WO2006009472A2

WO2006009472A2 - Improved pasture meter

Info

Publication number: WO2006009472A2
Application number: PCT/NZ2005/000174
Authority: WO
Inventors: Peter Niven Schaare
Original assignee: Gallagher Group Limited
Priority date: 2004-07-16
Filing date: 2005-07-18
Publication date: 2006-01-26
Also published as: AU2005264788B2; WO2006009472A3; AU2005264788A1; NZ534189A

Abstract

The present invention relates to an improved pasture meter (1) which is adapted to indicate the amount of vegetative material (3) in a region. The pasture meter (1) includes a transmitter (5a, 5b) adapted to transmit a sound burst towards vegetation (3) in the region and a receiver (6a, 6b) adapted to detect at least one echo of a sound burst reflected from the region. The meter (1) also includes a processing means (7) adapted to receive at least one output signal from the receiver (61, 6b), this output signal being representative of an echo or echoes detected by the receiver (6a, 6b) in response to the transmission of a sound burst. This processing means (7) is adapted to determine the vegetation (3) location information and ground (4) location information from at least one echo of at least one transmitted sound burst. This vegetation (3) location and ground (4) location information is used by the processing means (7) to indicate the amount of vegetative material (3) in the region.

Description

IMPROVED PASTURE METER

TECHNICAL FIELD

This invention relates to an improved pasture meter and a method of manufacturing and operating same. Preferably the present invention may be adapted to provide a metering system which does not need to contact the ground when used. Preferably a pasture meter provided in accordance with the present invention may also be mounted and used on a vehicle, but those skilled in the art should appreciate that other applications are also envisioned.

BACKGROUND ART

In a number of instances it is of advantage to know of the extent of pasture or vegetative growth in an area. In animal husbandry applications it is of advantage for a farmer to know the amount of vegetative feed present for effective feed management. With accurate pasture yield or productivity information a livestock farmer can readily manage the movement of stock around their land and also plan for instances where additional feed will need to be supplied. Pasture productivity information can also be used to forecast yields for vegetation able to be stored as hay or silage.

However, it is presently difficult for a farmer or other interested parties to rapidly and accurately gauge the amount of feed material present in a particular pasture or paddock, and to transfer such information to farm management computer programs.

One way to determine feed levels is through a visual estimate based on an observer's perception of the volume of vegetation present, or through the use of measuring rulers or other similar mechanisms to gauge the height of vegetation and to roughly assess its density. However, as those skilled in the art can appreciate, such estimation methods are not necessarily fully accurate and also require a significant amount of time to collect a reasonable number of vegetation height samples.

There are a number of techniques available for quantifying pasture resource which rely on physical contact with the pasture and/or ground surface. One such technique to estimate pasture bulk is commonly referred to as the 'rising plate' system and uses the mechanical support of a light plate by the sward, referenced to the height of the ground surface determined by a rigid stick or probe. An example of this type of apparatus is disclosed in New Zealand Patent No. 286786. Another technique is based on measuring the capacitance between the grass sward and an adjacent insulated rod, the circuit being completed by contacting the exposed end of the conducting rod to the ground. An example of this type of apparatus is disclosed in New Zealand Patent No. 333694.

However, each of these techniques requires the device to touch the ground in order to make a measurement. This tends to make the instruments slow to operate, and precludes non-contact measurement.

One improved semi-automated system for measuring pasture density and volume has been developed and described by N. J. Hutchings, 1990 {Grass and Forage Science, Vol. 45, pp 119-127). This publication describes the provision of an ultrasonic based sward measurement stick.

The sward stick described is implemented as a fixed height walking stick with an ultrasonic emitter and detector pair at the top of the stick. Ultrasonic sound pulses are directed towards the pasture canopy with the return echoes detected being used to determine the height of the pasture when compared against the known height of the sward stick, and hence the distance to ground. This type of system uses a single frequency ultrasonic pulse train to provide information with respect to the height of the pasture to be metered or measured.

However, there are again some limitations present in the use of such an ultrasonic sward stick meter.

The sward meter provided relies on contact with the ground to set a fixed height and distance above the ground for the ultrasonic pulse transmitter. This in turn requires the operator of the meter to contact the ground for all measurements to be taken, resulting in a relatively small number of measurements being made due to the slow operation of the meter. Furthermore, some variation in the results obtained can occur with different operators using different grips or orientation angles for the sward stick meter.

