising a preamplifier (18), a 40 kHz bandpass filter (22), a half-wave precision rectifier (24), an envelope follower (26) and ADC (28) in series. A temperature sensor (30) records ambient temperature and transmits temperature data to the microprocessor (32) for determination of the speed of sound at that temperature. The processed signal is digitised by ADC (28) and transmitted to the microprocessor (32) for calculation of yield characteristic data from data on the average temperature- corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes. A keypad (8) permits data entry, and a LCD display (6) permits display of entered data and/or stored data and/or calculated yield data.

Figure 3 is a copy of photographic representations showing lateral views of the unmounted sensor head box (top left and right) and sensor head box as mounted on an all-terrain vehicle (lower), with the bevelled end-face of the sensor head showing the arrangement of the ultrasonic transmitter and ultrasonic receiver.

Figure 4 is a schematic representation showing the circuit layout connecting functional components of an exemplified sonar device of the present invention. In the drawing, an ultrasonic transmitter (10) driven by a 10V sensor driver (12) transmits pulses of ultrasonic energy from the sensor head box under control of a sensor microprocessor (34). Echoes are received from plant material by an ultrasonic receiver (16). The echo signal is pre-processed by a pre-processing means comprising a circuit positioned between the ultrasonic receiver (16) and the microprocessor (34), said circuit comprising a preamplifier (18) and a 40 kHz bandpass filter (22) in series. A temperature sensor (30) records ambient temperature and transmits temperature data to the sensor microprocessor (34) for determination of the speed of sound at that temperature. The processed signal is transmitted to the sensor microprocessor (34) for calculation of yield characteristic data from data on the average temperature-corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes. An external hardware interface (36) communicates bidirectionally with the sensor microprocessor (34).

Figure 5 is a schematic representation showing an example of programming logic for calculating distance (d) from the sensor head to the plant material from data on the average temperature-corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes. Analog data are input to a signal rectifier (24) and envelope follower (26) to thereby provide a differential of a sine wave wherein: I is the index of a sample, initialised to zero at the start of a pulse (i.e., a "Ping"); the sample index increments by unitary values such that I₁= Io +1; M is the maximum sample count calculated from the sample rate and maximum reading distance of the device; there is a buffer of N samples wherein N is a positive value and wherein N=I indicates no smoothing of the signal and wherein the value of N is directly proportional to degree the signal is smoothed by the envelope follower; and Y is a differential of a filtered sample calculated by dy/dt i.e., the rate of change in sample amplitude for samples taken over time. If the differential of the sine wave for any sample index value less than the maximum sample count, pulses that fail to record an echo e.g., because the sample pulse is at a distance greater than the maximum distance read, are excluded. For echoes that are pre-processed and for which the differential of the sine wave exceeds a user-defined trigger point (TP) i.e., Y > TP, the distance (d) from the sensor head to the plant material is calculated as a function of the temperature- corrected speed of sound at ambient temperature (S) and the distance from the sensor head to the ground as determined from a tare reading (t) i.e., d = t x S.

Figure 6 is a schematic representation showing an example of programming logic for calculating dry matter from distance of the sensor head to the plant material. Analog data are input to a bandpass filter (22) that checks for each sample, the distance (d) is within user-defined upper (H) and lower (L) boundaries for distance of the sensor head to the plant material. For example, the lower distance might be a tared distance value from the sensor head to the ground and the upper value might be the tare value plus a user-defined maximum distance for the crop at the particular time of year or season, or under particular grazing conditions. Only samples that produce echoes for which the criterion L < d > H applies pass the bandpass filter, in which case distance (d) is added to the total distance increment ping counter and used for dry matter calculation. In this calculation, dry matter (DM) is calculated as a function of the average distance (D) (calculated over a given number of pings as determined by the ping counter i.e., D= total distance /ping count) and a user-defined constant (A) dependent on the crop and season. The correlation of dry matter (DM) to distance is also affected by one or more other constants (B) e.g., that explain variation between actual dry matter and predicted dry matter, such that DM = D x A + B. The success rate may also be calculated.

Figure 7 is a copy of a graphical representation showing pre-processing of an analog signal by the preamplifier (40), bandpass filter (42), half-wave precision rectifier (44) and envelope follower (46) in the signal pre-processing circuit shown in Figure 2 hereof.

Figure 8 is a copy of a graphical representation showing pre-processing of a sample analog signal (50) to produce a derivative thereof (54) to thereby permit determinations of a start point for a main reflected echo (arrow). Figure 9 is a schematic representation showing a cross-sectional view of an exemplary sensor head (4) of the sensor device of the present invention. Numbering is as shown in Figures 1 to 4. In this example, a sensor head box (4) comprises an ultrasonic transmitter (10) driven by a sensor driver (12) that transmits pulses of ultrasonic energy from the sensor head box (4) under control of a sensor microprocessor (34). Echoes are received by an ultrasonic receiver (16) that is recessed in the sensor head box relative to the ultrasonic transmitter (10). Such recessing of the ultrasonic receiver (16) produces a narrower cone width for the echo than for the transmitted pulses, filtering unwanted echoes arising from objects in the excluded cone width. The faces of the sensors are shown parallel to each other. The narrowed echo signal is pre-processed by a preprocessing means comprising a circuit positioned between the recessed ultrasonic receiver (16) and the microprocessor (34), said circuit comprising a preamplifier (18) and a 40 kHz bandpass filter (22) in series. A temperature sensor (30) positioned outside the sensor head (4) records ambient temperature and transmits temperature data to the sensor microprocessor (34) for determination of the speed of sound at that temperature. The processed signal is transmitted to the sensor microprocessor (34) for calculation of yield characteristic data from data on the average temperature-corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes. An external hardware interface (36) communicates bidirectionally with the sensor microprocessor (34).

Figure 10 is a schematic representation showing the sequential display and data entry fields of an exemplary interface box of the sonar device. A first window (a) provides optional device model number, software data and patent information for the device, and permits configuration of the device and entry of field or paddock details. Selection of the "Edit paddock details" key opens a second window (b) that permits entry and display of data in relation the crop e.g., paddock of field number. Crop species or mixture of crop species growing on the paddock or field, paddock or field size, number of animals grazing on the paddock or field, and seasonal data such as percentage of dry matter for the crop at the particular time of year, and dry matter compensation. Other data may also be entered in relation to the crop. Once paddock details are entered they may be saved to memory. To commence reading, the "Start Reading" key is pressed and this opens a third window (c) that permits a further selection of taring of the device or crop reading to be undertaken. Taring of the device is performed on one or more freshly mown or already-harvested sections of the field or paddock to thereby determine the distance of the sensor head to the ground. Crop reading is undertaken on unharvested plant material growing in the field or paddock. By selecting the "Tare" option, data obtained from the device will automatically be stored as a "Tare Distance" values. If the field or paddock has been tared previously, or the user otherwise intends not to tare, the "Bypass Tare" option is selected to permit the device to determine distances from the sensor head to the plant material growing in the field or paddock. By selecting the "Bypass Tare" option, data obtained from the device will automatically be stored as a "Pasture Height" values. An indicator at the lower edge of window (c) shows the progress of taring or crop reading as appropriate. When the taring or crop reading is in progress or complete, window (d) may be opened showing the progress of readings and/or the final readings taken, including, for example, the number and/or percentage of successful readings; average Tare Distance; Crop Height; Average Crop Height; Correlation equation used to determine crop height from echo data according to the formula DM = D x A + B; Available Paddock Dry Matter as determined from the total dry matter per unit area; and Available Paddock Dry Matter as determined from the total dry matter per grazing animal. Data presented in window (d) may be continuously updated during reading. When reading is completed, such as determined by the percentage of successful readings reaching an acceptable level, reading is stopped by pressing the "STOP" key. A fifth window (e) opens when readings are stopped, which permits selection of subroutines for saving or deletion of recorded data, with the option of returning to window (a) for entering additional paddock or field information and reading or recording additional paddocks or fields, thereby permitting iterative use of the device over several fields or paddocks or at different locations within the same field or paddock. It is also possible in window (e) to select "View Saved Data" which opens window (f) displaying the saved data.

Figure 11 is a graphical representation showing the effect of varying the sensor angle from 10 degrees to 20 degrees on the correlation between height of kikuyu pasture sward and pasture yield calculated as kilograms dry matter per hectare. Data indicate that 10 degree and 15 degree sensor angles provide superior correlations compared to a 20 degree sensor angle, as determined by the correlation coefficient R values.

Figure 12 is a graphical representation showing the correlation between height of pasture sward and pasture yield calculated as kilograms dry matter per hectare for two different lucerne cultivars. Correlation coefficient R² values indicate strong correlations in both cases when a 15 degree sensor angle is employed, comparable to those obtained and shown in Figure 11 for kikuyu. Figure 13 is a graphical representation showing the correlation between height of pasture sward and pasture yield calculated as kilograms dry matter per hectare for paspalum. The correlation coefficient R² value indicates a strong correlation when a 15 degree sensor angle is employed, slightly lower than that obtained and shown in Figure 11 for kikuyu.

