Evaluation of Sub-Meter and 2 to 5 Meter Accuracy GPS Receivers to Develop Digital Elevation Models

The digital elevation model (DEM) is considered by many to be an important base map for a precision farming GIS (Geographic Information System). Previous work has shown that dual-frequency survey grade GPS (Global Positioning System) receivers are capable of rapidly producing accurate positional data from a moving vehicle from which DEM's can be developed. However, this type of GPS receiver is expensive and somewhat difficult to use properly. This paper presents the results of a study to evaluate the potential of using single frequency sub-meter and 2–5 meter horizontal accuracy GPS receivers to enable the farmer to collect multiple passes of GPS data during normal field operations from which DEM's can be developed. The results show that when using a single frequency sub-meter GPS receiver: (1) it is possible to develop a DEM with standard deviation of the elevation accuracy on the order of 0.12–0.14 m, (2) in order to collect data with this level of elevation accuracy, data should only be collected when the GDOP (Geometric Dilution Of Precision) is less than 5.0, (3) at least 10 passes of data with appropriate data averaging is required to produce this level of elevation accuracy. The results also indicate that the vertical error associated with a 2–5 meter horizontal accuracy GPS receiver is such that it is not recommended for use in collecting data to develop DEM's in this application.