It would be preferable to have an improved pasture or sward measurement system, apparatus, or method which addressed any or all of the above problems. In particular, it would be preferable to have an improved pasture meter which could operate automatically or semi-automatically to sample and measure the amount of vegetation present in the pasture or paddock, and which need not require any component of the apparatus or system to contact the ground. Furthermore, it would also be preferable to have an improved pasture or sward meter system, apparatus or method which could be deployed and used automatically from a vehicle, or which could be carried easily by an operator without necessarily requiring the operator to contact any portion of the meter to the ground.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF INVENTION

According to one aspect of the present invention there is provided a pasture meter adapted to indicate the amount of vegetative material in a region, said pasture meter including

a transmitter adapted to transmit at least one sound burst towards vegetation in the region, and

a receiver adapted to detect at least one echo of a sound burst reflected from the region, and

a processing means adapted to receive at least one output signal from the receiver, wherein said output signal is representative of an echo or echoes detected by the receiver in response to the transmission of a sound burst,

said processing means being adapted to determine vegetation location information and ground location information from an echo or echoes of at least one transmitted sound burst, said vegetation location information and ground location information being used by the processing means to indicate the amount of vegetative material in said region.

The present invention is adapted to provide a pasture meter which preferably can be used to indicate the amount of vegetative material present within a pasture, paddock, field or other related area. These types of regions can be used in agricultural or animal husbandry applications which use vegetative material as feedstock. The vegetation material grown can be grazed by livestock, or harvested to provide a store of feed for later distribution to livestock. The pasture meter provided may be used to indicate the amount of such vegetative material present in the region, as discussed below.

Preferably the vegetative material to be assessed or metered in conjunction with the present invention may include a vegetative crown, extending down through a main body and terminating at a root system extending into the ground in which the vegetation is growing. The amount of vegetative material available for grazing or harvest will therefore be dictated by the amount of material available above ground. Many different measures for the amount of vegetative material may be implemented through the use of the present invention such as for example, volumes, densities or weights of vegetative material depending on the application on which the present invention is used.

Reference throughout this specification will in the main be made to the present invention using or determining vegetation location information and ground location information to form an indication of the amount of vegetative material in a region. Furthermore reference throughout this specification will also be made to vegetation location information and ground location information being determined from the transmission of the same sound burst transmitted towards a region. However, those skilled in the art should appreciate that this technique need not necessarily be considered essential to the implementation of the present invention. For example, in one alternative embodiment vegetation location information and ground location information may be determined from the echoes of different sound bursts transmitted towards the same region.

In a preferred embodiment the pasture meter provided may be adapted to store a plurality of different indications of vegetation amounts to potentially allow for an averaged value or amount to be calculated for a greater or larger region of interest.

In such instances a single measurement or measurement step may be used to provide information with respect to a relatively small region, where a plurality of such measurement steps or recordings may be averaged together to provide information on a large region if required.

In a preferred embodiment the region within which the pasture meter provided may determine vegetative amounts may be approximately 0.5 m². The pasture meter provided may be used to sample numerous regions of such size to provide a reasonably accurate average pasture yield value for a greater conglomerate region such as a paddock or field.

Preferably a pasture meter provided in accordance with the present invention may incorporate or include a transmitter. Such a transmitter may be adapted to transmit a sound burst towards the region in which vegetative growth or material is to be metered. Those skilled in the art should appreciate that numerous and various different forms of components may be employed to form such a transmitter, depending on the specific characteristics of a sound burst or bursts to be transmitted.

In a further preferred embodiment a transmitter may be adapted to transmit an ultrasonic sound burst towards the region or pasture to be metered. An ultrasonic sound burst can be readily reflected from the ground, vegetation, and other elements in the region under investigation, with an ultrasonic echo or echoes being subsequently detected and measured.

The transmitter provided is adapted to transmit at least one sound burst towards vegetation in a region under investigation. A sound burst may consist of a variety of different forms of sound based signals. For example, in some instances a sound pulse or impulse may be generated consisting of a short duration and yet high intensity sound signal transmission. Alternatively a sound burst may be provided by a frequency sweep or chirp signal which consists of a sound frequency which changes over time and traverses a band or spectrum of frequencies. Yet in other embodiments a sound burst may be formed from a "white noise" transmission, being a signal with a continuous power spectrum across a wide band of frequencies. In further embodiments a sound burst may be formed from the transmission of one or series of discreet fixed tone sound signals over time.

Reference throughout this specification will however be made to a sound burst being formed from a sound pulse or impulse, or a comparatively long duration fixed tone signal. However, those skilled in the art should appreciate that other forms of sound bursts are able to be used in conjunction with the present invention and reference to the above only throughout this specification should in no way be seen as limiting.