Figure 14 is a graphical representation showing the correlation between height of pasture sward and pasture yield calculated as kilograms dry matter per hectare for prairie grass. The correlation coefficient R² value indicates a strong correlation when a 15 degree sensor angle is employed, slightly lower than that obtained and shown in Figure 11 for kikuyu.

Figure 15 is a graphical representation showing the correlation between height of pasture sward as calculated using the sonic device of the present invention and pasture yield calculated as kilograms dry matter per hectare from actual mower cuts. Data represent combined values for several pasture species. The correlation coefficient R² value indicates a strong correlation between readings obtained using the sonic device of the present invention and actual mower cut yield values.

Figure 16 is a graphical representation showing the correlation between height of pasture sward as calculated using a hand held plate meter device and pasture yield calculated as kilograms dry matter per hectare from actual mower cuts. Data represent combined values for several pasture species. The correlation coefficient R² value indicates a strong correlation between readings obtained using a plate reader and actual mower cut yield values, albeit lower than the correlation obtained using the sonic device of the present invention and actual mower cut yield values (Figure 15).

Figure 17 is a graphical representation showing the correlation between height of pasture sward and pasture yield calculated as kilograms dry matter per hectare as calculated using the sonic device of the present invention set at 10 readings per second. Data represent combined values for several pasture species. The correlation coefficient R² value indicates a strong correlation between pasture height and dry matter yield.

Figure 18 is a graphical representation showing the correlation between pasture yield calculated from mower cuts and pasture yield calculated as kilograms dry matter per hectare as calculated using the sonic device of the present invention. Data represent combined values for several pasture species. The correlation coefficient R value indicates a strong correlation between dry matter yields calculated from mower cuts and dry matter yields calculated using the device of the invention.

Detailed description of the preferred embodiments Exemplary device of the invention

In a first example, the present invention provides a sonar device for determining one or more plant yield characteristics, preferably plant height or dry matter weight per unit area, wherein the device comprises: a) an ultrasonic transmitter for transmitting timed pulses of ultrasonic energy towards plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) an ultrasonic receiver for receiving reflected echoes of the transmitted timed pulses from the plant material; c) a temperature sensor; d) a signal pre-processing means for determining reflected main echoes of the transmitted timed pulses from the plant material; and e) one or more computational means for calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes, the distance(s) from the transmitter to the plant material from the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes and for determining one or more plant yield characteristics from said distance(s), wherein said computational means comprises an algorithm that corrects for the effect of variations in ambient temperature as determined by the temperature sensor; and wherein the device is mountable on a vehicle travelling above the surface of the plant material.

In a second example, the present invention provides a sonar device for determining one or more plant yield characteristics, preferably plant height or dry matter weight per unit area, wherein the device comprises: a) an ultrasonic transmitter for transmitting timed pulses of ultrasonic energy towards plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) an ultrasonic receiver for receiving reflected echoes of the transmitted timed pulses from the plant material; c) a temperature sensor; d) a signal pre-processing means for determining reflected main echoes of the transmitted timed pulses from the plant material; e) one or more computational means for calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes, the distance(s) from the transmitter to the plant material from the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes and for determining one or more plant yield characteristics from said distance(s), wherein said computational means comprises an algorithm that corrects for the effect of variations in ambient temperature as determined by the temperature sensor; and f) means for entering data in relation to the plant material; and wherein the device is mountable on a vehicle travelling above the surface of the plant material.

In a third example, the present invention provides a sonar device for determining one or more plant yield characteristics, preferably plant height or dry matter weight per unit area, wherein the device comprises: a) an ultrasonic transmitter for transmitting timed pulses of ultrasonic energy towards plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) an ultrasonic receiver for receiving reflected echoes of the transmitted timed pulses from the plant material; c) a temperature sensor; d) a signal pre-processing means for determining reflected main echoes of the transmitted timed pulses from the plant material; e) one or more computational means for calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes, the distance(s) from the transmitter to the plant material from the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes and for determining one or more plant yield characteristics from said distance(s), wherein said computational means comprises an algorithm that corrects for the effect of variations in ambient temperature as determined by the temperature sensor; and f) means for displaying data in relation to the distance(s) and/or one or more plant yield characteristics; and wherein the device is mountable on a vehicle travelling above the surface of the plant material.

In a fourth example, the present invention provides a sonar device for determining one or more plant yield characteristics, preferably plant height or dry matter weight per unit area, wherein the device comprises: a) an ultrasonic transmitter for transmitting timed pulses of ultrasonic energy towards plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) an ultrasonic receiver for receiving reflected echoes of the transmitted timed pulses from the plant material; c) a temperature sensor; d) a signal pre-processing means for determining reflected main echoes of the transmitted timed pulses from the plant material; e) one or more computational means for calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes, the distance(s) from the transmitter to the plant material from the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes and for determining one or more plant yield characteristics from said distance(s), wherein said computational means comprises an algorithm that corrects for the effect of variations in ambient temperature as determined by the temperature sensor; f) means for entering data in relation to the plant material; and g) means for displaying data in relation to the plant material and/or distance(s) and/or one or more plant yield characteristics; and wherein the device is mountable on a vehicle travelling above the surface of the plant material.

Angle of transmitted pulses of ultrasound

In use, timed pulses of ultrasonic energy are directed towards plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants.

Strict compliance with the range of angles for the transmitted pulses of ultrasound is not required, especially given the variations in crop and morphology and terrain for most crop plants. Accordingly, ranges of between 7 degrees and 23 degrees are acceptable for most field applications. Preferably, transmitted timed pulses of ultrasonic energy are capable of being directed towards plant material at an angle of between about 10 degrees and about 20 degrees relative to the longitudinal shoot axis of plants, or between about 10 degrees and about 15 degrees relative to the longitudinal shoot axis of plants, or between about 15 degrees and about 20 degrees relative to the longitudinal shoot axis of plants. In a particularly preferred embodiment suitable to most pasture crops including mixed pastures, transmitted timed pulses of ultrasonic energy are capable of being directed towards plant material at an angle of about 15 degrees relative to the longitudinal shoot axis of plants.

The desired angle of the transmitted ultrasonic waves can be readily achieved by mounting the ultrasonic transmitter at an appropriate angle within a sensor head box to provide the appropriate angle of transmitted waves. Preferably, the end face of a sensor head box is bevelled to the appropriate angle such that, when the face of the ultrasonic transmitter is in the same plane as the end face of the sensor head, the angle of transmitted ultrasonic waves emitted from the transmitter is correct. It is to be understood in this context that the face of the ultrasonic transmitter need not be flush with the end face of a sensor head, and may even be recessed within a sensor head.

Timing of pulses

In use, the pulses of ultrasonic energy are "timed". As used herein, the term "timed pulses" means that ultrasonic energy is transmitted as pulses of sound at regular intervals, which may be predetermined and vary according to the particular conditions e.g., crop species, density, variability in crop cover, and climatic conditions. The maximum number of timed pulses per unit time (e.g., pulses per second) is constrained by the requirement for the face of the ultrasonic transmitter to stabilize between each pulse and for the face of the ultrasonic receiver to stabilize between each received echo, since a greater number of timed pulses per unit time will generally adversely affect the ability to distinguish main echoes from noise. The minimum number of timed pulses per unit time (e.g., pulses per second) is subject to the need to return statistically- significant mean data in a reasonable period of time to determine a crop profile e.g., in less than about one minute and preferably in less than about 30 seconds or less than about 20 seconds or in about 10 seconds. Preferably, timed pulses are less than about 20 pulses per second and more preferably less than about 15 or 16 pulses per second. Even more preferably, time pulses are less than about 10 pulses per second and still more preferably, at about 5 to about 10 pulses per second, including 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 11 or 12 pulses per second.

Angle of received echoes

In use, an ultrasonic receiver receives reflected echoes of the transmitted timed pulses from the plant material.

It will be understood be the skilled artisan that the ultrasonic receiver should be directed to the plant material at about the same angle as the ultrasonic transmitter for optimal reception of echoes from the plant material, albeit not necessarily in the same plane as the ultrasonic transmitter.

Frequency range

Preferably, the ultrasonic transmitter transmits pulses of ultrasonic energy having a frequency above 20 kHz and more preferably at about 40 kHz.

Preferably, the ultrasonic receiver is configured to receive echoes above about 20 kHz and more preferably, it is centred on about 40 kHz.

Sensor head box and interface box

Conveniently, the components of the device are provided as two units or boxes i.e., a sensor head box and an interface box, that are connected by means of a communications cable or data cable, or alternatively, by wireless means.

