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

2. 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.

3. Selecting GPS Components
Hand Held
Backpack
Vehicle Mounted
Recreational
Mapping
Surveying

4. GPS/GIS Applications Guidance Control Mapping 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

5. 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
10 cm
5 cm

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

7. 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.

8. 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.

9. 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

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

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

12. Semi-Automatic Soil Sampler

13. Crop Maze
Field Boundary,
Vollmer Farm, Bunn, NC

14. Crop Maze

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

16. 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.

17. Cotton Yield Map

18. 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

19. Weed Map

20. 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

21. Prescription Map

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