In a preferred embodiment the transmitter may be adapted to emit an ultrasonic sound pulse which extends across a specific frequency band. The use of such a multi-frequency or plural frequency pulses allows return echoes to be measured effectively for various different elements or objects in the region under investigation. For example, a range of frequencies may be selected for a pulse used where the higher frequencies employed can provide good ultrasonic reflections from vegetation, while the lower frequencies in the band may provide stronger reflections from the ground in which such vegetation is growing.

In a further preferred embodiment an ultrasonic pulse transmitted may exhibit a substantially continuous or optimised power spectrum across the frequency band of sound waves making up the pulse transmitted. A continuous power spectrum for a transmitted pulse can provide echoes from objects of widely differing sizes or spatial scales. The power spectrum involved may also be optimised by the design and operation of the transmitter, depending on the materials from which echoes are to be detected.

In one alternative embodiment a transmitter means may generate an electrical spark which allows an acoustic signal of a broad band of frequencies to be transmitted at very high power levels at low cost. These high power levels can be used to overcome the high levels of ambient noise present in some environments and particularly in proximity to vehicles.

In another alternative embodiment an electrostatic ultrasonic transducer may be employed. Such transducers exhibit broad ultrasonic frequency response (e.g. 4OkHz - 100kHz). Furthermore such components may also function simultaneously as both a transmitter and a receiver of acoustic signals. Those skilled in the art should readily appreciate that the present invention may incorporate both a transmitter and receiver formed from a single component in such embodiments.

However in a preferred embodiment a transmitter means adapted to generate an ultrasonic sound pulse or impulse may be provided through a piezo electric based ultrasonic transducer well known in the art. These types of transducers or transmitters may function effectively and predictably to generate the form of ultrasonic sound pulse required.

Reference throughout this specification will also be made to an ultrasonic pulse transmitted having or incorporating a band of specific frequencies and also having a continuous power spectrum across all frequencies or optimised power spectrum across all desired frequencies within the band encompassed. However, those skilled in the art should appreciate that other types of pulses may also be emitted

(such as fixed frequency tones or collections of tones) and reference to the above only throughout this specification should in no way be seen as limiting.

For example, in other embodiments non-continuous frequency signals may make up a substantially instantaneous pulse with approximately the same power being present in each frequency selected for incorporation in the pulse. Examples of transmitters capable of generating ultrasonic, non-continuous acoustic pulses include spark or plasma generators, electrostatic speakers and transducers, piezo transducers and magnetic coil-driven devices.

In other embodiments a sound burst transmitted may not necessarily be an ultrasonic sound pulse as discussed above. For example, in such other embodiments, a comparatively long duration fixed tone or monotone ultrasonic sound signal may be transmitted as a sound burst. In such instances the type of transmitter selected may preferably be a resonant ultrasonic transducer. For such embodiments the frequency of the ultrasonic tone transmitted may preferably be in the order of 4OkHz, but those skilled in the art should appreciate that such a specific frequency should not be considered essential to the operation of the present invention.

Preferably a pasture meter provided in accordance with the present invention may include at least one receiver adapted to detect one or more echoes of a sound burst reflected from the region to be metered. Those skilled in the art should appreciate that many appropriate types of hardware or components may be employed to form such a receiver depending on the characteristics of the sound burst transmitted.

In a further preferred embodiment a pasture meter may include a single receiver only. A single receiver may be adapted to provide adequate information with respect to the specific region of interest. However, those skilled in the art should appreciate that a plurality of receivers may also be provided if required, for example to provide improved spatial location of echo sources.

In a preferred embodiment a receiver employed by or within a pasture meter may be adapted to receive, detect or otherwise measure a plurality of echoes sourced from the reflection of a sound burst within the region to be metered. Those skilled in the art should appreciate that various different echoes will be generated through the reflection of a sound burst by different materials located at different distances from the original transmitter employed. Any number of separate and distinct echoes will therefore be reflected towards a receiver which can in turn detect these echoes.

In some alternative embodiments, a receiver may be formed from a condensor microphone. Condensor microphones have an appropriate frequency response to ultrasonic sound and can therefore adequately detect the reflected echoes of interest in conjunction with the present invention. Another option in an alternative embodiment would be to use the same device as both the transmitter and the receiver, which is not practical with condensor microphones. For example, a suitable device in such cases would be an ultrasonic transducer, which both sends and receives. However, in a preferred embodiment a receiver may be formed from a customised ultrasonic transducer which is adapted to generate an electrical output signal in response to excitation by an incoming ultrasonic sound echo. Those skilled in the art should appreciate that such receiver based ultrasonic transducers are well known in the art and may be readily adapted for use with the present invention.

