GB2604155A

GB2604155A - A spraying detection system and method

Info

Publication number: GB2604155A
Application number: GB2102768.5A
Authority: GB
Inventors: Pejovic Vukasin; Tadic Srdjan; Vukajlovic Milan; Milojevic Slobodan
Original assignee: Atfield Tech Doo
Current assignee: Atfield Tech Doo
Priority date: 2021-02-26
Filing date: 2021-02-26
Publication date: 2022-08-31
Also published as: GB202102768D0

Abstract

A spraying detection system for monitoring crop spraying events comprising a plurality of sensor units and a control unit. The plurality of sensor units are distributed in the field where the crop is located. Each of the plurality of sensor units has a humidity sensor, a memory and a communication module. The control unit has a communication module for communication with the plurality of sensor units, a memory and a processor having control logic to process the humidity data and detect a crop spraying event. The control logic uses humidity data from multiple sensors to determine whether it is a spraying event that is being recorded and if so, the spraying event is recorded. The spraying event can be used to create a spraying record and spraying history which may be used by interested parties.

Description

"A spraying detection system and method"

Introduction

This invention relates to a spraying detection system and method. More specifically, this invention relates to a spraying detection system for monitoring crop spraying events and a spraying detection method for monitoring crop spraying events.

Spraying and dusting, in agriculture, are the standard methods of applying pest-control chemicals and other compounds to crops. Sprays and dusts are used to control insects, mites, fungous and bacterial diseases of plants; insects; and weeds, by means of chemical weed killers, herbicides and more recently organic and neutral compounds. By neutral, what is meant is compounds that are neutral to the environment that will allow the crops to which they are applied to be used almost instantly after the neutral compounds have been applied to them. Sprays and dusts may also be used for other special purposes such as applying mineral fertilizers, increasing or decreasing fruit set, delaying the dropping of nearly mature fruits, and defoliating and vine killing to facilitate the harvest of plants such as cotton or potatoes.

All preparations that are applied to crops can influence human health, particularly if the preparations are not applied according to the correct safety guidelines. In addition, there are a number of pesticides that are now banned from crops for human or animal consumption. Generally speaking, all preparations have a defined minimum time period after application before harvesting of the crop to which they are applied can begin.

Following these rules is now in the hands of farmers, who are effectively self-regulated.

US4315317 is understood to disclose a system in which there is provided a sensor to measure the quantity of chemicals that are applied to a particular crop. CN202551810U is understood to disclose a system which uses a soil humidity sensor for the purposes of irrigation automation, namely, to determine when it is necessary to hydrate a crop.

It is envisaged that it would be useful to provide a system and method that could detect a crop spraying event and log that crop spraying event in an accessible memory for use by farmers and/or consumers. Heretofore, there are no known systems or methods used -2 -specifically for monitoring and detecting crop spraying events in this manner. It is an object of the present invention to provide a system and method for monitoring and detecting crop spraying events that overcomes problems in the art and that provides a useful choice to the consumer.

Statements of Invention

According to the invention there is provided a spraying detection system for monitoring crop spraying events comprising: a plurality of sensor units for distribution in the field where the crop is located, each of the plurality of sensor units having a humidity sensor, a memory for storage of humidity data captured by the humidity sensor, and a communication module for transmission of the humidity data captured by the humidity sensor; and a control unit having: a communication module for communication with the plurality of sensor units and receipt of the humidity data captured by the humidity sensors, a memory for storage of humidity data received from the plurality of sensor units and storage of spraying events, and a processor having control logic for processing the humidity data and detecting a spraying event.

