GPS Applications in Agriculture. Gary T. Roberson Agricultural Machinery Systems

Transcription

1 GPS Applications in Agriculture Gary T. Roberson Agricultural Machinery Systems

2 What is a Positioning System? A position information system enables the user to determine absolute or relative location of a feature on or above the earth s surface. Position data is reported in georeferenced format. Latitude-longitude State plane UTM

3 Position Information System Requirements Provide position data with acceptable degree of accuracy. Must be available on demand at any time. Must be available at any location. Must be able to interface with other equipment.

4 Types of Position Information Systems Dead Reckoning Laser Systems Global Navigation Satellite System (GNSS) Global Positioning System (GPS) - US GLONASS - Russia Galileo - Europe

5 Global Positioning System (GPS) Space and land based information system to determine precise position data. Utilizes military satellites to determine positioning information. Position based on trilateration from know satelite locations. Millions of GPS users worldwide. Most common type of system in agriculture.

6 Selecting GPS Components Hand Held Backpack Vehicle Mounted Recreational Mapping Surveying

7 Selecting GPS Components Real Time Vs. Post Processed Do you need to know where you are right now? Number of Channels More channels means better selection of satellites. Differential Correction Method to improve position accuracy

8 Parts of a Complete System Antennae Receiver Display Storage Interface

9 GPS Antenna Antennae come in many shapes and sizes Basic function... receive the GPS Signal Position data is interpreted based on antenna location

10 GPS Receivers Many different types GPS - uncorrected data needing post processed for atmospheric interferences Differential GPS - signal is corrected as data is acquired, requires an additional satellite or second receiver Basic function... decode the signal retrieved by the antenna

11 GPS Display and Storage Records and reports GPS data to the user numerically graphically Can be integrated with the receiver or provided by handheld or laptop computer

12 Interfacing With Other Devices Proprietary Protocol Unique to Receiver Manufacturer Standardized Protocol Allows data exchange between many devices. NMEA 0183 ASCII code Consists of Data Sentences.

13 Communicating with other devices NMEA Protocol Baud Rate, data bits, parity Message definitions NMEA messages contain data for the connected device to record or interpret. Example GLL,xxxx.xx,a,yyyyy.yy,a,hhmmss.ss,A*hh Geographic Latitude Longitude, latitude.xx, n/s,longitude.yy,e/w,time,status

14 Type of GPS receivers for Agriculture Configuration GPS DGPS Beacon WAAS Satellite Subscription Dual Frequency GPS RTK GPS Accuracy 10 meters 1 meter (within range) 2 to 5 meters 1 meter 2 to 4 inches 1 to 2 inches

15 GPS Applications Guidance Point Guidance Swath Guidance Control Variable rate application Variable depth tillage Variable irrigation Mapping Soil properties Chemical Application Chemical Prescriptions Tillage Maps Yield Mapping Pest Mapping Topographic Maps Planting Maps

16 What Are Acceptable Accuracy Requirements? Variable fertilizer application (Swath control) Yield mapping Variable herbicide application Spray overlap control Row crop planting Seed bed formation 30 m 1 m 10 m 1 m 10 cm 10 cm 5 cm

17 Point Guidance Target point selected on map screen. Cursor location indicates present position, target position highlighted. Cursor provides guidance to target. Click to View Guidance Demo

18 Swath Guidance Anchor points established to create base line on map screen. Parallel lines generated at desired swath spacing. Can be used for straight or contour swaths Light bar or similar device used to provide guidance along line. Automatic steering possible. Swath Guidance Demo

19 Field Mapping Position data (georeference data) recorded at predetermined intervals. Other data recorded manually or automatically by monitor, computer, or data logger. Data displayed by geographic information system (GIS) in thematic map format.

20 Soil Sampling Georeferenced soil samples can be collected Sampling Methods Grid sampling: intensive sampling of entire field Directed sampling: intensive sampling of particular target areas

21 Grid Sampling Data collected for each cell or point Multiple samples combined into each cell or point sample

22 Directed Sampling Sampling zones established based on knowledge of field GPS used to locate sample points. Areas of interest intensely sampled, others lightly sampled

23 Semi-Automatic Soil Sampler

24 Crop Maze Field Boundary, Vollmer Farm, Bunn, NC

25 Crop Maze

26 Crop Maze 5 acre corn field Creative minds Sub meter DGPS Field computer Mapping software 450 foot tall wolf

27 Yield Maps Record of spatial yield variability within a field or farm. GPS data coupled with yield data to produce map. Mechanically harvested Hand harvested Useful tool for decision making.

28 Cotton Yield Map

29 Field Scouting Fields can be scouted for a variety of pests Pest populations recorded on maps Decision tools can be applied on a site specific basis

30 Weed Map

31 Variable Rate Control Application rates designed for needs of small sections of a field GPS determines position of equipment in the field Computer controls use GPS data and prescription files to adjust rate

32 Prescription Map

33 Summary GPS hardware and software are valuable management tools. Accuracy requirements should be dictated by task requirements. GPS hardware should be selected to be compatible with the complete system.