Wide-area agricultural monitoring and prediction
Ground-based measurements of agricultural metrics such as NDVI are used to calibrate wide-area aerial measurements of the same metrics. Calibrated wide-area data may then be used as an input to a field prescription processor.
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The disclosure is related to monitoring and prediction of agricultural performance over wide areas.
BACKGROUNDA modern crop farm may be thought of as a complex biochemical factory optimized to produce corn, wheat, soybeans or countless other products, as efficiently as possible. The days of planting in spring and waiting until fall harvest to assess results are long gone. Instead, today's best farmers try to use all available data to monitor and promote plant growth throughout a growing season. Farmers influence their crops through the application of fertilizers, growth regulators, harvest aids, herbicides and pesticides. Precise crop monitoring—to help decide quantity, location and timing of field applications—has a profound effect on cost, crop yield and pollution.
Normalized difference vegetative index (NDVI) is an example of a popular crop metric. NDVI is based on differences in optical reflectivity of plants and dirt at different wavelengths. Dirt reflects more visible (VIS) red light than near-infrared (NIR) light, while plants reflect more NIR than VIS. Chlorophyll in plants is a strong absorber of visible red light; hence, plants'characteristic green color.
where r is reflectivity measured at the wavelength indicated by the subscript. Typically, NIR is around 770 nm while VIS is around 660 nm. In various agricultural applications, NDVI correlates well with biomass, plant height, nitrogen content or frost damage.
Farmers use NDVI measurements to decide when and how much fertilizer to apply. Early in a growing season it may be hard to gauge how much fertilizer plants will need over the course of their growth. Too late in the season, the opportunity to supply missing nutrients may be lost. Thus the more measurements are available during a season, the better.
A crop's yield potential is the best yield obtainable for a particular plant type in a particular field and climate. Farmers often apply a high dose of fertilizer, e.g. nitrogen, to a small part of a field, the so-called “N-rich strip”. This area has enough nitrogen to ensure that nitrogen deficiency does not retard plant growth. NDVI measurements on plants in other parts of the field are compared with those from the N-rich strip to see if more nitrogen is needed to help the field keep up with the strip.
The consequences of applying either too much or too little nitrogen to a field can be severe. With too little nitrogen the crop may not achieve its potential and profit may be left “on the table.” Too much nitrogen, on the other hand, wastes money and may cause unnecessary pollution during rain runoff. Given imperfect information, farmers tend to over apply fertilizer to avoid the risk of an underperforming crop. Thus, more precise and accurate plant growth measurements save farmers money and prevent pollution by reducing the need for over application.
NDVI measurements may be obtained from various sensor platforms, each with inherent strengths and weaknesses. Satellite or aerial imaging can quickly generate NDVI maps that cover wide areas. However, satellites depend on the sun to illuminate their subjects and the sun is rarely, if ever, directly overhead a field when a satellite acquires an image. Satellite imagery is also affected by atmospheric phenomena such as clouds and haze. These effects lead to an unknown bias or offset in NDVI readings obtained by satellites or airplanes. Relative measurements within an image are useful, but comparisons between images, especially those taken under different conditions or at different times, may not be meaningful.
Local NDVI measurements may be obtained with ground based systems such as the Trimble Navigation “GreenSeeker”. A GreenSeeker is an active sensor system that has its own light source that is scanned approximately one meter away from plant canopy. The light source is modulated to eliminate interference from ambient light. Visible and near-infrared reflectivity are measured from illumination that is scanned over a field. Ground-based sensors like the GreenSeeker can be mounted on tractors, spray booms or center-pivot irrigation booms to scan an entire field. (GreenSeekers and other ground-based sensors may also be hand-held and, optionally, used with portable positioning and data collection devices such as laptop computers, portable digital assistants, smart phones or dedicated data controllers.) Active, ground-based sensors provide absolute measurements that may be compared with other measurements obtained at different times, day or night. It does take time, however, to scan the sensors over fields of interest.