By having such a system, the system can monitor and report spraying events of agriculture crops. This has many benefits for many disparate parties. For the farmers, the system can be used to generate a spraying summary report that can help them manage their crops and can be provided to third parties as evidence of when spraying occurred. In addition, the farmers can use this information to plan their next actions, for example when the next spraying operation may be necessary. For organic producers, this information can serve as a tool of proof to their consumers that artificial pesticides and the like have not been strayed on their crop. At the same time, the spraying history can be used to build confidence with consumers, as the spraying history will provide proof of the last spraying event and that the crop has been handled properly. For example, all interested third parties can be informed if enough time has passed between the last spraying and the harvest of the crop. -3 -

By having multiple sensor units spread across the field, it is possible to differentiate spraying from other events and reliably detect a spraying event as just that. This detection of a spraying event can then be used to create an electronic diary, so this information can be used to good effect by the farmer, suppliers and/or consumers.

Other offerings in the art are focused on precision agriculture and automation. None of the previously known systems is focused on sensing spraying for spraying diaries or proving absence of spraying and correlation with harvesting, so interested third parties could become aware that products are safe for use or distribution. The aim of those systems is to precisely apply chemicals. Advantageously, the system according to the present invention is used to detect spraying events which can be used to automate a spraying diary, and for monitoring spraying dates to match those spraying dates with harvesting conditions.

In one embodiment of the invention there is provided a spraying detection system in which the control unit has means to generate a crop spraying report and store that crop spraying report in memory. The crop spraying report may include the date and time of the spraying event as well as other information such as duration, extent, type of spraying event and the like.

In one embodiment of the invention there is provided a spraying detection system in which the control unit is provided with means to add the crop spraying report to a crop spraying history and store the crop spraying history in memory. By having a crop spraying history in memory, a farmer or third party with access to the crop spraying history will have a full history of the spraying events that have happened over the lifecycle of the crop. This can be useful for the farmer's planning and organization as well as satisfying suppliers and regulators as to what treatments have been applied to the crop over its lifetime.

In one embodiment of the invention there is provided a spraying detection system in which the control unit is provided with means to determine the earliest available harvest date upon generation of a crop spraying report. This is seen as a useful aspect of the invention in that the system can determine, once a spraying event has been detected, when it will be possible to harvest the crop. -4 -

In one embodiment of the invention there is provided a spraying detection system in which the control unit further comprises a sensor unit. In this way, the control unit may also perform the functions of a sensor unit and carry out sensing operations on the crop. The control unit will be located in the field with the crop and one or more other sensor units.

In one embodiment of the invention there is provided a spraying detection system in which the sensor units further comprise a compound detection unit operable to determine the type of compound being sprayed on the crop during the spraying event.

This is seen as a particularly preferred embodiment of the invention as not only with the spraying event be detected by the compound being sprayed on the crop will also be ascertained. This will be useful for reporting purposes, record keeping and crop management. It will also be of interest for regulatory purposes and product tracing.

In one embodiment of the invention there is provided a spraying detection system in which the sensor units further comprise means to determine the amount of compound being sprayed on the crop during the spraying event. Again, this will be useful for reporting purposes, record keeping and crop management. It will also be of interest for regulatory purposes and product tracing.

In one embodiment of the invention there is provided a spraying detection system in which the plurality of sensor units are distributed remotely from each other in a field. Once the sensors are positioned in the field, the distance between the sensor and the nearest adjacent sensor is determined and recorded. Similarly, the position of the sensor and its distance to the nearest adjacent sensor can be determined using Global Navigation Satellite System (GNSS) or similar methodology for determining the position of the sensor.

In one embodiment of the invention there is provided a spraying detection system in which there is provided a remote memory for storage of one or more of a crop spraying event, a crop spraying report and a crop spraying history. Preferably, the remote memory is cloud-based. This is seen as a preferred aspect of the invention as the cloud-based data will then be accessible from many disparate devices. Indeed, the control unit and the processing functionality of the control unit may also be cloud-based. In addition, -5 -the data can be stored safely and measures may be put in place to prevent alteration or deletion of data that has been stored in the cloud storage, and/or to monitor changes that have been made and by whom those changes have been made.

