Development of topographic maps for precision farming with medium accuracyGPS receivers

The topographic map is considered by many to be an important base map for a precision farming GIS (Geographic Information system). Previous work has s own that dual-frequency survey grade GPS (Global Positioning System) receiv ers ae capable of producing accurate position data from a moving vehicle in a short time from which topographic maps can be developed. However, this t ype of GPS receiver is expensive and somewhat difficult to use properly. Th is article presents the results from using sub-meter horizontal accuracy GP S receivers to collect multiple passes of GPS data during normal field oper ations to develop topographic maps. the results sow that: (1) it is possibl e to develop a topographic map with a standard deviation of vertical error on the order of 10-12 cm with a sub-meter horizontal position accuracy GPS receiver, and (2) when data is collected under controlled GPS windows, a mi nimum of 10 passes of data with appropriate data processing is sufficient f or the development of topographic maps with sub-meter GPS receivers.