A Comparison of Rapid GPS Techniques for Development of Topographic Maps for Precision Farming

Rex L. Clark and Rusty Lee

Abstract:	Dual frequency carrier phase GPS receivers were used to examine the feasibility of using GPS, particularly kinematic modes on moving vehicles, to develop topographic maps. Two GPS data collection modes were used, stop & go (using a tripod GPS antenna mount) and kinematic (with tractor mounted GPS antenna). The first kinematic study used post processed differential corrections; the second kinematic study used real time differential corrections. It was found that the standard deviation of the elevation error between 10 true error points and the calculated topographic surface ranged from 2-3 cm for data collected on an approximate 3 m grid. The error for derived grid spacings of 9, 18, and 33 m ranged from 2-5 cm. A comparison of contour lines for the field between the 3, 9, 18, and 33 m grid spacings showed minor contour error, except in the flat sections of the field. The time required to collect and process the data using the kinematic mode was about l/l0 of the time required with the stop & go mode. The kinematic study with real time differential corrections revealed several important advantages and disadvantages, which are discussed in the paper. From these initial results it appears that kinematic GPS can be a viable technology for the rapid development of highly accurate topographic maps. The GPS hardware and software must have the ability to resolve the ambiguities on the carrier phase signal, and the field must be relatively clear of trees and other potential physical obstructions to the GPS signals.
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	495 - 504
Cite this article:	Clark, Rex L., Lee, Rusty, "A Comparison of Rapid GPS Techniques for Development of Topographic Maps for Precision Farming," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 495-504.
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