In one embodiment of the invention there is provided a method of detecting a crop spraying event comprising the steps of: placing a plurality of sensor units in a field containing the crop to be monitored, each of the plurality of sensor units having a humidity sensor, a memory for storage of humidity data captured by the humidity sensor, and a communication module for transmission of the humidity data captured by the humidity sensor; transmitting the humidity data from each of the sensor units to a control unit having a processor with control logic thereon; the control unit processing the humidity data from the plurality of sensor units and detecting whether a crop spraying event has occurred.

This is seen as a particularly simple method of detecting a crop spraying event. By having multiple sensor units spread across the field, it is possible to differentiate a spraying event from other events and reliably detect a spraying event. This detection of a spraying event can then be used to create an electronic diary, so this information can be used to good effect by the farmer, suppliers and/or consumers.

In one embodiment of the invention there is provided a method of detecting a crop spraying event in which the method comprises the steps of generating a crop spraying report and storing the crop spraying report in memory.

In one embodiment of the invention there is provided a method of detecting a crop spraying event in which the method comprises the steps of adding the crop spraying report to a crop spraying history and storing the crop spraying history in memory.

In one embodiment of the invention there is provided a method of detecting a crop spraying event in which the method comprises the step of determining the earliest available harvest date upon generation of a spraying report. -6 -

In one embodiment of the invention there is provided a method of detecting a crop spraying event in which the control unit comprises a sensor unit and the method further comprises the steps of the control unit sensing the humidity and storing the humidity data in memory.

In one embodiment of the invention there is provided a method of detecting a crop spraying event in which the sensor units further comprise a compound detection unit and the method comprises the step of the sensor units determining the type of compound being sprayed on the crop during the spraying event.

In one embodiment of the invention there is provided a method of detecting a crop spraying event in which the sensor units further comprise means to determine the amount of compound being sprayed on the crop during the spraying event and the method comprises the step of determining the amount of compound being sprayed on the crop during the spraying event.

In one embodiment of the invention there is provided a method of detecting a crop spraying event in which the method comprises the initial step of distributing the sensor units remotely from each other in a field containing the crop.

In one embodiment of the invention there is provided a method of detecting a crop spraying event in which there is provided a remote memory and the method comprises the step of storing one or more of a crop spraying event, a crop spraying report and a crop spraying history in the cloud based remote memory. Preferably, the memory is cloud-based memory. -7 -

Detailed Description of the Invention

The invention will now be more clearly understood from the following description of some embodiments thereof given by way of example only with reference to the accompanying drawings, in which:-Figure 1 is a diagrammatic representation of a spraying detection system according to the invention; Figure 2 is a diagrammatic representation of an alternative embodiment of spraying detection system according to the invention; Figure 3 is a diagrammatic representation of a control unit; Figure 4 is a diagrammatic representation of a sensor unit; Figure 5 is a flow diagram illustrating feature extraction used in the system and method according to the invention; Figure 6 is a flow diagram illustrating spatial temporal logic used in the system and method according to the invention; and Figure 7 is a flow diagram illustrating a spraying detection methodology used in the system and method according to the invention.

Referring to Figure 1, there is shown a spraying detection system for monitoring crop spraying events, indicated generally by the reference numeral 100, the spraying detection system comprises a control unit 200 and a plurality of sensor units 300(a)-300(d). The plurality of sensor units 300(a)-300(d) are distributed throughout a field, indicated by dashed line 400, where there is a crop to be monitored.

Each of the plurality of sensor units 300(a)-300(d) has a humidity sensor 301, a memory 303 for storage of humidity data captured by the humidity sensor 301, and a communication module 305 for transmission of the humidity data captured by the -8 -humidity sensor. The control unit 200 in turn has a communication module 201 for communication with the plurality of sensor units 300(a)-300(d) and receipt of the humidity data captured by the humidity sensors 301, a memory 203 for storage of humidity data received from the plurality of sensor units and storage of a crop spraying event, and a processor 205 having control logic for processing the humidity data and detecting a crop spraying event. The communication channels between the control unit 200 and the sensor units 300(a)-300(d) are represented by lines 500(a)-500(d) respectively.