In such cases reference throughout this specification will also be made to a receiver being formed from a customised ultrasonic transducer adapted to generate an electrical output signal when excited by an incoming ultrasonic sound echo. Those skilled in the art should appreciate that other types of transducers may also be employed in alternative embodiments.

Preferably the receiver used may be adapted to emit or produce at least one output signal representative of the echoes it detects from a sound burst. Such an output signal may provide a trace or representation of all echoes generated by a sound burst through the operation of whichever transducer is employed as a receiver. In such embodiments the receiver may generate and emit multiple output signals over time in conjunction with the transmission of multiple sound bursts from the transmitter.

Preferably a pasture meter provided in accordance with the present invention may also include a processing means. Such a processing means may be adapted to receive an output signal from the receiver and to in turn determine or indicate the amount of vegetation or vegetative material present in the region currently being investigated. Preferably a processing means may be used to differentiate between various echoes represented within a receiver output signal generated through the transmission of a sound burst.

In a further preferred embodiment a processing means may be adapted to determine vegetation information from an echo or echoes represented within a receiver output signal. Vegetation information may be inferred, calculated or otherwise determined from the identification of a specific echo caused by the reflection of a transmitted sound burst from the vegetation present within the region under investigation.

Preferably the present invention is adapted to determine both ground location and vegetation location information to in turn allow a determination of how much pasture is present in a particular region. Preferably, the vegetation location information determined may indicate the position or location of the top or crown of the pasture present within a particular region. In combination with ground location information, this vegetation location information can be used to indicate both the height of the pasture present as well as isolating out the sections of the receiver output signal which are contributed via vegetative echoes only.

Preferably the processing means may also be adapted to determine ground location information from a sound echo present within a receiver output signal. Ground location information may be inferred, calculated or otherwise determined from the identification of a specific echo caused by the reflection of a transmitted sound burst from the ground in the region under investigation. Ground location information may indicate the location of the ground which vegetation is growing.

In a further preferred embodiment the time at which the ground echo is determined can provide a mark or reference time to divide the portions of the receiver output signal between ground echoes and vegetation echoes. In such embodiments the receiver output signal may start after the transmission of a pulse so that all portions of the reference signal prior to the detection of the ground echo can be associated with vegetative echoes. Conversely in other embodiments the original transmitted pulse may form part of the receiver output signal. As the time of transmission of the original pulse is known, a clear distinction can still be made with respect to the portions of the receiver output signal associated with vegetative echoes, and a ground echo or echoes.

In embodiments where a short duration pulse type sound burst is transmitted, the echo within a receiver output signal associated with a reflection of a pulse from the ground may have the highest amplitude or peak trace of all echoes present within the receiver output signal. The time at which this particular high amplitude pulse echo is received can therefore be used to calculate location information for the ground in a region. Through considering the speed of the ultrasound pulse and the propagation delay it experiences, a distance from transmitter to ground may be calculated.

In such instances vegetation location information associated with the crown or head of the pasture may be determined by the initial portion of the receiver signal which exceeds a set threshold amplitude value. In such instances once the receiver signal breaches a background noise level threshold a positive identification of a signal sourced from pasture or vegetation may be made, therefore positively determining the start of the vegetative echo or echoes detected.

In other embodiments such processing techniques used to determine ground and vegetative location information may not necessarily be used. For example, in one other embodiment where a comparatively long single tone signal is transmitted, the received signal is made up of a combination of echoes from various depths of the pasture and ground.

In such instances there will be an interleaving of signal components present within a receiver signal from both vegetation and the ground when the later portions of the receiver signal are considered. In such embodiments a threshold characteristic of the rising edge of the initial echo based portion of a receiver signal may be considered to isolate the start of the vegetative echo contribution to the receiver signal, and hence the vegetative location information.

A similar approach may also be taken with respect to a falling edge threshold characteristic of the receiver signal to indicate the portion of the receiver signal contributed by ground echoes. Again those skilled in the art should appreciate that a threshold characteristic, value, parameter, or rate of change of such a falling edge may indicate the start of ground based echoes being detected by a receiver.

