Prescription mapping for precision aerial application

Prescription Mappingfor Precision Aerial ApplicationPeng Song1,2; Yubin Lan2,*; Wei Li1; Xianfa Fang3;1College of Engineering, China Agricultural University, Beijing,China2USDA-ARS, College Station, TX, USA3Chinese Academy of Agricultural Mechanization Sciences, Beijing, China* Corresponding author.AbstractVariable-rate application (VRA) is one of the most important technologies in precision aerial application. Prescription maps instructthe controller how much product to apply based on the location of the field, which provide the basis for VRA. This paper discussedapproaches to convert mapping data such as soil data or NDVI data from remote sensing imagesinto application maps in various formats without much effort or special knowledge from the pilot/operator, which could then be a new service to customers. These application maps could then be easily uploaded into aspray system computer to make variable-rate aerial applications, such as cotton growth regulators, defoliants, and insecticides. With VRA technology, prescription maps have potential to benefit the industry by optimizingagriculturalproduction with reduced input usage and environmentalimpacts.Keywords:Precision aerial application, prescription maps, remote sensing, GPS/GIS, variable-rate aerialapplicationINTRODUCTIONAerial application, commonly called crop dusting, involves spraying crops with fertilizers,pesticides, and fungicides from an agricultural aircraft(Lan, et al., 2010). Aerial application can be used to treat large areas quickly; unlike ground spraying, it can treat in undulating terrain and wet soil conditions that prohibit the use of other forms of application, which enables the timing of spray treatments to be improved and soil compaction reduced. With a non-intrusive way, aerial application can also prevent damage to crops by spraying above canopy.As the development of precision agriculture, technologies such as global positioning system (GPS), geographic information systems (GIS), remote sensing and variable-rate application (VRA) allow farmers to manage field in a more effective way, which can optimize agriculture production with reduced input usage and environmental impacts(Moran, et al, 1997). Several studies have assessed the economic potential of variable rate application technology (Burton, et al., 1999).As one of the most important technologies in precision agriculture, variable-rate aerial application technology allows various rates of fertilizers, insecticides, herbicides, tillage and plant harvesting aids within the field at different zones(Thomson, et al., 2006;Kurt, et al., 2011;Cerri, et al., 2002). The process of a typical variable-rate aerial application system can be seen from Fig.1. Mapped data like soil sampling maps, soil type maps, or NDVI maps from remote sensing images, as well as historical records can be used to produce prescription maps for a specific area(Inman, et al., 2008). Studies worked on prescription map for its importance in VRA (Everitt, et al., 1996; Park, et al., 2005). It tells the controller how much product to apply at specific site. With a GPS receiver which locates theapplicator’s position on the map, the rate can be adjusted based on the prescription map as the aircraft fly over different zones of the field.Figure 1.Process of a typical VRAThe objective of this study wasto introduce the process of generating prescription maps with commercial software such as Farm Works software and how they ultimately fit into a complete precision application package.1. PRESCRIPTION MAPPINGA prescription map tells application controller how much product to apply based on the location in the field. Most agricultural GIS packages such as Farm Works Office from Trimble; EasiSuite from MapShots; SMS from Ag Leader and Apex from John Deere can create prescription maps in multiple formats(APEX, 2008; Farm Works, 2012; SMS, 2011). Following steps need to be followed to develop a prescription map for VRA: (1) perform VRA zones for the field; (2)develop a site-specific prescription map of the properties of interest; (3) use the prescription map to control a variable rate applicator(Grisso, et al.,2010;Dania, et al).1.1VRA ZoningFor prescriptions to be based on zones, developing management zones is essential for effective variable rate application. Three factors need to be considered to develop a zone map: (1)information to be used as a basis for creating zones; (2) procedure to process the information; (3) the optimal number of zones that a field should be divided into (Fridgen, et al.,2004).There are several methodsto delineate the zones.Zones can be created as required, such asbetween different crops, different fields or any other shapes and areas asdemands. Import roads, waterways data and satellite imagery as background images which show the outline of field and make it more accurately to draw zones boundary. Zones boundary can be easily edited later as required, and variable rate will be applied between different zones. The number of zones created depends on what we need. Figure 2 shows four zones built with Farm Works software.Variable rate will applied on different color areas after prescription map is produced.Figure2.Four zones for VRASoil type maps as well as any soil sampling maps can also be imported to create VRA maps on different zones. Visit from U.S. Department of Agriculture, Natural Resources Conservation Service for free U.S. soil data which can beused for zone delineation. A form of satellite imagery can be imported as a background to create boundaries,as can be seen from Figure 3.The soil survey data on Brazos County, Texas, wasrequired from U.S. Department of Agriculture, Natural Resources Conservation Service for analysis.Figure3.Import soil dataRemote sensing image is another approach to get VRA zones. Remote sensing is the