Preferably, the sensor head box and/or interface box is/are made of water-resistant or moisture-resistant material e.g., plastic or metal.

Temperature sensor

The sonar device of the present invention comprises a temperature sensor. In use, the temperature sensor obtains and feeds temperature data to a computational means that comprises an algorithm that corrects for the effect of variations in ambient temperature as determined by the temperature sensor. The temperature sensor may comprise a thermistor, thermocouple, or the like, and be positioned within a sensor head or external to it e.g., in an interface box. In fact, the inventors have found that it is not necessary for the temperature sensor to be positioned near to the ultrasonic sensors, since there is little variation in ambient temperature between the sensor head and interface box at any given time, the only requirement being that sufficient time is provided for the temperature sensor to record the ambient temperature before taking readings for determining crop yield data.

The temperature sensor is preferably connected by a lead wire to the one or more computational means to thereby permit ambient temperature effects to be taken into consideration by an algorithm that corrects for the effect of variations in ambient temperature on the speed of sound. In one example, the connection between the temperature sensor and one or more computational means is indirect, with an intervening ADC positioned between these components. In another example, the connection between the temperature sensor and one or more computational means is direct, by wired electrical or wireless means.

Signal pre-processing means

The sonar device of the present invention comprises a signal pre-processing means for determining reflected main echoes of the transmitted timed pulses from the plant material.

The signal pre-processing means provides for signal modulation and analog-to-digital conversion to thereby permit the computational means to determine main reflected echoes. By "main reflected echo" is meant a true echo reflected from the crop and substantially free of noise arising e.g., from the movement of the crop, lateral tillers within the crop, variable crop density, vehicle parts, etc. The signal pre-processing means comprises one or more components selected from the group consisting of a preamplifier, a bandpass filter, a precision rectifier, an envelope follower and optionally an analog-to-digital converter (ADC) connected serially to the ultrasonic receiver, including all components in combination. Generally connections between the various components of the signal pre-processing means are wired to each other and to the ultrasonic receiver.

In one example, a sensor device of the present invention utilizes a signal pre-processing means that provides for analog pre-processing and analog to digital conversion. A preferred signal pre-processing means that provides for analog pre-processing and analog to digital conversion will generally comprise an analog pre-processor, an ADC, a digital signal processor (DSP) and a communications/storage device. Analog preprocessing typically involves amplification to rescale signals from low-level sensor or transimpedance amplifier outputs to be on the order of voltage rails for high-resolution conversion at the risk of saturation. Signal-level compression is desirable to provide for a greater dynamic range. In such cases, ADC provides for data transmission, storage and further processing. ADCs assist in converting a "real" analog echoes, which may be non-linear, into digital signals e.g., by compression or compression followed by decompression. Compression increases dynamic range and linearizes many exponential-like functions. Compression followed by decompression, provides the added benefit of increasing signal-to-noise ratio (SNR). Compression is performed in the analog domain using log amplifiers, or alternatively, in the digital domain as part of a digital signal processing (DSP) routine. In one exemplary approach, compressing ADCs are implemented that utilize a successive-approximation technique.

In an alternative embodiment, the ADC circuit includes an isolation circuit, an input circuit including a resistor chain, a plurality of fixed threshold comparators, and an encoder, wherein the resistor chain includes a plurality of resistors connected in series. And the isolation circuit is configured to isolate the device component supplying the analog input signal from the input circuit. The isolation circuit can be connected to the input circuit at an uppermost node of the resistor chain, and wherein 2^N values of the analog input voltage are connected to inputs of the fixed threshold comparators to produce corresponding output signals. In accordance with this embodiment, the analog signal is converted to a digital signal by aw process comprising compressing the analog input signal and converting the compressed analog input signal to a digital signal in a single step.

The ADC may be a standard parallel Flash ADC e.g., including an input buffer, a plurality of comparators, a resistor ladder network, and an encoder. An input signal Vi_n is connected via the input buffer to the non-inverting inputs of 2^N-1 parallel comparators. The inverting inputs of the respective comparators are connected to an equal number of discrete reference voltages generated by the resistive ladder.

Comparators produce a logic "0" or "1" depending on whether the input voltage is lower or higher than the reference voltage. The comparators produce an output of

"thermometer" code (e.g., 0 . . . 01 . . . 1). The output of the comparators are connected to the encoder which produces a binary output depending upon where the " . . . 01 . . . " transition occurs.

In another example, a Flash ADC includes an input buffer configured as a common drain amplifier biased with a current, a resistive ladder having a plurality of resistors, a plurality of fixed threshold comparators, and an encoder. The input buffer is configured to isolate the resistive ladder from an analog input signal. The input buffer is connected to the resistive ladder at an uppermost node of the resistive ladder, and wherein 2^N values of the analog input signal are connected to inputs of the fixed threshold comparators to produce corresponding output signals. The analog input signal is provided via the input buffer in order to provide increased drive current to the resistive ladder to isolate the resistive ladder and minimize loading of a device supplying the analog input signal. Compression of the analog input signal and conversion of the compressed analog input signal to a digital representation are performed in a single step.

Various approaches exist for achieving compression in the signal processing chain, carried out as either analog compression or digital compression. In one example, a logarithmic amplifier is utilized. In another example, integrator and differentiator functionalities, e.g., built from op-amp circuits, are employed.

In another example, a sensor device of the present invention utilizes a signal preprocessing means that comprises a preamplifier connected directly to the ultrasonic receiver and a bandpass filter, and configured to ignore and remove confounding signals, such as rapid albeit weak echoes. As used herein, the term "preamplifier" means an amplifier with bandwidth, noise, and interfacing characteristics that take into account the specifics of the reflected echo, in particular the main reflected echo, and the physical interface. The output of a preamplifier is coupled to the signal pre-processing chain as discussed herein above. In use, an echo is applied to the face of the ultrasonic receiver and the preamplifier is activated. Preferably a recovery period is provided following activation of the ultrasonic receiver and/or preamplifier, during which downstream signal pre-processing is blanked to further reduce remaining artefacts. A feedback mechanism may be activated or turned off or modulated by the frequency range of the echoes received by the ultrasonic receiver, to thereby modulate the functionality of the pre-processing circuit e.g., by modifying electrode charge of the physical interface on the ultrasonic receiver. The feedback mechanism may be continuously adapted to changes in the pre-processing circuit, or made to follow a specific time profile e.g., number of pulses per second.

In another example, a sensor device of the present invention utilizes a signal pre- processing means that comprises a bandpass filter connected directly to a preamplifier or other component of the signal pre-processing means e.g., precision rectifier or envelope follower or ADC, or alternatively connected directly to a preamplifier and one or more computational means including, for example, a sensor processor. Signals from the preamplifier are able to be submitted to the bandpass filter to filter out unwanted acoustic noise i.e., outside the preferred frequency of about 4OkHz and then pre- processed further or submitted to the calculation means.

In another example, a sensor device of the present invention utilizes a signal preprocessing means that comprises a precision rectifier connected directly to another component of the pre-processing circuit such as the bandpass filter or ADC, and an envelope follower. The rectifier, when present in the pre-processing circuit permits the start of the main echo to be determined. In one example, the precision rectifier, when present, is a full wave precision rectifier i.e., a rectifier that transforms negative parts of the sine wave into positive sine waves. In another example, the precision rectifier, when present, is a half wave precision rectifier i.e., a rectifier that ignores negative parts of the sine wave.

In another example, a sensor device of the present invention utilizes a signal preprocessing means that comprises an envelope follower connected directly to another component of the pre-processing circuit such as the bandpass filter or signal rectifier, and an ADC or sensor processor. An "envelope detector" or "envelope follower" is a part of the pre-processing circuit that takes a high-frequency signal as input, and provides an output that is an "envelope" of the original signal wherein a capacitor in the circuit stores charge on the rising edge of the wave and releases the charge slowly through a resistor when the signal falls to thereby smooth the wave and reduce or remove ripples from the signal output. The envelope follower is preferably utilized following half-wave or full-wave rectification of the signal and in conjunction with analog-to-digital conversion of the echo signal.

In one particularly preferred example, the signal pre-processing means comprises a circuit positioned between the ultrasonic receiver and one or more computational means, said circuit comprising a preamplifier, a bandpass filter, a half-wave precision rectifier, an envelope follower and ADC. Preferably, the pre-processing circuit comprises a preamplifier, a bandpass filter, a half-wave precision rectifier, an envelope follower and ADC linked sequentially, i.e., in series, and positioned between the ultrasonic receiver and one or more computational means.

In another particularly preferred example, the signal pre-processing means comprises a circuit positioned between the ultrasonic receiver and one or more computational means, said circuit comprising a preamplifier and a bandpass filter. Preferably, the pre- processing circuit comprises a preamplifier and a bandpass filter linked sequentially, i.e., in series, and positioned between the ultrasonic receiver and one or more computational means.