In use, each of the sensor units 300(a)-300(d) is placed in the field remote from the other sensor units 300(a)-300(d) and the sensor units 300(a)-300(d) each monitor the humidity in the environment of the sensor unit 300(a)-300(d). The sensor units 300(a)-300(d) transmit that humidity data to the control unit 200 via their respective communication channel 500(a) to 500(d). The control unit 200 has control logic stored thereon in memory and accessible by the processor for processing the humidity data from the plurality of sensors and the control unit can detect whether a spraying event has occurred from the humidity data.

Importantly, by having the humidity data from a plurality of sensors distributed throughout the field, the control unit control logic can determine whether it is a spraying event or another event such as dew, rainfall, hailstones and the like. This will be explained in greater detail with reference to Figures 5 to 7 inclusive below. In summary, spraying events will change the humidity recorded by the sensors sequentially, aligned with the spraying pattern. More specifically, the speed of the change of humidity between the measurement points is important. Rain, rather than spraying, will change humidity at multiple sensors almost simultaneously. In this way, the present invention goes through a list of humidity changes recorded by multiple sensor units to determine a validity window. If further assurance is required, atmospheric pressure or a rain sensor could be coupled with detection of an almost simultaneous humidity change to make sure it is not a spraying event.

Fundamental to the present invention is that abrupt humidity changes at multiple locations at the same time will not happen in the case of spraying. All other meteorological phenomena will, most likely, have a similar pattern at all or at least -9 -multiple locations at the same moment. This determination of whether or not the event is a spraying event can be made more robust with the addition of more sensing elements like a pressure sensor, a temperature sensor, a rain sensor, or even a wind sensor, since spraying is generally not performed during low or very high wind speeds. Other sensors can be used to improve detection.

In the embodiment shown, each of the sensor units 300(a)-300(d) have humidity sensors however they may also each be provided with a sensor (not shown) to detect the compound being used to spray the crop as well as a sensor (not shown) to detect the quantity of the compound being used to spray the crop. The control unit 200 has control logic thereon however it will be understood that the processing could be done elsewhere, remote from the control unit. For example, the processing could be done in the cloud, as could the memory storage for the control unit. The control unit 200 could in itself be located in the field 400 and have a sensor unit 300(a)-300(d) integral therewith so that it performs both the functions of a control unit and a sensor unit.

In the embodiment shown, there are four sensor units 300(a)-300(d) however this is for illustrative purposes only and is not deemed limiting. All that is necessary is that there are a plurality of humidity sensors spread across the field containing the crop to be monitored. The system according to the invention is based on at least two sensor units (also referred to as Sensor Nodes) installed in the field, which sense humidity in real time and send data over a wireless network 500(a)-500(d) to the Central Control Unit 200. The control unit could effectively be located in the cloud. Decision logic is implemented in the control unit 200, however some pre-processing might be done on sensor nodes, but not the decision as to whether it is a spraying event or not. All the information about spraying events can be stored remotely in servers and memory in the computing cloud, referred to simply as the cloud. Sensor nodes can be enhanced with sensors to detect the type of compound, or can be improved to detect spraying quantity.

Referring now to Figure 2, there is shown an alternative embodiment of spraying detection system according to the invention, indicated generally by the reference numeral 600, and where like parts have been given the same reference numeral as before. The spraying detection system 600 comprises a control unit 200, also referred to as a gateway device, and a plurality of sensor units 300(a) -300 (c), also referred to as -10 -sensor devices, forming a sensor network 700. There is further provided a cloud-based server 800 accessible through the internet 900.

