Comparison Between Differential GPS and On-The-Fly Real Time Kinematic for Land Seismic Stake Out

Both Differential GPS (DGPS) and On-The-Fly Real TIme Kinematic (OTF RTK) are being used by land seismic surveyors for stake out operations. The objective of this study is to compare the two technologies under actual field conditions. Field evaluations were conducted on two occasions in 1994 in BraziI. In both tests conventional survey techniques were used to establish survey truth. Trimble 4000 SSE OPS receivers capable of both DGPS and OTF RTK operations along with TrimMark data links were used. The results show that both DGPS and OTF RTK yield satisfactory submeter performance for the horizontal accuracy. The vertical accuracy for DGPS is affected by multipath errors with the accuracy usually being within 1 - 2 meters. There were some errors as large as 4 meters. The vertical error for OTF RTK was at the few centimeter level and the worst case error was less than two decimeters. If most of the time" vertical accuracy of 1 - 2 meters is satisfactory then DGPS is a good solution. If "all the time" sub-meter vertical is the requirement then OTF RTK is the answer. The seismic surveyor does not need the centimeter accuracy of OTF RTK but rather the quality assurance that the errors, especially in the vertical, are constrained to some low level.