Computational means The computational means of the sonar device calculates the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes and/or the distance(s) from the transmitter to the plant material from the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes and/or determines one or more plant yield characteristics from said distance(s). Preferably, the computational means performs two of these functions and more preferably all three of these functions. The computational means may also perform other functions e.g., as described herein.

The computational means comprises an algorithm that corrects for the effect of variations in ambient temperature as determined by the temperature sensor.

It will be apparent to the skilled artisan that a variation in vehicle height may return errors in calculated distance(s) from the transmitter to the plant material and thereby lead to erroneous data for one or more plant yield characteristics. To correct for such an error, the computational means also comprises an algorithm that modulates sensor height in response to a variation in compression and/or de-compression of a vehicle suspension. In one example, the computational means receives data pertaining to compression and/or de-compression of a vehicle suspension, determines vehicle height from the data, and adjusts the sensor height up or down e.g., as described herein above, before an ultrasonic pulse is emitted from the ultrasonic transmitter. In another example, the computational means receives data pertaining to vehicle height and adjusts the sensor height up or down e.g., as described herein above, before an ultrasonic pulse is emitted from the ultrasonic transmitter.. In another example, the computational means processes data pertaining to vehicle height and adjusts the sensor height up or down e.g., as described herein above, before an ultrasonic pulse is emitted from the ultrasonic transmitter.

In another example to correct for variation in vehicle height, the computational means comprises an algorithm that corrects for a variation in compression and/or decompression of a vehicle suspension in response to a variation in vehicle height. In one example, the computational means receives data pertaining to compression and/or decompression of a vehicle suspension, determines vehicle height from the data, and calculates distance(s) from the transmitter to the plant material accounting for the variation in vehicle height. In another example, the computational means receives data pertaining to vehicle height and calculates distance(s) from the transmitter to the plant material accounting for the variation in vehicle height. In another example, the computational means processes data pertaining to vehicle height and calculates distance(s) from the transmitter to the plant material accounting for the variation in vehicle height..

It will be apparent to the skilled artisan that a variation in terrain may return errors in calculated distance(s) from the transmitter to the plant material and thereby lead to erroneous data for one or more plant yield characteristics. To correct for such an error, the computational means also comprises an algorithm that modulates sensor height in response to a variation in terrain. In one example, the computational means receives data pertaining to terrain topography, determines a change in sensor height e.g., relative to tared sensor height, from the data, and adjusts the sensor height up or down e.g., as described herein above, before an ultrasonic pulse is emitted from the ultrasonic transmitter. In another example, the computational means receives data pertaining to terrain topography and adjusts the sensor height up or down e.g., as described herein above, before an ultrasonic pulse is emitted from the ultrasonic transmitter. In another example, the computational means processes data pertaining to terrain topography and adjusts the sensor height up or down e.g., as described herein above, before an ultrasonic pulse is emitted from the ultrasonic transmitter.

In another example to correct for variation in terrain, the computational means comprises an algorithm that corrects for a variation in terrain topography e.g., relative to topography of the terrain when the sensor is tared. In one example, the computational means receives data pertaining to terrain topography, determines sensor height from the data e.g., relative to tared sensor height, and calculates distance(s) from the transmitter to the plant material accounting for the variation in sensor height e.g., from tared sensor height. In another example, the computational means processes data pertaining to terrain topography, determines sensor height from the data e.g., relative to tared sensor height, and calculates distance(s) from the transmitter to the plant material accounting for the variation in sensor height e.g., from tared sensor height.

Preferably, the one or more computational means is(are) selected from a central processing unit (CPU) such as, for example a 6-bit, 16-bit, 32-bit, 64-bit, 128-bit or 256-bit CPU, a microcontroller comprising such a CPU, a microprocessor core comprising a plurality of such CPUs, a sensor controller, a system-on-a-chip (SoC), digital signal processor (DSP) or nanoprocessor, preferably having a programmable facility. Combinations and pluralities of such architectures are not excluded. It is well within the art for a single CPU, microcontroller, sensor controller, microprocessor core, SoC, DSP or nanoprocessor to perform all data storage, collection, and computation to provide the requisite yield characteristic(s).

The computations performed by the computational means are based at least in part on the output of the pre-processing circuit and temperature sensor. For example, the output of the pre-processing circuit is interpreted as a unit of time between a pulse of ultrasonic energy and the main echo of that pulse, averaged over several pulses at each position, and the output of the temperature sensor i.e., ambient temperature, is interpreted to indicate corrections that are required to the calculated unit of time at that temperature, in view of the variable speed of time at different temperatures. For example, the effect of variations in ambient temperature as determined by the temperature sensor can be corrected as described herein.

Sensor driver

Exemplary sensor drivers include a 10V-36V driver device.

Control processes

It will also be apparent from the preceding description that the device of the present invention may be controlled by a central processing unit (CPU), microprocessor or sensor processor. The CPU, microprocessor or sensor processor also controls the operation of the various components of the device (e.g., ultrasonic transmitter, ADC, pre-processing feedback, etc) and interfaces with the display, which may be either a keypad or touch-screen with LCD and backlighting.

In a preferred example, the CPU or sensor processor communicates with a host computer, such as, for example, a laptop, PDA, mobile or cellular telephone device, via wireless Ethernet to transfer data there between.

Reduction of interference Preferably, the ultrasonic receiver is adjustably recessable within a sensor head relative to the ultrasonic transmitter to thereby restrict the cone width of the echoes received. The distance by which the ultrasonic receiver is recessed may vary, the only consideration being that it is recessed a sufficient distance to reduce or prevent interference from structures such as wheels of the vehicle to which it is mounted in use that would otherwise produce unwanted echoes from the transmitted pulses of ultrasonic energy. For example, the transmitted pulses may produce a wide cone having an angle of about 40 degrees, effectively swamping the area below the sensor head including moving vehicle parts and, if the angle of the ultrasonic receiver is not restricted to be less, than the angle of transmitted pulses, unwanted echoes arising e.g., from vehicle components will be included in the received signals. By recessing the ultrasonic receiver, such unwanted echoes can be eliminated such that only echoes arising from the plant material are received.

Without being bound by any theory or mode of action, recessing of the ultrasonic receiver within a sensor head to thereby restrict the cone width of the echoes received also permits primary echoes received from the crop to the walls of the recess to be reflected onto the receiving face of the ultrasonic receiver, thereby amplifying signal strength and reducing variability dur to different crop density.

As an alternative to recessing the ultrasonic receiver, the ultrasonic transmitter can be adjustably recessable within a sensor head to thereby restrict the cone width of the timed pulses of ultrasonic energy. This also reduces or prevents interference from structures such as wheels of the vehicle to which it is mounted in use that would otherwise produce unwanted echoes from the transmitted pulses of ultrasonic energy. For example, by restricting the cone width of transmitted pulses to less than about 40 degrees, the transmitted pulses are directly more accurately towards the crop and avoiding vehicle parts, as opposed to swamping the area below a sensor head. Because the signals are directed exclusively to the crop, no unwanted echoes can be produced by reflection of the transmitted signal from other elements.

Standard means for adjusting the distance by which the ultrasonic receiver or ultrasonic transmitter is recessed may be employed e.g., the ultrasonic receiver or ultrasonic transmitter to be recessed can be fitted with a male screw thread portion for adjustment by rotation within a female threaded portion of a sensor head. Alternatively, the ultrasonic receiver or ultrasonic transmitter to be recessed can be fitted with ridges that are positioned within the sensor head by a click lock mechanism.

Global positioning System (GPS)

In a further example, the device further comprises a global positioning system (GPS) i.e., a radio navigation system that permits a user to determine their exact location within a paddock or field and to thereby determine and/or display yield characteristics for the precise paddock or field position e.g., relative to other paddocks or fields or other paddock or field positions, and/or over a specified period of time. In a preferred form, the device provides elevation data in addition to longitude and latitude coordinates. For example, a precise determination of a terrain location in two or three dimensions can be calculated and stored so that the location data includes information to identify yield characteristic data at that location e.g., in two or three dimensions. Preferably, three-dimensional location data are mapped to two dimensions and stored as Cartesian coordinates (x_ls yi, Z₁, etc.) relative to the location of the vehicle (defined as X₀, yo, Zo, etc) and, by storing only the x- and y-coordinates and not involving the z- coordinates in computations, memory is conserved and mathematical processing requirements are reduced. Co-ordinate systems other than Cartesian (e.g., polar or spherical) may be used.