Referring to Figure 3, there is shown a more detailed view of a control unit / gateway device 200. The control unit comprises a plurality of core components including a processor 205, a humidity sensor 207, a global positioning receiver 209 and a communication module 201 which in turn comprises a short-range wireless connectivity device 211 and a long range wireless connectivity device 213. The control unit 200 further comprises a plurality of optional components including a temperature sensor 215, a rain sensor 217 and a leaf wetness sensor 219. Other components/sensors 221 could be provided if desired depending on the application and/or the location of the device. For example, an atmospheric pressure sensor, a gas sensor operable to detect a certain type of gas such as Ozone or CO2, a sensor capable of detecting cloud cover, or the like. A power supply (not shown) to power the equipment will be provided.

Referring to Figure 4, there is shown a more detailed view of a sensor unit 300. The sensor unit/sensor device 300 comprises a plurality of core components including a humidity sensor 301, a global positioning receiver 307, a processing unit 309 and a communication module which in turn comprises a short-range wireless connectivity device 311. The sensor unit 300 further comprises a plurality of optional components including a temperature sensor 315, a rain sensor 317, a leaf wetness sensor 319 and a long range wireless connectivity device 313. Other components/sensors 321 could be provided if desired depending on the application and/or the location of the device (similar to those additional sensors provided in the control unit outlined above). A power supply (not shown) to power the equipment will be provided. It will be understood that the processor/processing unit 309 will allow for a degree of pre-processing of data to be carried out in the sensor unit if desired.

Referring now to Figures 5 to 7, there are shown flow diagrams of the steps used in the system and method according to the invention.

Referring first of all to Figure 5, there is shown a flow diagram illustrating a feature extraction technique used in the system and method according to the invention, indicated generally by the reference numeral 1000. The method starts at step 1001 and in step 1003, the sensor calculates the rate of change of humidity by determining the change of humidity, AH, over a given time period, At, (AH / At). In step 1005, it is determined whether or not the rate of change of humidity, AH / At, is greater than a threshold value, THR, equal to twice the sensors operational noise. The threshold value could be set at a different value if desired other than twice the sensor's operational noise. For example, the threshold value could be set at another multiple of the sensor's operational noise, or could be based on local parameters of an installation, or could be set dynamically and adaptively depending on local conditions and/or trial and error. If the rate of change of humidity is greater than the threshold value, that is recorded as an event, Ek, at time tk, at position Pk (i.e. an event, at a given time, at a given sensor location), represented by Ek(tk, Pk) in step 1007. Once the event is recorded, the method proceeds to end step 1009. If, during step 1005, the rate of change of humidity AH / At is not greater than a threshold value, THR, no event is recorded in step 1007 and instead the method proceeds directly to end step 1009. Typically, the method cycles through these steps on a periodic basis, e.g. every few seconds or can be triggered by an event such as a change in humidity detected by the humidity sensor. The events are stored in memory for subsequent processing.

Referring now to Figure 6, there is shown a flow diagram illustrating the spatial temporal logic used in the system and method according to the invention, indicated generally by the reference numeral 1100. The method starts in step 1101 and in step 1103, the method determines the closes neighbour to a given sensor unit and calculates the distance between the sensor unit and the closest neighbour, indicated by Dk, where (k = 1,...,n). For each Dk, (or distance between the sensor at at given position Pk and its closest neighbour), the method, in step 1105, calculates the minimum required time that it would take for a tractor, a drone, a human, a horse, an ox, a robot (or other apparatus used in the spraying operation of the crop, to pass the other sensor at a certain predefined speed. This is stored as a threshold time, .THR, for that given sensor position, tkHR(Pk). In step 1107, the threshold time, tTHR, for each of the sensor positions, tthR(Pi)...

tri-in(PN) (also referred to as t1THR.ANTHR) are stored in memory before the method ends in step 1109. It is envisaged that a plurality of threshold times could be calculated and stored for each sensor position if different means (e.g. tractor and drone) are used to spray the crop.

