Map surfaces, on the other hand, treat a field as a continuous surface by partitioning it into thousands of grid cells that track gradual transitions throughout the field. Each grid-cell in a map layer contains a value indicating the condition at that location. The procedure is repeated for all of the locations resulting in a prescription map. The result is doing the right thing, in the right way, at the right place and time. The introduction of map surfaces takes precision farming beyond traditional thematic mapping and geoquery.
Data mining involves analysis of the spatial relationships among a set of maps.
For example, a map of yield variations for a field can be compared to the conditions, such as soil properties, nutrient levels and terrain configuration. A GIS can be used to set up and evaluate farm trials. Figure 2 illustrates a strip trial to determine the best seed hybrid for a field. A whole-field test compares the yield values of the two groups to see if they are statistically different. Areas of unusual conditions, such as high nematode activity or bottomlands, can be easily partitioned and tested for differences under these conditions.