In a further example, a 2-dimensional image can be constructed along a single vertical or horizontal slice. Alternatively, 3-dimensional images can be constructed through a series of 2 dimensional ultrasonic pulses directed to the plant material wherein the direction of 2 dimensional strips is perpendicular to the track of the vehicle. Imaging means

In a further preferred example, the device further comprises imaging means to transform data into a 2-dimension or 3 -dimensional representation of the paddock or field profile and display the representation. ■

Calculation of yield characteristic data

To determine the main reflected echoes, echo signals are pre-processed by a preprocessing means e.g., comprising a circuit positioned between the ultrasonic receiver and the computational means e.g., a microcontroller, microprocessor or nanoprocessor, said circuit preferably comprising a preamplifier, a 40 kHz bandpass filter, a half-wave precision rectifier, an envelope follower and ADC in series. The processed signal is digitised by the ADC and transmitted to the computational means. A temperature sensor records ambient temperature and transmits temperature data to the computational means for determination of the speed of sound at that temperature. The computational means at least comprises sufficient programming logic for calculating distance from the sensor head to the plant material from the digitized data on the average temperature-corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes. The point where the differential of the sine wave exceeds a user-defined trigger point i.e., the rate of change in the sine wave exceeds this threshold trigger point value, indicate the start position of the main reflected echo, as shown in Figure 8. This start point for the main echo serves as the basis for calculating the distance from the sensor head to the plant material as a function of the temperature-corrected speed of sound at ambient temperature and the distance from the sensor head to the ground as determined from a tare reading, as explained, for example, in the legend to Figure 5.

The corrected unit of time between a pulse of ultrasonic energy and the main echo of that pulse, averaged over several pulses at each position is transformed to provide a distance between the sensor head and the plant material, which, when the distance from the sensor head to the ground is known e.g., by prior taring of the device or prior knowledge of the terrain, permits calculation of the height of the crop at a particular location. Based on calibration equations for yield characteristic data of different crop plant species and different combinations of crop plant species, crop height data are transformed by the calculating means to other yield characteristic data. For example, correlations between crop height and dry matter yield per unit area permit statistically significant transformation of height data into dry matter yield data. Yield characteristic data are stored in at least one memory of the calculating means.

Arrangement of components No strict compliance with the arrangement of components in a sensor head and/or interface boxes is required. A sensor head box will generally comprise a sensor driver, ultrasonic transmitter, ultrasonic receiver, and optionally one or more other components such as temperature sensor and signal pre-processing means. An interface box will generally comprise one or more computational means, means for entering data and means for displaying data and optionally, temperature sensor. An interface box may also comprise a touch screen pad or key pad for data entry and data field selection, and may comprise an LCD display for viewing data entered into the device or produced by the device.

A sensor driver is generally connected to the ultrasonic transmitter. A microcontroller or sensor microprocessor (which may be located in the sensor head box or the interface box), is also generally connected electrically or by wireless means to the sensor driver and controls the timed pulses of ultrasonic energy produced by the ultrasonic transmitter. A temperature sensor is also connected to a port of the microcontroller or sensor microprocessor, and these components may be located together in a sensor head box or interface box, or positioned separately in a sensor head box and interface box. A signal pre-processing means is generally connected to an ultrasonic receiver to permit filtering and modifications to the received echo signals. The filtered echo information is generally passed to an analog-to-digital converter (ADC), if present, by wired or wireless connection, and then to a microcontroller or sensor microprocessor by wired electrical or wireless means. Alternatively, if no ADC is present, the filtered echo information is passed directly to a microcontroller or sensor microprocessor (which may be located in the sensor head box or the interface box) for calculations of yield characteristic data to be made.

In accordance with the examples hereof, an ultrasonic transmitter and ultrasonic receiver are conveniently positioned in a single sensor head box mountable on a vehicle travelling over the surface of the plant material such that the transmitted timed pulses of ultrasonic energy are capable of being directed towards plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants. Vehicle to which the device is mountable

The term "vehicle" as used in the present context shall be construed in its broadest possible context to include powered vehicles such as tractors, motor bikes, trucks, etc., non-powered vehicles such as bicycles and other pedal-driven vehicles, and any trailors, trolleys, sledges or other wheeled frames that are attached to and driven by powered or non-powered vehicles.

A sensor head box can be mounted on the front, rear or sides of a vehicle, preferably such that the transmitted timed pulses of ultrasonic energy are capable of being directed towards plant material without interference from vehicle components e.g., turning wheels. As exemplified herein, a sensor head box is mounted on the front of a vehicle such as attached to a front bull bar or bumper.

An interface box is conveniently mounted on a vehicle such that it is in view of the operator of the vehicle e.g., on the dashboard or console.

Use of the sonar device

The present invention also provides for the use of a sonar device of the present invention as described according to any example hereof in the determination of one or more plant yield characteristics, e.g., plant height or dry matter weight per unit area.

The present invention also provides for the use of a sonar device of the present invention as described according to any embodiment or example hereof in the determination of one or more plant yield characteristics with reference to a location within a paddock or field.

The present invention also provides for the use of a sonar device of the present invention as described according to any embodiment or example hereof in the determination of one or more plant yield characteristics with reference to a specified period of time.

The present invention also provides for the use of a sonar device of the present invention as described according to any embodiment or example hereof in the determination of one or more plant yield characteristics with reference to a location within a paddock or field and with reference to a specified period of time. The present invention also provides a method for determining one or more plant yield characteristics. In one example, the method comprises: a) transmitting one or more pulses of ultrasonic energy towards the plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) receiving reflected echoes of the transmitted timed pulses from the plant material; c) determining ambient temperature; d) determining reflected main echoes of the transmitted timed pulses from the plant material; and e) calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes wherein said time is corrected for the effect of variations in ambient temperature as determined at (c); f) calculating the distance(s) from the transmitter to the plant material from the corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes; and g) determining one or more plant yield characteristics from said distance(s).

In a second example, the present invention also provides a method for determining one or more plant yield characteristics comprising: a) transmitting one or more pulses of ultrasonic energy towards the plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) receiving reflected echoes of the transmitted timed pulses from the plant material; c) determining ambient temperature; d) determining reflected main echoes of the transmitted timed pulses from the plant material; and e) calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes wherein said time is corrected for the effect of variations in ambient temperature as determined at (c); f) calculating the distance(s) from the transmitter to the plant material from the corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes; g) entering data in relation to the plant material; and h) determining one or more plant yield characteristics from said distance(s). As used herein, the term "data in relation to the plant material" shall be construed broadly to mean any and all data obtainable on the source of plant material, agricultural or agronomic methods employed in growing the plant material e.g., sowing density, fertilization and watering regime, grazing intensity, harvest data, height-to-dry matter correlations, dry weight-to-fresh weight ratios, plant compositional data and nutrient data, and data on seasonal variations in any of said data. Terrain information and specific location data are also able to entered. Data that are not calculable directly or indirectly from temperature-corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes, such as plant source, sowing density, fertilization regime, watering regime, plant compositional data, etc. may be entered at any time in the process. On the other hand, data that are required for calculation of one or more yield characteristics derivable from the temperature- corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes, such as height-to-dry matter correlations with or without seasonal variation data, are entered at any time before one or more plant yield characteristics is determined from the distance(s).

In a third example, the present invention also provides a method for determining one or more plant yield characteristics comprising: a) transmitting one or more pulses of ultrasonic energy towards the plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) receiving reflected echoes of the transmitted timed pulses from the plant material; c) determining ambient temperature; d) determining reflected main echoes of the transmitted timed pulses from the plant material; and e) calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes wherein said time is corrected for the effect of variations in ambient temperature as determined at (c); f) calculating the distance(s) from the transmitter to the plant material from the corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes; g) determining one or more plant yield characteristics from said distance(s); and h) displaying data in relation to the distance(s) and/or one or more plant yield characteristics.

As will be apparent form the preceding description, data are generally displayed using a convention LED screen display. Such display may be on-site or at a remote location from the site where the measurements were taken e.g., on a laptop, PDA, mobile or cellular telephone device.

In a fourth example, the present invention also provides a method for determining one or more plant yield characteristics comprising: a) transmitting one or more pulses of ultrasonic energy towards the plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) receiving reflected echoes of the transmitted timed pulses from the plant material; c) determining ambient temperature; d) determining reflected main echoes of the transmitted timed pulses from the plant material; and e) calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes wherein said time is corrected for the effect of variations in ambient temperature as determined at (c); f) calculating the distance(s) from the transmitter to the plant material from the corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes; g) entering data in relation to the plant material; h) determining one or more plant yield characteristics from said distance(s); and i) displaying data in relation to the distance(s) and/or one or more plant yield characteristics.