In a further preferred embodiment these threshold characteristics used to represent the start of vegetative echoes and the start of ground echoes may be determined by empirical calibration trials. Those skilled in the art should appreciate that a large number variables are present in the determination of such thresholds from both the environment in which pasture is growing, to the plant species make up of the pasture involved. Those skilled in the art should appreciate that these thresholds for identifying both ground and vegetation location information may readily be determined through such calibration trials.

In some embodiments a signal validation process may also be executed with respect to the receiver output signal sampled or captured. A determination may be made as to the level of ambient noise present within the environment in which the pasture meter is used during time periods between the end of the transmitted pulse and the beginning of the received signal and immediately after the end of the received signal. At these times an echo is not expected from pasture or the ground. In such embodiments a corruption noise threshold level may be set, which when exceeded in such time periods will result in the related captured receiver output signal being rejected as noise corrupted.

For example, in one preferred embodiment a two to three millisecond period immediately after the transmission of a pulse based sound burst may be identified as a time period in which only ambient background noise should be present within a receiver output signal. If the level of the receiver output signal within this time period exceeds the corruption noise threshold the subsequent incoming echoes detected can be rejected as noise corrupted. A similar approach should also be taken for the known time period immediately following reception of the ground echo when all expected echoes should have been received. Again an assessment of ambient environmental noise levels may be made to determine whether the current window or set of echoes sensed should be invalidated as noise corrupted.

In a preferred embodiment multiple sound burst transmissions are made towards a single region and the resulting receiver output signals are compared to detect noise corruption of one or more of said receiver output signals. In such embodiments a plurality of echo sets generated by multiple sound bursts transmitted towards a same region may be compared and any set of echoes which are outside of a conformity tolerance may be discarded. A comparison may be made between such "adjacent" echo signals to detect clearly erroneous signals and to remove same from consideration when a vegetative amount measure is to be calculated for the region involved.

In a preferred embodiment vegetation information may be extracted from the portion of the receiver output signal associated with vegetation echoes using any number of different digital signal processing techniques.

For example, in one embodiment the peak or average amplitude of the signal trace associated with a vegetative echo or echoes may be measured to provide vegetation information. Such peak trace information can indicate the strength of the return echo and hence density of vegetation present within the region under investigation. Alternatively an average amplitude trace can again indicate the strength of a return echo and hence the density of vegetation present within the region involved. However, the strength of the return signal echo will vary with distance from the transducer and with attenuation due to varying density of material throughout the signal path. The density of the vegetation may also have an effect on the strength of a return signal echo with higher density vegetation reflecting back more of the original transmitted pulse energy than lower density vegetation.

In other embodiments the power density of a portion of the received signal associated with vegetative echoes may be investigated or measured to provide vegetation information. The power density of such vegetative echo traces may in some instances provide a reasonably accurate representation of the amount of vegetative material present within a region while taking into account both the height and also the density of vegetation present.

In yet other embodiments the isolated vegetative echo portions of a receiver signal may be integrated with respect to time to allow vegetative information to be determined. Such an integration may potentially provide pasture volume, mass and/or density information in some instances.

In a preferred embodiment the pasture meter provided may indicate vegetative amounts through passing the extracted vegetation information through a scaling or calibration based function. Prior calibration of the pasture meter with known amounts, vegetation varieties, volumes, densities or weights of vegetative material may provide a scaling function to link characteristics of an echo to actual vegetation amount readings. Furthermore such calibration or scaling functions may also take into account seasonal variation in the characteristics of return echoes measured to take into account for example, additional moisture present on the pasture or alternatively pasture being overly dry. In a further preferred embodiment such a calibration function may be empirically determined. In a preferred embodiment the pasture meter provided may indicate the amount of vegetative material present in a region through the collection or averaging of results obtained from multiple receiver output signals in turn generated by the transmission of multiple sound pulses. In such embodiments multiple sound burst transmissions may be made towards a single region and an average value of indications of the amount of vegetative material present may be stored. In effect, multiple samples of the same region may be recorded to improve the accuracy of the resulting system and hence any ground location and vegetation information employed to arrive at a vegetation amount indication.

In a preferred embodiment the pasture meter provided may also include a positioning system adapted to sense or indicate a current position value for the pasture meter. In a further preferred embodiment such a positioning system may also be adapted to record position values with vegetative amounts recorded for the particular location or region involved. Such positioning systems may allow for the display of maps illustrating large areas of pasture and the associated vegetative amounts recorded or logged for these regions.