-12 -A unique aspect of the present invention is the use of multiple sensors (sensor network) across the field to create a spatio-temporal footprint in order to perform precise spraying detection. According to the present invention, the distance between sensors and how long it would take for a second sensor to detect the spraying event after a first sensor detects a spraying event Of a farmer were spraying the crops) is determined. If both sensors detect the rise in humidity (using the humidity sensors) and the change is identified by the pair of sensors in less than a threshold time, that is determined not to be a spraying event. A key point is to detect any two or more changes of the humidity within the time frame that would correspond to the tractor performing spraying and not faster than that. So, the logic would be to not classify something as spraying if it is faster than physically possible. The change of humidity could, for example, actually be detected on one sensor only, if the two sensors are present at a similar location. This would mean that one sensor detects the change, the other does not detect the change, but as the speed of change is low, it could be a spraying event. The more sensors, the more reliable detection will be.

In addition, if all the sensors simultaneously detect high humidity practically simultaneously, that could be determined to be dew, particularly if the data is collated with time data and it is noted that it is early in the morning. Similarly, if all the sensors are detecting high humidity at nighttime or throughout the day, practically simultaneously, this is most likely a rain shower._The present invention is able to tell if the humidity change pattern is too fast for it to be spraying in which case it is determined to be one or more of dew, rain or similar.

Figure 7 is a flow diagram illustrating a spraying detection methodology used in the system and method according to the invention, indicated generally by the reference numeral 1200. The method starts in step 1201 and in step 1203, the method starts a check of all unprocessed events, Ek. If there are no unprocessed events that require processing, the method moves straight to step 1209, where the method ends. If there are unprocessed events, the method proceeds to step 1204. In step 1204, a check is made to determine: If time[now] > t [Ek] + tTHR [Rid -13 -i.e. if the current time is greater than the time of the last event, E, at the sensor location plus the threshold time for that sensor position, P. If the statement: time[now] > t [Ek] + tTHR [PR] is false, the method returns to step 1203. If the statement: time[now] > t [ER] + tTHR [Pk] is true, the method proceeds to step 1205.

In step 1205, a check is made to determine whether other events happened in the interval for each position. For each event, for that position of sensor, this test is represented by: If t[EK] -trHK[PK] < t[E1] < t[Ek] + trHK[PK] for any i, where i £{1,... N} and i # k If no other events happened, the method moves on to step 1207 where it is determined that the event EK is a spraying event that was detected at that position, and the event is removed from the queue. . The method then returns to step 1203 to check if there are any other unprocessed events. If at step 1205, it is determined that other events did happen in the interval, it is determined that the event EK is not a spraying event, the event is removed from the queue, and the method returns to step 1203 to check if there are any other unprocessed events.

There are different types of humidity sensors on the market and many of them will sense change of humidity, even during the spraying process. However, using only one sensor unit will not provide a confidence level to detect spraying as it is difficult to differentiate the spraying from other events such as rain, dew, irrigation, and the like. By using multiple sensors across the field, this will allow the system and method according to the invention to identify local changes in humidity which are consequence of spraying or another event that changes humidity parameters, but with smart processing we can differentiate the spraying from others.

By having multiple sensors across the field and a few additional sensing components, it would be possible to precisely detect different events apart from spraying such as hailstone, irrigation, microclimates, and the like. For example, a precipitation sensor, a temperature sensor, a wind sensor, and/or a solar radiation sensor may also be used to -14 -good effect to determine useful information and to determine whether or not an event is a spraying event. In the present invention, the short range radio communications are provided by way of a S2LP chipset by STMicro. The humidity is measured using LW100 by Global Water, and the microprocessor is provided by way of a STM32 by STMicro.

These are merely examples of one type of device that could be used to good effect in order to perform the invention however it will be understood that other devices with the necessary functionality could also be used to good effect.

In this specification the terms "comprise, comprises, comprised and comprising" and the terms "include, includes, included and including" are all deemed interchangeable and should be afforded the widest possible interpretation.

