GPS and Precision Agriculture GPS Global Positioning System

GPS and Precision Agriculture

GPS – Global Positioning System Three Parts Space Segment 24 active and 3 spare satellites orbiting the Earth Orbital patterns and spacing of satellites provide 9 -12 satellites above the horizon at any point on the Earth. This allows for each point of the Earth’s surface to have a unique address. User Segment GPS receivers and the user community Control Segment 5 monitoring stations around the world Master control facility at Falcon Air Force Base in Colorado Time and distance of signals determine location 4 Satellites needed for receiver to get accurate location.

GPS Cool Facts First GPS satellite was launched in 1978. Dept. of Defense declared GPS fully operational in 1995. 24 Satellites in orbit at this moment. Cost estimated $12 billion to build & launch. Each satellite weighs about 1, 735 pounds. Satellites orbit about 12, 500 miles above the Earth. Satellites take 12 hours to orbit the Earth once. Russians have a system identical to U. S. system called GLONASS.

GPS Signals and Corrections Atmospheric and equipment conditions can cause errors in accuracy. The receiver, using mathematics and modeling can correct errors. In agricultural applications, the most common way to counteract GPS errors is by using Differential GPS, or DGPS. A base station is place at an accurately known location. Base station receiver will calculate the error between the actual location and the location computed from GPS signals. Improved version is Kinematic DGPS, or Real Time Kinematic (RTK) GPS. Available by subscription.

Differential GPS

Agricultural Applications of GPS Guidance Systems Planting Spraying Spreader/applicators Tillage Harvesting Mapping yields (GPS + combine yield monitor) Variable Rate Technology

Guidance Systems 2 Types of Systems Lightbar or Parallel Tracking Operator still drives and steers the machine. Lightbar provides feedback on proper positioning reference. Autoguidance or Auto. Steer Machine drives itself Operator only turns machine around, then lines up on next pass before engaging.

Variable Rate Technology (VRT) Any technology that enables the Variable Rate Application (VRA) or agricultural inputs Technology which permits precise application control of inputs. Fertilizer Pesticides Lime Seeding Tillage Irrigation

Map-based VRT Prescription Maps DGPS Prescription Map Controller Applicator Output

Benefits of VRT Economics Increased input efficiency – apply only what is needed. Could reduce overall amounts of inputs used. Improved in-field equipment efficiency. Improved crop yields through optimal input use. Environmental Stewardship Minimize over-application of inputs thereby reducing the risk of pesticide and fertilizer runoff or leaching into water sources. Reduce application in environmentally sensitive areas.

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