In a further preferred embodiment a pasture meter provided may also include a GPS (global positioning satellite) receiver. GPS co-ordinates are well known in the art and may readily be mapped onto known areas or regions to allow the amounts of pasture vegetative material present in such regions to be illustrated.

In a preferred embodiment the present invention may also be adapted for use in conjunction with a vehicle. A vehicle may be employed to traverse regions relatively quickly where pasture is growing while the pasture meter provided may rapidly sample or measure the pasture present within such regions. In such embodiments a further filtering operation may be applied to an output signal derived from a receiver. This filtering operation may be used to eliminate, reduce or remove noise components generated by the operation of the vehicle involved. For example, in one preferred embodiment a high frequency pass filter may be used to remove relatively low frequency sound components from a receiver output signal where these low frequency signals are sourced from the movement of the vehicle and associated motor noise of the vehicle.

The present invention may provide many advantages over existing methods of measuring pasture.

Through the calculation or determination of ground location information the pasture meter provided need not necessarily be placed in contact with the ground when used. Calculating the ground location allows the position or orientation of the pasture meter to be varied without necessarily requiring an independent ground measurement to be made prior to the pasture meter being used. This can allow the meter provided to be mounted on a vehicle and employed to make a plurality of measurements or recordings automatically as the vehicle involved progresses through a relatively large conglomerate region to be investigated.

Such a pasture meter may be adapted to function automatically or semi- autonomously to generate a large number of readings or indications of the pasture present in individual regions. These multiple readings can then be subsequently averaged to indicate the amount of pasture present in a relatively large area such as a paddock or field.

Mounting such a pasture meter on a vehicle allows an operator and the meter to be moved rapidly over large distances while concurrently making large numbers of measurements or recordings of vegetative amounts.

Furthermore, the pasture meter provided may also be carried by an operator or user if required. An operator need not necessarily hold, carry or otherwise position the pasture meter at a fixed distance above ground to allow for effective and fast operation of the meter. Again, a meter implemented in such an embodiment may simply be carried and be adapted to function semi-autonomously to make a significant number of measurements as an operator moves over a relatively large region.

This may be contrasted with prior art pasture measurement techniques where the apparatus used needs to make contact with the ground to provide a dedicated height measurement. As can be appreciated by those skilled in the art, this can significantly slow the progress of an operator and limit the number of measurements they may make in a set period of time when compared with a pasture meter provided in accordance with the present invention.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

Figure 1 shows a block schematic diagram of components employed to provide a pasture meter in accordance with a preferred embodiment; and

Figures 2a & 2b show representations of a receiver output signal when used to measure differing amounts of vegetation present within a region when a sound pulse is transmitted, and

Figure 3a, 3b provide comparative amplitude versus time plots of transmitter and processed receiver signals in an embodiment where a comparatively long duration mono-frequency sound signal is transmitted as a sound burst. Figure 4 shows a flowchart of signal processing steps executed in accordance with an embodiment where a pulse based sound burst is transmitted, and

Figure 5 shows a flowchart of signal processing steps executed in accordance with an embodiment where a comparatively long duration mono-frequency signal is transmitted as a sound burst.

BEST MODES FOR CARRYING OUT THE INVENTION

Figure 1 shows a block schematic diagram of components employed to provide a pasture meter in accordance with a preferred embodiment.

Figure 1 illustrates a pasture meter (1) disposed above pasture (2) formed by vegetative material (3) growing out of the ground surface (4).

The pasture meter (1 ) is formed from a transmitter (5a, 5b), a receiver (6a, 6b) and a processing means (7). Those skilled in the art should also appreciate that a single transceiver device may also be used in some instances to implement the transmitter and receiver together.

The transmitter (5a, 5b) is implemented in this embodiment through a pulse generation and shaping system (5a) connected to a transducer head (5b). The pulse generator (5a) is used to form an electrical driving signal pulse which when received by the transducer head (5b) will generate an ultrasonic sound pulse with a power spectrum which spans a specific band of ultrasonic sound wave frequencies. This power spectrum will be dictated by the configuration and type of transducer employed, and the driving signal applied to same. Those skilled in the art should also appreciate that if sound bursts other than sound pulses are to be transmitted the transducer head (5b) can again be modified to generate the particular type of sound burst required. The receiver (6a, 6b) is in this instance made up of a condensor microphone (6a) linked to an analogue to digital converter in the form of an acoustic receiver (6b). The microphone (6a) detects reflected ultrasonic sound pulse echoes from the vegetative material (3) and ground surface (4) and converts these into an analogue electrical signal for subsequent supply to the acoustic receiver (6b). The acoustic receiver (6b) then converts the analogue signal received into a digital receiver output signal for subsequent transmission to the processing means (7).