In still further examples of the foregoing method, it is preferred to provide a sonar device of the present invention as described according to any embodiment or example hereof, optionally with instructions as to use of the device in the determination of one or more plant yield characteristics, e.g., plant height or dry matter weight per unit area. Optionally, such instructions comprise instructions as to use of the device in the determination of one or more plant yield characteristics with reference to a location within a paddock or field and/or with reference to a specified period of time. In each of the preceding embodiments, it is preferred to calculate the average height of the plant material from the average corrected times between the transmission of each pulse of ultrasonic energy and its reception.

Plants and Plant yield characteristics

As used herein, the term "plant yield characteristic" shall be taken in its broadest context to include any measurable physical plant characteristic that contributes to or is determinative of yield, such as, for example, plant height; fresh or dry matter weight per unit area e.g., hectare, acre, etc. of biomass, shoot, leaf, seed or head; and fresh or dry matter weight per grazing animal of fodder material. By "fodder material" is meant that part of a pasture crop that a grazing animal would normally graze upon i.e., ingest. In one example, the plant yield characteristic is plant height. In another example, the plant yield characteristic is dry matter weight per unit area e.g., hectare, acre, etc. of biomass, shoot, leaf, seed or head, and preferably dry matter weight per unit area e.g., hectare, acre, etc. of leaf material. In another example, the plant yield characteristic is dry matter weight per grazing animal of fodder material.

In one example, the plant for which a plant yield characteristic is determined is a crop plant, such as, for example, a food crop plant (e.g., a grain crop plant such as maize, wheat, rice, rye, millet, sorghum, barley, quinoa, sugarcane, etc., or a vegetable such as sugar beet, chicory, etc., or a fruit bearing plant such as tomato, apple, orange, mandarin or other citrus), an oilseed crop plant (e.g., canola, rapeseed, jojoba, meadow foam, flax, soybean, sunflower, cotton, corn, olive, safflower, cocoa and peanut), a pasture crop plant (e.g., a grass such as a perennial grass or annual grass or bunchgrass, including but not limited to, bent grass, fescue, ryegrass, weeping grass, orchard grass, brome grass, canary, grass, lucerne, kikuyu, paspalum, prairie grass, gamba grass,

Surinam grass, buffel grass, Rhodes grass, bermuda grass, pangola grass, weeping love grass, jaragua, molasses grass, guinea grass, napier grass, setaria grass and mixtures thereof), or other harvestable crop plant.

In another example, the plant is a pasture crop plant, such as a grass selected from the group consisting of clover, lucerne, kikuyu, paspalum, prairie grass and mixtures thereof. EXAMPLE 1

A sonic device and use thereof according to the drawings

The present invention is now described with reference to the accompanying drawings wherein the sonic device of the present invention generally comprises two parts connected either with a wire, or alternatively, by wireless means using known network protocols and devices, and mounted on an all-terrain vehicle for determination of one or more crop yield characteristics while the vehicle is in motion.

The first part of the device generally consists of an interface box (2) mounted in a position accessible to the driver of the vehicle as shown in Figure 1. As illustrated in Figure 2, the interface box (2) generally comprises a display (6) for visual feedback to the operator, and a keypad (8) for data entry. In a variation of this feature shown in Figure 10, the display can comprise a touch-screen with backlighting showing several windows for data entry, collection and storage.

The interface box (2) can include one or more computational means such as, for example, in the form of at least one microcontroller (32) or microprocessor (34) for calculating: (i) the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes; (ii) the distance(s) from the transmitter to the plant material from the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes; and (iii) one or more plant yield characteristics from said distance(s), wherein said computational means comprises an algorithm that corrects for the effect of variations in ambient temperature as determined by a temperature sensor (30) positioned within the interface box (2) or external to it. The computational means can comprise other known integers e.g., one or more microprocessors, nanoprocessors, etc. In addition to performing calculations, the computational means also controls various elements of the sonar device of the present invention, e.g., ultrasonic transmitter, ADC, pre-processing feedback, etc., and interfaces with the display, which may be either a key pad or touch- screen with backlighting.

The second part of the device is a sensor head box (4) comprising an ultrasonic transmitter (10) connected for example to a 10V or 36V driver (12), which in turn is connected by a wired or wireless link (14) to one or more computational means such as in the form of at least one microcontroller (32) or microprocessor (34). In one configuration, the one or more computational means such as in the form of at least one microcontroller (32) or microprocessor (34) is also positioned within the sensor head box (4). In another configuration, the one or more computational means such as in the form of at least one microcontroller (32) or microprocessor (34) is positioned within the interface box (2). The sensor head box (4) also comprises an ultrasonic receiver (16) positioned in close proximity to the ultrasonic transmitter (10) and preferably recessed within the sensor head box a sufficient distance to thereby restrict the cone width of the echo sensed by the ultrasonic receiver and exclude unwanted echoes such as those generated by moving vehicle parts. The ultrasonic receiver is generally connected to pre-processing means comprising, for example, a bandpass filter (22), preamplifier (18), analog-to-digital converter (ADC) (28), a half-wave or full-wave precision rectifier (24), and an envelope follower (26), connected as exemplified in Figure 2 and/or Figure 4. A temperature sensor (30) may also be connected to the ADC (28) or directly to the computational means e.g., a microcontroller (32) or microprocessor (34). The ADC (28) is generally connected to the computational means e.g., a microcontroller (32) or microprocessor (34) through a wired or wireless data link.

On a signal from the computational means e.g., microcontroller (32) or microprocessor (34), the ultrasonic transmitter (10) transmits one or more short pulses of ultrasonic energy with frequency centred on about 40 kHz i.e., beyond the range of human hearing. As illustrated in Figure 1 and Figure 2, the sensor head box (4) is angled so that one side of the box faces the plant material at an angle up to about 20 degrees relative to the longitudinal axis of the plant stems, and preferably in the range of about 10 degrees to about 15 degrees relative to the longitudinal axis of the plant stems. The sound is reflected by any plant material (e.g. grass) and the echo is received by the ultrasonic receiver (16). The signal is then subjected to signal pre-processing means, comprising amplification using a preamplifier (18) to generate a preamplified signal (40). In this preferred embodiment of the present invention, the preamplifier (18) has a gain of 100. The preamplified signal (40) has a signal-to-noise ratio much greater than that generated by the ultrasonic receiver (16). This preamplified signal (40) is i 1 lustrated in Figure 3.

The ultrasonic energy in the echo is filtered to ensure that only echoes having frequencies matching or near the frequencies of the transmitted sound (e.g., centred around 40 kHz) are retained. Accordingly, the amplified signal (40) is passed through a bandpass filter (22) centred on 4OkHz to create a bandpassed signal (42). The bandpass filter (22) thus filters out unwanted acoustic noise from the transducer. The bandpass filter (22) can also attenuate any small, fast transient spikes in the signal, and avoids false echo detection from noise and exceptionally tail blades of grass or pasture.

The bandpassed signal (42) is passed through a full-wave rectifier that transforms negative parts of the sine wave into positive sine waves, or more preferably, a half wave precision rectifier (24) that ignores negative parts of the sine wave. The rectified signal (44) is passed through an envelope follower (26) to create an envelope signal

(46). This envelope signal (46) is fed into the ADC (28), which samples the envelope signal (46) and converts the analog signal into a digital signal. The digitized signals for the sample data are passed to the computational means e.g., microcontroller (32) or microprocessor (34) through the wired or wireless data link (14).

In the preferred embodiment the ADC (28) samples the envelope signal (46) at a rate of about 50khz. Sampling is for a period of milliseconds from the time of transmission of each pulse of ultrasonic energy from the ultrasonic transmitter (10). The sampled data are stored in a memory by the computational means e.g., microcontroller (32) or microprocessor (34). A representation of the sampled data (50) is shown in Figure 8. The sampled data (50) are processed by the computational means e.g., microcontroller (32) or microprocessor (34) to determine the main reflected echo in the samples that represents the start of the main echo of ultrasonic energy that has reflected off the crop plant material. The computational means e.g., microcontroller (32) or microprocessor (34) determines the sample that represents the start of the reflected pulse by identifying the sample that corresponds to the highest rate of change of the received ultrasonic energy. This is done by calculating the first derivative of the sampled data for each set of samples e.g., each set of five or ten samples. The maximum value of the calculated first derivative corresponds to the set of samples during which the rate of change of the received ultrasonic energy is greatest. The mid-sample of this set of samples is selected as the sample that represents the start of the reflected pulse. A graph (54) representing the first derivative of the sampled data is shown in Figure 8.

In this way, the computational means e.g., microcontroller (32) or microprocessor (34) calculates the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes. Once this is determined, the computational means e.g., microcontroller (32) or microprocessor (34) calculates the distance from the sensor head (4) to the top of the grass at that point may be calculated from the following formula: Start sample x time between samples x 0.33131 x VfI + Temp (degrees Q/273.16) Dist = 2 wherein: "Start Sample" is the time for the main reflected echo to be received by the ultrasonic receiver (16); and "Time between samples" is the time between each transmitted pulse.