What is needed are wide area plant monitoring systems and methods capable of providing absolute data that can be compared with other data obtained by different methods and/or at different times. Furthermore, farmers need help navigating the vast stores of potentially valuable data that affect plant growth.
Wide-area agricultural monitoring and prediction encompasses systems and methods to generate calibrated estimates of plant growth and corresponding field prescriptions. Data from ground and satellite based sensors are combined to obtain absolute, calibrated plant metrics, such as NDVI, over wide areas. Further inputs, such as soil, crop characteristics and climate data, are stored in a database. A processor uses the measured plant metrics and database information to create customized field prescription maps that show where, when and how much fertilizer, pesticide or other treatment should be applied to a field to maximize crop yield.
Ground data are used to remove the unknown bias or offset of satellite or aerial images thereby allowing images taken at different times to be compared with each other or calibrated to an absolute value. Soil, crop and climate data may also be stored as images or maps. The volume of data stored in the database can be quite large depending on the area of land covered and the spatial resolution. Simulations of plant growth may be run with plant and climate models to build scenarios such that a farmer can predict not just what may happen to his crops based on average assumptions, but also probabilities for outlying events.
A basic ingredient of any field prescription, however, is an accurate map of actual plant progress measured in the field. NDVI is used here as a preferred example of a metric for measuring plant growth; however, other parameters, such as the green vegetation index, or other reflectance-based vegetative indices, may also be useful.
In
Scale 305 in
It is apparent that NDVI measurements for the set of fields shown in
Soil data 415, crop data 420 and climate data 425 may also be inputs to the database and processor although not all of these data may be needed for every application. All of the data sources 405 through 425, and other data not shown, are georeferenced. Each data point (soil type, crop type, climate history, NDVI from various sources, etc.) is associated with a location specified in latitude and longitude or any other convenient mapping coordinate system. The various data may be supplied at different spatial resolution. Climate data, for example, is likely to have lower spatial resolution than soil type.
Data inputs 405 through 425 are familiar to agronomists as inputs to plant yield potential algorithms. Database and processor 430 are thus capable of generating wide-area field prescriptions based on any of several possible plant models and algorithms. The ability to run different hypothetical scenarios offers farmers a powerful tool to assess the risks and rewards of various fertilizer or pesticide application strategies. For example, a farmer might simulate the progress of one of his fields given rainfall and growing degree day scenarios representing average growing conditions and also growing conditions likely to occur only once every ten years. Furthermore, the farmer may send a ground-based NDVI sensor to scan small parts of just a few of his fields frequently, perhaps once a week, for example. These small data collection areas may then be used to calibrate satellite data covering a large farm. The resulting calibrated data provides the farmer with more precise estimates of future chemical needs and reduces crop yield uncertainty.
It is rarely possible to obtain ground and satellite NDVI data measured at the same time. If only a few days separate the measurements, the resulting errors may be small enough to ignore. However, better results may be obtained by using a plant growth model to propagate data forward or backward in time as needed to compare asynchronous sources.
In
The use of a linear plant growth model to compare asynchronous ground-based and satellite measurements of NDVI may be understood by referring to
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It will be apparent to those skilled in the art that the methods discussed above in connection with
Sparse spatial NDVI sampling may be sufficient to calibrate wide-area satellite data. More dense sampling is needed for smaller management zones which are often associated with more rapidly varying topography, while less dense sampling is sufficient for larger management zones which are often associated with flatter topography.
The wide-area agricultural and prediction systems and methods described herein give farmers more precise and accurate crop information over wider areas than previously possible. This information may be combined with soil, climate, crop and other spatial data to generate field prescriptions using standard or customized algorithms.
Although many of the systems and methods have been described in terms of fertilizer application, the same principles apply to pesticide, herbicide and growth regulator application as well. Although many of the systems and methods have been described as using images obtained from satellites, the same principles apply to images obtained from airplanes, helicopters, balloons, unmanned aerial vehicles (UAVs) and other aerial platforms. Thus “aerial data” comprises data obtained from satellite, airplane, helicopter, balloon and UAV imaging platforms. Similarly, “ground-based data” comprises data obtained from sensors that may be mounted on a truck, tractor or other vehicle, or that may be hand-held. Although many of the systems and methods have been described in terms of NDVI, other reflectance-based vegetative indices may be used.