The processing means is implemented in a preferred embodiment by a microprocessor or digital signal processor employed to provide a data acquisition system (7). The data acquisition system (7) receives the digitised receiver output signal and executes a digital signal processing algorithm initially to detect the pasture height and ground level echoes present within the receiver signal.

When the times that these two events occur are identified, a section of the remaining trace or portions of the receiver output signal can then be associated with the vegetation or vegetative growth (3) to be measured or metered. The particular section of the remaining trace may also be identified using vegetation location information, indicated by the start of the section of the trace which exceeds a certain threshold amplitude value, thereby indicating that the start of the vegetation echo.

Figures 2a & 2b show representations of a receiver output signal when used to measure differing amounts of vegetation present within a region when a sound pulse is transmitted. In the embodiment discussed with respect to figures 2a and 2b a sound pulse type sound burst is transmitted towards a region. This pulse has a comparatively short transmission time and hence its transmission is completed prior to any return echoes reaching the receiver of the pasture meter.

Figure 2a illustrates a receiver output signal prior to digitisation by the acoustic receiver (6b) where comparatively long grass is present within the region to be measured. Conversely, figure 2b illustrates the trace present when short grass or minimal vegetative growth is present within the region metered.

As can be seen from figure 2a, the vegetation information present within the receiver (7) between the original sound pulse and the ground echo has comparatively high peaks and a higher energy density than that present with respect to figure 2b. These variable signal parameters extracted to provide vegetation information can in turn (through a calibrated scaling function) indicate the amount of vegetative material present within the region under investigation.

Figures 3a, 3b provide comparative amplitude versus time plots of transmitter and processed receiver signals in an embodiment where a comparatively long duration mono-frequency sound signal is transmitted as a sound burst.

Figure 3a illustrates the form of the signal burst transmitted, being a relatively long mono-frequency ultrasonic sound signal. Figure 3b illustrates a processed filtered receiver output signal formed in accordance with the signal processing methodology discussed with respect to figure 5.

Due to the long transmission time of the original sound burst a pair of threshold positions (2, 3) need to be identified within the processed receiver output signal envelope shown. Threshold position 2 indicates the start of the output signal trace where a contribution has started to be provided through returning echoes from the top of the pasture to be metered. Conversely, threshold position 3 indicates the position or time within the output signal trace at which the signal is composed from returning ground echoes.

Figure 4 shows a flowchart of signal processing steps executed in accordance with an embodiment where a pulse based sound burst is transmitted. The first step of this method is to capture the receiver signal involved. The captured signal is then supplied to a high pass filter to remove signal components present from the operation of a vehicle used in the preferred embodiment.

Next the filtered signal is processed through an absolute value function to provide only positive signal data points and to create a continuous curving waveform, defining a signal envelope.

Following this process the signal envelope generated is filtered through a further low pass filter and is ready for the subsequent determination of ground location and vegetation location information. The vegetation location information is extracted from the point in the receiver signal where the amplitude of the signal exceeds a certain threshold value above expected ambient noise levels, indicating that an echo has been received from vegetation. Next, ground location information is determined from the maximum amplitude point of the receiver signal.

Once these two location parameters have been identified, the intervening section of the signal envelope can then be analysed to determine the amount of vegetation present within the region under investigation.

A similar approach is taken in the signal processing of the sound burst involved to that discussed with respect to figure 4, which deals with the transmission of a sound pulse. However, in the case of a comparatively long single frequency signal, an allowance has been made for the overlap in transmitter signal with incoming echoes due to the transmit time of the sound burst involved.

In such instances the receiver signal is captured and subsequently supplied to a forward backward pass filter which is adapted to remove vehicle noise components from the signal and also preventing phase errors being introduced into the signal.

Subsequently, an absolute value function is again applied and a signal envelope is formed from results of this function. The data present in the envelope provided is then smoothed through an averaging function.

Lastly, the characteristics of the resulting smoothed receiver data envelope are investigated to locate two thresholds within the receiver signal curve indicative of the start of vegetation based echoes and the start of ground reflection based echoes. These thresholds are present on the rising edge of the envelope curve for vegetation location information, and the falling edge of the curve for ground location information. Preferably each of these thresholds is determined by an empirical calibration process due to seasonal and environmental variables which need to be adjusted for.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.

