GPS provides accurate location information at any point on or near the earth’s surface by calculating your distance from at least three orbiting satellites at once. So farming machines with GPS receivers are able to recognize their position within a farm field and adjust operation to maximize productivity or efficiency at that location.
Take the example of soil fertility. The farmer uses a GPS receiver to locate preselected field positions to collect soil samples. Then a lab analyzes the samples, and creates a fertility map in a geographic information system. That’s essentially a computer database program adept at dealing with geographic data and mapping. Using the map, a farmer can then prescribe the amount of fertilizer for each field location that was sampled. Variable-rate technology (VRT) fertilizer applicators dispense just exactly the amount required across the field. This process is an example of what’s come to be known as precision agriculture.