The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the principles defined herein may be applied to other embodiments without departing from the scope of the disclosure. Thus, the disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for calibrating agricultural measurements comprising:
- obtaining aerial data representing relative measurements of an agricultural metric in a geographic area, the relative measurements having an unknown bias;
- obtaining ground-based data representing absolute measurements of the agricultural metric within the geographic area; and,
- using the absolute measurements to calibrate the relative measurements, thereby synthesizing absolute measurements of the agricultural metric in parts of the geographic area.
2. The method of claim 1, the aerial data obtained from a satellite.
3. The method of claim 1, the aerial data obtained from an airplane.
4. The method of claim 1, the agricultural metric being normalized difference vegetative index.
5. The method of claim 1, the agricultural metric being a reflectance-based vegetative index.
6. The method of claim 1 further comprising: combining data representing the ground-based and synthesized absolute measurements with additional spatial agricultural data to generate a prescription for the application of chemicals to an agricultural field.
7. The method of claim 6, the additional spatial agricultural data being a soil data map.
8. The method of claim 6, the additional spatial agricultural data being a crop data map.
9. The method of claim 6, the additional spatial agricultural data being climate data.
10. The method of claim 6, the chemicals being fertilizers.
11. The method of claim 6, the chemicals being pesticides or herbicides.
12. The method of claim 6, the prescription based on an agricultural algorithm having an agricultural metric and climate data as inputs.
13. The method of claim 12, the agricultural metric being normalized difference vegetative index and the climate data including growing degree days since planting.
14. The method of claim 1, the synthesizing absolute measurements including using a plant growth model to propagate ground-based data forward or backward in time as needed to compare it with non-contemporaneous satellite data.
15. The method of claim 14, the plant growth model being a linear model.
16. A system for making calibrate agricultural measurements comprising:
- a source of aerial data representing relative measurements of an agricultural metric in a geographic area, the relative measurements having an unknown bias;
- a source of ground-based data representing absolute measurements of the agricultural metric within the geographic area; and,
- a database and processor that use the absolute measurements to calibrate the relative measurements, thereby synthesizing absolute measurements of the agricultural metric in parts of the geographic area.
17. The system of claim 16, the aerial data obtained from a satellite.
18. The system of claim 16, the aerial data obtained from an airplane.
19. The system of claim 16, the agricultural metric being normalized difference vegetative index.
20. The system of claim 16, the agricultural metric being a reflectance-based vegetative index.
21. The system of claim 16, the database and processor further combining data representing the ground-based and synthesized absolute measurements with additional spatial agricultural data to generate a prescription for the application of chemicals to an agricultural field.
22. The system of claim 16, the additional spatial agricultural data being a soil data map.
23. The system of claim 15, the additional spatial agricultural data being a crop data map.
24. The system of claim 16, the additional spatial agricultural data being climate data.
25. The system of claim 16, the chemicals being fertilizers.
26. The system of claim 16, the chemicals being pesticides or herbicides.
27. The system of claim 16, the prescription based on an agricultural algorithm having an agricultural metric and climate data as inputs.
28. The system of claim 27, the agricultural metric being normalized difference vegetative index and the climate data including growing degree days since planting.
29. The system of claim 16, the synthesizing absolute measurements including using a plant growth model to propagate ground-based data forward or backward in time as needed to compare it with non-contemporaneous satellite data.
30. The system of claim 16, the plant growth model being a linear model.
Type: Application
Filed: Oct 25, 2010
Publication Date: Apr 26, 2012
Applicant: Trimble Navigation Limited (Sunnyvale, CA)
Inventors: Robert J. Lindores (Boulder, CO), Ted E. Mayfield (Ukiah, CA), Morrison Ulman (Mountain View, CA)
Application Number: 12/911,046
International Classification: G06F 17/10 (20060101); G06F 19/00 (20110101);