Establishment of a 3-dimensional geodetic network using the MACROMETER II^tm dual-band surveyor

Summary

During July of 1985, Aero Service conducted aGPS research project over a900 square km area in the Sacramento Valley of California. The project was partially funded by the California Department of Water Resources and was coordinated with the Sacramento office of U.S.G.S. The survey was designed to evaluate the accuracy, efficiency, and reliability ofMACROMETER II technology, as an alternative to conventional leveling techniques, for the monitoring of land subsidence.

Thirty independent baseline vectors were determined between21 pre-existing benchmark locations. The majority of baseline vectors measured approximately10 km in length and were observed in a highly productive mode of three,1-hour observations per day. Six baseline vectors ranging from34 to56 km in length were observed as single day, 3.5 hour observations. In all cases the integer values ofL ₁ andL ₂ double-differenced phase biases were determined. The relative positions of stations in the network were determined to within1 part per million(1 ppm) in both horizontal coordinates, and about1.6 ppm in the vertical.

Operational aspects of the project are described. Project results are examined with emphasis on the added benefits of dual-frequency measurements; the repeatability of interferometric determinations of individual baseline vectors; and the three-dimensional vector closure of the networks as a whole.