The invention is not limited solely to the embodiment hereinbefore shown but may be varied within the scope of the appended claims.

Claims

-15 -Claims: (1) A spraying detection system for monitoring crop spraying events comprising: a plurality of sensor units for distribution in the field where the crop is located, each of the plurality of sensor units having a humidity sensor, a memory for storage of humidity data captured by the humidity sensor, and a communication module for transmission of the humidity data captured by the humidity sensor; and a control unit having: a communication module for communication with the plurality of sensor units and receipt of the humidity data captured by the humidity sensors, a memory for storage of humidity data received from the plurality of sensor units and storage of a crop spraying event, and a processor having control logic for processing the humidity data and detecting a crop spraying event.(2) A spraying detection system as claimed in claim 1 in which the control unit has means to generate a crop spraying report and store that crop spraying report in memory.A spraying detection system as claimed in claim 2 in which the control unit is provided with means to add the crop spraying report to a crop spraying history and store the crop spraying history in memory.(4) A spraying detection system as claimed in claim 2 or 3 in which the control unit is provided with means to determine the earliest available harvest date upon generation of a spraying report.(5) A spraying detection system as claimed in any preceding claim in which the control unit further comprises a sensor unit.(3) 25 -16 -(6) (7) (8) (9) (10) (11) A spraying detection system as claimed in any preceding claim in which the sensor units further comprise a compound detection unit operable to determine the type of compound being sprayed on the crop during the spraying event.A spraying detection system as claimed in any preceding claim in which the sensor units further comprise means to determine the amount of compound being sprayed on the crop during the spraying event.A spraying detection system as claimed in any preceding claim in which the plurality of sensor units are distributed remotely from each other in a field.A spraying detection system as claimed in any preceding claim in which there is provided a cloud based remote memory for storage of one or more of a crop spraying event, a crop spraying report and a crop spraying history.A method of detecting a crop spraying event comprising the steps of: placing a plurality of sensor units in a field containing the crop to be monitored, each of the plurality of sensor units having a humidity sensor, a memory for storage of humidity data captured by the humidity sensor, and a communication module for transmission of the humidity data captured by the humidity sensor; transmitting the humidity data from each of the sensor units to a control unit having a processor with control logic thereon; the control unit processing the humidity data from the plurality of sensor units and detecting whether a crop spraying event has occurred.A method of detecting a crop spraying event as claimed in claim 10 in which the method comprises the steps of generating a crop spraying report and storing the crop spraying report in memory.-17 -(12) (13) (14) (15) (16) (17) (18) A method of detecting a crop spraying event as claimed in claim 11 in which the method comprises the steps of adding the crop spraying report to a crop spraying history and storing the crop spraying history in memory.A method of detecting a crop spraying event as claimed in claim 11 or 12 in which the method comprises the step of determining the earliest available harvest date upon generation of a spraying report.A method of detecting a crop spraying event as claimed in any one of claims 10 to 13 in which the control unit comprises a sensor unit and the method further comprises the steps of the control unit sensing the humidity and storing the humidity data in memory.A method of detecting a crop spraying event as claimed in any one of claims 10 to 14 in which the sensor units further comprise a compound detection unit and the method comprises the step of the sensor units determining the type of compound being sprayed on the crop during the spraying event.A method of detecting a crop spraying event as claimed in any one of claims 10 to 15 in which the sensor units further comprise means to determine the amount of compound being sprayed on the crop during the spraying event and the method comprises the step of determining the amount of compound being sprayed on the crop during the spraying event.A method of detecting a crop spraying event as claimed in any one of claims 10 to 16 in which the method comprises the initial step of distributing the sensor units remotely from each other in a field containing the crop.A method of detecting a crop spraying event as claimed in any one of claims 10 to 17 in which there is provided a cloud based remote memory and the method comprises the step of storing one or more of a crop spraying event, a crop spraying report and a crop spraying history in the cloud based remote memory.