Claims

WHAT WE CLAIM IS:

1. A pasture meter adapted to indicate the amount of vegetative material in a region, said pasture meter including;

a transmitter adapted to transmit a sound burst towards vegetation in the region, and

said processing means being adapted to determine vegetation location information and ground location information from at least one echo of at least one transmitted sound burst, said vegetation location and ground location information being used by the processing means to indicate the amount of vegetative material in said region.

2. A pasture meter as claimed in claim 1 wherein the transmitter is adapted to transmit an ultrasonic sound burst.

3. A pasture meter as claimed in claim 2 wherein the transmitter is adapted to emit an ultrasonic sound pulse which extends across a specific frequency band.

4. A pasture meter as claimed in claim 3 wherein the higher frequencies of the band provide effective ultrasonic reflections from vegetation within the region, and the lower frequencies in the band provide effective ultrasonic reflections from the ground in the region.

5. A pasture meter as claimed in any one of claims 2 to 4 wherein an ultrasonic pulse transmitted exhibits a substantially constant power spectrum across the frequency band of the pulse.

6. A pasture meter as claimed in claim 1 or claim 2 wherein the transmitter is adapted to emit a monotone ultrasonic sound transmission.

7. A pasture meter as claimed in any previous claim wherein vegetation location information represents the crown of the pasture to be metered.

8. A pasture meter as claimed in any previous claim wherein ground location information indicates the location of the ground in which vegetation is growing.

9. A pasture meter as claimed in any previous claim wherein ground location information and vegetation location information are determined from the echoes of different sound bursts transmitted towards the same region.

10. A pasture meter as claimed in any previous claim wherein multiple sound burst transmissions are made towards a single region and an average value of indications of the amount of vegetative material present in the region is stored by the pasture meter.

11. A pasture meter as claimed in any previous claim wherein multiple sound burst transmissions are made towards a single region and the resulting receiver output signals are compared to detect noise corruption of one or more of said receiver output signals.

12. A pasture meter as claimed in any previous claim wherein a piezo electric transducer is provided as a transmitter.

13. A pasture meter as claimed in claim any one of claims 1 to 11 wherein a resonant ultrasonic transducer is provided as a transmitter.

14. A pasture meter as claimed in any previous claim wherein the highest amplitude peak present within the receiver output signal provides ground location information.

15. A pasture meter as claimed in any one of claims 1 to 13 wherein a falling edge threshold characteristic of a receiver output signal provides ground location information.

16. A pasture meter as claimed in claim 15 wherein said falling edge threshold characteristic is determined by an empirical calibration trial.

17. A pasture meter as claimed in any previous claim wherein the breach of a background noise level threshold within a receiver output signal provides vegetation location information.

18. A pasture meter as claimed in claim any one of claims 1 to 16 wherein a rising edge threshold characteristic within a receiver output signal provides vegetation location information.

19. A pasture meter as claimed in claim 18 wherein said rising edge threshold characteristic is determined by an empirical calibration trial.

20. A pasture meter as claimed in any previous claim wherein a signal validation process is executed with respect to a receiver output signal to accept or reject said receiver output signal.

21. A pasture meter as claimed in claim 20 wherein a threshold corruption noise level is compared to at least one section of an output receiver signal to execute a signal validation process.

22. A pasture meter as claimed in any previous claim wherein a peak amplitude value of the receiver output signal associated with vegetation echoes provides vegetation information.

23. A pasture meter as claimed in any one of claims 1 to 21 wherein an average amplitude of the receiver output signal associated with vegetation echoes provides vegetation information.

24. A pasture meter as claimed in any one of claims 1 to 21 wherein the power density of the received output signal associated with vegetation echoes provides vegetation information.

25. A pasture meter as claimed in any one of claims 1 to 21 wherein a time based integration of the receiver output signal associated with vegetation echoes provides vegetation information.

26. A pasture meter as claimed in any previous claim wherein the receiver output signal associated with vegetation echoes is passed through a selected empirically determined calibration function to determine the amount of vegetative material in the region.

27. A pasture meter as claimed in any previous claim which includes a positioning system adapted to record the position of a region in combination with a pasture amount indicated for said region.

28. A pasture meter as claimed in claim 27 which includes a GPS receiver.

29. A pasture meter as claimed in any previous claim wherein the receiver output signal is filtered to remove vehicle based noise.

30. A method of manufacturing a pasture meter substantially as herein described with reference to and as illustrated by the accompanying drawings and/or examples.

31. A pasture meter substantially as herein described with reference to and as illustrated by the accompanying drawings and/or examples.