process of gathering data from a distance. It developed with GPS, GIS and VRA technologies to assist farmers managing field in a more effective way, which can optimize agriculture production with reduced input usage and environmental impacts. Airborne remote sensing technology using agricultural aircrafts to collect images and data, has the advantage of rapid image acquisition, and can achieve vary spatial resolutions at different flight altitudes (Qin, et al., 2003; Thomson, et al.,2005;Huang, et al.,2009; ).Remote sensing data and images can formulated to normalized difference vegetation index (NDVI), which indicates varying levels of particular parameters such as plants nutrient content, growth status, water content, soil parameters and yield. Zones in NDVI mapspresent different crop conditions for variable rate application. Prescription map can also be created from NDVI map.NDVI map is extracted from remote sensing image.The remote sensing image used here acquired by MS-4100 multi-spectral camera. Figure 4 is the image acquired for cotton field on September 20, 2007 at the height of 7000 feet(Lan, et al., 2009).Erdas software was used to get the area of interest (AOI) (Figure 5) and make a calibration on the image. The NDVI map of the AOI area(Figure 6) was used to create a prescription map.Figure 4.Remote sensing imageFigure 5.AOI imageFigure 6.NDVI map by ErdasImport calibrated AOI area image to Farm Works as background, the image shows the outline of field which make it easier and more accurately to draw the boundary. It is the white area applied for area variable plan.Prescription map can be created after NDVI map loaded into Farm Works software.1.2 Prescription Map Created by ZonesZones map can be used for numerous applications, such as variable rate fertilizer, plant growth regulators, cotton defoliants, and seeding rates. When zones are created, it’s easy to develop a prescription map. Add a new view for zones map to create grid or contour map. For grid sampling, the boundary is typically divided into 2.5 acre grids. Select the contour or grid view map created to create prescription maps, as can be seen from Figure 7.The prescription values into the cells correspond with the zone colors showing on the map.Figure7.Prescription maps created by Farm Works1.3 Prescription Map FilePrescription maps will be imported to variable-rate control systems to apply for variable-rate application. So a prescription map should be created in appropriate format to match with special VRA controller. Most agricultural GIS packages can create prescription maps in multiple formats. The prescription map file should be saved as correct format after being created. For example, Ag Leader PF3000 Pro requires the *.tgt prescription map format, Raven Viper can read the *.shp format, AG-NAV®2 supports both DXF and shapefile formats, but John Deere controllers require a boundary file of the field be included in addition to the prescription map. With an airplane, the controller will automatically change its rates based on those specified in the prescription map and the GPS position as the aircraft flow over different zones.2. AERIAL VRA CONTROL SYSTEMThere are many commercial variable-rate control systems available in the market. The Air IntelliStar™ developed by Hemisphere GPS, allows flying and spraying precise patterns at the proper time using variable rate flow control, The IntelliStarlightbar guidance system features a real-time graphic moving map display that provides superior visual guidance, including highbright for daytime and red mode for nighttime. The screen shows swaths sprayed, field boundaries, skips and overlaps, mark points and waypoints, background maps and can be connected to the Internet using a USB modem; The AG-NAV®2 (AG-NAV) is a DGPS navigation system designed by AG-NAV Inc. It provides the pilot with swath and directional guidance and other navigation information. It supports all spray patterns from simple back and forth to automatic center field split in various ways; The ACCU-RATE® controller developed by Trimble Inc., prescription map can be loaded into the EZ-Guide 500 system or the FmX integrated display with two built-in GPS receivers to automatically vary the rate using prescriptions; The WINGMANTM, an advanced aerial spray management system designed by ADAPCO, provides basic flight guidance, flight recording, obstacle awareness, flow rate, application totals and acres treated functions is based on ADAPCO's proprietary SkyTracker(TM) software. SkyTracker provides real-time aircraft tracking and instantaneous processing of weather data for spray system optimization and graphical data display. Installed on an aircraft, those control system will automatically apply for variable rate application based on the prescription map imported as the aircraft flow over the field.3. CONCLUSIONVariable-rate aerial application technology has the potential to benefit the industry by saving operators and farmers’ time and money. As an important factor of VRA, prescription map allows various rates of fertilizers, insecticides, defoliants, herbicides, tillage and plant harvesting aids within the field at different zones. Following steps are needed to develop a VRA prescription map: (1) perform VRA zones for the field; (2) develop a site-specific prescription map of the properties of interest; (3) use the prescription map to control a VR applicator. With commercial variable-rate control systems in the market, the prescription maps could be easily uploaded into the controller to makevariable-rate aerial application.REFERENCES[1] Lan, Y. B., Huang, Y., &Marting, D. E.,et al. (2009). Development of an airborne remote sensing system for crop pestmanagement: system integration and verification. Applied Engineering in Agriculture. 25(4): 607-615.[2] Burton, C. 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