The ambient temperature in Celsius is available to the computational means e.g., microcontroller (32) or microprocessor (34) through the temperature sensor (30). the output of which is also sampled by the ADC (28) or directly by the computational means.

In use, the apparatus is affixed to a vehicle such as an all terrain vehicle illustrated in Figure 1. Before measurement takes place, the apparatus is activated in a "tare" mode when directed to ground on which there is no grass e..g., a strip of freshly-mowed pasture. This enables the computational means e.g., microcontroller (32) or microprocessor (34) to calculate and store the value of the distance from the sensor head (4) to the ground. Taring is generally conducted each time measurements are required of a field or paddock that has not been tared previously, and when the height of the vehicle is varied e.g., by virtue of carrying a different load to that carried during previous tare operations, and when a different vehicle is employed. Taring is also recommended when the terrain is modified significantly e.g., by potholing, rain, landslide, etc.

Once tared, the sonar device may be activated in measuring mode, and the vehicle then driven across the crop. As the sensor head (4) is attached to the vehicle, it travels in a plane substantially parallel to the ground and the distances between the ultrasonic transmitter (10) and the ground and between the ultrasonic receiver (16) and the ground are substantially the same. Periodically (typically many times a second) the distance from the sensor head (4) to the top of the grass is measured as described above. These measured distances are averaged and then subtracted from the previously measured distance from the sensor head to the ground to determine the average height of the crop. Yield characteristic data are calculated by the computational means from the crop height data as described herein above. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps,

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia or elsewhere before the priority date of each claim of this application.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. For example, the sampling period may be adjusted or different signal processing techniques used. The sensor head and the interface box may be mounted in the same housing, or may have components distributed around a vehicle. The present embodiment is, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

WE CLAIM:

1. A sonar device for determining one or more plant yield characteristics, wherein the device comprises: a) an ultrasonic transmitter for transmitting timed pulses of ultrasonic energy towards plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) an ultrasonic receiver for receiving reflected echoes of the transmitted timed pulses from the plant material; c) a temperature sensor; d) a signal pre-processing means for determining reflected main echoes of the transmitted timed pulses from the plant material; and e) one or more computational means for calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes, the distance(s) from the transmitter to the plant material from the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes and for determining one or more plant yield characteristics from said distance(s), wherein said computational means comprises an algorithm that corrects for the effect of variations in ambient temperature as determined by the temperature sensor; and wherein the device is mountable on a vehicle travelling above the surface of the plant material.

2. The sonar device of claim 1 further comprising means for entering data in relation to the plant material.

3. The sonar device according to claim 2, wherein the means for entering data in relation to the plant material comprises a touch screen pad or key pad.

4. The sonar device according to any one of claims 1 to 3 further comprising means for displaying data in relation to the plant material and/or distance(s) and/or one or more plant yield characteristics.

5. The sonar device according to claim 4, wherein the means for displaying data in relation to the plant material and/or distance(s) and/or one or more plant yield characteristics comprises an LCD display.

6. The sonar device according to any one of claims 1 to 5, further comprising a sensor driver.

7. The sonar device according to claim 6, wherein the sensor driver is a 10V or a 36V driver device.

8. The sonar device according to any one of claims 1 to 7 further comprising a microcontroller or sensor microprocessor that controls the timed pulses of ultrasonic energy produced by the ultrasonic transmitter.

9. The sonar device according to any one of claims 1 to 8 further comprising an analog-to-digital converter (ADC).

10. The sonar device according to any one of claims 1 to 9 further comprising a global positioning system (GPS) for receiving and/or processing and/or displaying data pertaining to the location of plant material.

11. The sonar device according to any one of claims 1 to 10 further comprising an imaging means for transforming data into a 2-dimensional or 3 -dimensional representation and displaying the representation.

12. The sonar device according to any one of claims 1 to 11, wherein the ultrasonic transmitter transmits pulses of ultrasonic energy having a frequency above about 20 kHz.

13. The sonar device according to any one of claims 1 to 12, wherein the ultrasonic receiver is configured to receive echoes above about 20 kHz.

14. The sonar device according to any one of claims 1 to 13, wherein the temperature sensor comprises a thermistor or thermocouple.

15. The sonar device according to any one of claims 1 to 14, wherein the signal preprocessing means comprises one or more components selected from the group consisting of a preamplifier, a bandpass filter, a precision rectifier, an envelope follower and an analog-to-digital converter (ADC).

16. The sonar device according to claim 15, wherein the signal pre-processing means comprises an ADC.

17. The sonar device according to claim 16, wherein the signal pre-processing means comprises an ADC, an analog pre-processor, digital signal processor (DSP) and a communications or storage device.

18. The sonar device according to claim 9 or any one of claims 15 to 17, wherein the ADC is a Flash ADC.

19. The sonar device according to claim 15, wherein the signal pre-processing means comprises a preamplifier.

20. The sonar device according to claim 15, wherein the signal pre-processing means comprises a bandpass filter.

21. The sonar device according to claim 15, wherein the signal pre-processing means comprises a precision rectifier.

22. The sonar device according to claim 16, wherein the precision rectifier is a half- wave precision rectifier.

23. The sonar device according to claim 15, wherein the signal pre-processing means comprises an envelope follower.

24. The sonar device according to any one of claims 1 to 23, wherein the signal preprocessing means comprises a preamplifier and a bandpass filter.

25. The sonar device according to any one of claims 1 to 24, wherein the signal pre- processing means comprises a preamplifier, a bandpass filter, a precision rectifier, an envelope follower and an analog-to-digital converter (ADC).

26. The sonar device according to any one of claims 1 to 25, wherein the one or more computational means comprise(s) a central processing unit (CPU).

27. The sonar device according to any one of claims 1 to 25, wherein the one or more computational means comprise(s) a microprocessor core comprising a plurality of central processing units (CPUs).

5 28. The sonar device according to any one of claims 1 to 25, wherein the one or more computational means comprise(s) a microcontroller comprising a central processing unit (CPU).

29. sonar device according to any one of claims 26 to 28, wherein the CPU is a 6- 10 bit, 16-bit, 32-bit, 64-bit, 128-bit or 256-bit CPU.

30. The sonar device according to any one of claims 1 to 25, wherein the one or more computational means comprise(s) a sensor controller.

15 31. The sonar device according to any one of claims 1 to 25, wherein the one or more computational means comprise(s) a system-on-a-chip (SoC).

32. The sonar device according to any one of claims 1 to 25, wherein the one or more computational means comprise(s) a digital signal processor (DSP). 0

33. The sonar device according to any one of claims 1 to 25, wherein the one or more computational means comprise(s) a nanoprocessor.

34. The sonar device according to any one of claims 1 to 33, wherein the one or 5 more computational means has a programmable facility.

35. The sonar device according to any one of claims 1 to 34, wherein the components of said sonar device are provided in two units or boxes and wherein one or more components of one of said units or boxes is(are) in communication with one or 0 more components of the other of said units or boxes by means of a communications cable, data cable or wireless means.

36. The sonar device of claim 35, wherein the components of said sonar device are provided in a sensor head box and an interface box and wherein one or more 5 components of said sensor head box is(are) in communication with one or more components of said interface box by means of a communications cable, data cable or wireless means.

37. The sonar device of claim 36, wherein the sensor head box and/or interface box 5 is/are constructed of water-resistant or moisture-resistant material.

38. The sonar device of claim 36 or 37, wherein the sensor head box comprises the ultrasonic transmitter and ultrasonic receiver.

10 39. The sonar device according to any one of claims 36 to 38, wherein the sensor head box comprises the temperature sensor.

40. The sonar device according to any one of claims 36 to 39, wherein the sensor head box comprises the signal pre-processing means.

15

41. The sonar device according to any one of claims 36 to 40, wherein the sensor head box comprises the sensor driver.

42. The sonar device according to any one of claims 36 to 41, wherein the sensor 0 head box comprises the microcontroller or microprocessor for controlling timed pulses of ultrasonic energy produced by the ultrasonic transmitter.

43. The sonar device according to any one of claims 36 to 42, wherein the sensor head box comprises the analog-to-digital converter (ADC). 5

44. The sonar device of claim 36 or 37, wherein the interface box comprises the one or more computational means.

45. The sonar device according to any one of claims 36, 37 or 44, wherein the 0 interface box comprises the means for entering data.

46. The sonar device according to any one of claims 36, 37, 44 or 45, wherein the interface box comprises the means for displaying data.

47. The sonar device according to claim 36 or 37 or any one of claims 44 to 46, wherein the interface box comprises the microcontroller or microprocessor for controlling timed pulses of ultrasonic energy produced by the ultrasonic transmitter.

48. The sonar device according to claim 36 or 37 or any one of claims 44 to 46, wherein the interface box comprises the temperature sensor.

49. The sonar device according to claim 38, wherein the ultrasonic transmitter is mounted at an angle within the sensor head box sufficient to provide an angle of transmitted waves of up to about 20 degrees relative to the longitudinal shoot axis of plants.

50. The sonar device of claim 49, wherein the end face of the sensor head box is bevelled so as to provide an angle of transmitted waves of up to about 20 degrees relative to the longitudinal shoot axis of plants when the face of the ultrasonic transmitter is in the same plane as the bevelled end face of the sensor head.

51. The sonar device according to any one of claims 38, 49 or 50, wherein the ultrasonic transmitter is recessed within the sensor head.

52. The sonar device according to claim 54, wherein the ultrasonic transmitter is adjustably recessed within the sensor head to thereby restrict the cone width of the timed pulses of ultrasonic energy.

53. The sonar device according to any one of claims 1 to 52, wherein the ultrasonic receiver is directed to the plant material at about the same angle as the ultrasonic transmitter.

54. The sonar device according to any one of claims 1 to 53, wherein the ultrasonic receiver is in the same plane as the ultrasonic transmitter.

55. The sonar device according to any one of claims 1 to 53, wherein the ultrasonic receiver is in a different plane to the ultrasonic transmitter.

56. The sonar device according to claim 55, wherein the ultrasonic receiver is adjustably recessed within the sensor head relative to the ultrasonic transmitter to thereby restrict the cone width of the echoes received.

57. The sonar device of claim 56, wherein the ultrasonic receiver is recessed a sufficient distance to reduce or prevent interference from structures of a vehicle to which it is mounted.

58. The sonar device according to any one of claims 1 to 57, wherein pulses of ultrasonic energy are at predetermined regular intervals.

59. The sonar device of claim 58, wherein a predetermined regular interval is predetermined with respect to a condition selected from crop species, density, variability in crop cover, and climatic condition.

60. The sonar device of claim 58 or 59, wherein a predetermined regular interval is less than about one minute.

61. The sonar device to any one of claims 1 to 60, wherein timed pulses of ultrasonic energy are less than about 20 pulses per second.

62. The sonar device according to any one of claims 1 to 61, wherein a plant yield characteristic is selected from plant height and dry matter weight per unit area.

63. The sonar device according to any one of claims 1 to 62, wherein said device is mounted on a vehicle travelling above the surface of the plant material and wherein the vehicle is a powered vehicle selected from the group consisting of a tractor, motor bike, and truck.

64. The sonar device according to any one of claims 1 to 62, wherein said device is mounted on a vehicle travelling above the surface of the plant material and wherein the vehicle is a bicycle or other pedal-driven vehicle.

65. The sonar device according to any one of claims 1 to 62, wherein said device is mounted on a trailor, trolley, sledge or wheeled frame that is attached to and driven by powered or non-powered vehicle.

66. The sonar device according to any one of claims 63 to 65, wherein said device comprises a sensor head box mounted on the front, rear or sides of a vehicle such that the transmitted timed pulses of ultrasonic energy are capable of being directed towards plant material without interference from vehicle components.

67. The sonar device according to any one of claims 63 to 65, wherein said device comprises an interface box mounted on a vehicle such that it is in view of the operator of the vehicle.

68. Use of a sonar device according to any one of claims 1 to 67 in the determination of one or more plant yield characteristics.

69. The use according to claim 68, wherein the plant yield characteristic is plant height or dry matter weight per unit area.

70. The use according to claim 68 or 69, wherein the one or more plant yield characteristics is determined with reference to location of plant material.

71. The use according to any one of claims 68 to 70, wherein the one or more plant yield characteristics is determined with reference to a specified period of time.

72. A method for determining one or more plant yield characteristics comprising: a) transmitting one or more pulses of ultrasonic energy towards the plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) receiving reflected echoes of the transmitted timed pulses from the plant material; c) determining ambient temperature; d) determining reflected main echoes of the transmitted timed pulses from the plant material; e) calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes wherein said time is corrected for the effect of variations in ambient temperature as determined at (c); f) calculating the distance(s) from the transmitter to the plant material from the corrected time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes; and g) determining one or more plant yield characteristics from said distance(s).

73. The method of claim 72 further comprising displaying data in relation to the distance(s) and/or one or more plant yield characteristics.

74. The method of claim 72 or 73 further comprising entering data in relation to the plant material.

75. A process for determining one or more plant yield characteristics comprising: i) providing a sonar device according to any one of claims 1 to 67; and ii) determining one or more plant yield characteristics by employing said sonar device in a method comprising: a) transmitting one or more pulses of ultrasonic energy towards the plant material at an angle up to about 20 degrees relative to the longitudinal shoot axis of plants; b) receiving reflected echoes of the transmitted timed pulses from the plant material; c) determining ambient temperature; d) determining reflected main echoes of the transmitted timed pulses from the plant material; e) calculating the time between the transmission of the timed pulses of ultrasonic energy and reception of the reflected main echoes wherein said time is corrected for the effect of variations in ambient temperature as determined at

76. The process of claim 75 further comprising displaying data in relation to the distance(s) and/or one or more plant yield characteristics.

77. The process of claim 75 or 76 further comprising entering data in relation to the plant material.

78. The process according to any one of claims 75 to 77 comprising providing the sonar device with instructions as to use of said device in the determination of the one or more plant yield characteristics.

79. The method of claim 74 or the process of claim 77, wherein data in relation to the plant material are selected from sowing density, fertilization regime, watering regime, grazing intensity, harvest data, height-to-dry matter correlation, dry weight-to- fresh weight ratio, plant source, plant species, plant compositional data, nutrient data, seasonal variation data, terrain data and location data.

80. The method according to any one of claims 72 to 74 or the process according to any one of claims 75 to 78 comprising determining the one or more plant yield characteristics with reference to location of plant material.

81. The method according to any one of claims 72 to 74 or the process according to any one of claims 75 to 78 comprising determining the one or more plant yield characteristics with reference to a specified period of time.

82. The method according to any one of claims 72 to 74 or the process according to any one of claims 75 to 78, wherein the plant yield characteristic is plant height or dry matter weight per unit area.

83. The method according to any one of claims 72 to 74 or the process according to any one of claims 75 to 78, wherein the plant for which a plant yield characteristic is determined is a crop plant.

84. The method or process according to claim 83 wherein the crop plant is a food crop plant, an oilseed crop plant or a pasture crop plant.

85. The method or process according to claim 84, wherein the food crop plant is a grain crop plant, a vegetable or a fruit-bearing plant.

86. The method or process according to claim 85, wherein the grain crop plant is selected from maize, wheat, rice, rye, millet, sorghum, barley, quinoa and sugarcane.

87. The method or process according to claim 85, wherein the vegetable is selected 5 from sugar beet and chicory.

88. The method or process according to claim 85, wherein the fruit-bearing plant is selected from tomato, apple, orange, mandarin and other citrus.

10 89. The method or process according to claim 84, wherein the oilseed crop plant is selected from canola, rapeseed, jojoba, meadow foam, flax, soybean, sunflower, cotton, corn, olive, safflower, cocoa and peanut.

90. The method or process according to claim 84, wherein the pasture crop plant is a 15 grass plant.

91. The method or process according to claim 90, wherein the grass plant is selected from a perennial grass, annual grass or bunchgrass plant. 0

92. The method or process according to claim 90, wherein the grass plant is selected from bent grass, fescue, ryegrass, weeping grass, orchard grass, brome grass, canary grass, lucerne, kikuyu, paspalum, prairie grass, gamba grass, Surinam grass, buffel grass, Rhodes grass, bermuda grass, pangola grass, weeping love grass, jaragua, molasses grass, guinea grass, napier grass, setaria grass and mixtures thereof. 5

93. The method or process according to claim 84, wherein the pasture crop plant is selected from the group consisting of clover, lucerne, kikuyu, paspalum, prairie grass and mixtures thereof. 0

94. The sonar device according to any one of claims 1 to 67 further comprising means for correcting for a variation in vehicle height.

95. The sonar device of claim 94, wherein said means comprises computational means. 5

96. The sonar device of claim 95, wherein the computational means comprises an algorithm that modulates sensor height in response to a variation in compression and/or de-compression of a vehicle suspension.

97. The sonar device of claim 95, wherein the computational means comprises an algorithm that corrects for a variation in compression and/or de-compression of a vehicle suspension in response to a variation in vehicle height.

98. The sonar device according to any one of claims 1 to 67 further comprising means for correcting for a variation in terrain topography.

99. The sonar device of claim 98, wherein said means comprises computational means.

100. The sonar device of claim 99, wherein the computational means comprises an algorithm that modulates sensor height in response to a variation in terrain topography.

101. The sonar device of claim 99, wherein the computational means comprises an algorithm that corrects for a variation in terrain topography.