Comparison of Methods for Obtaining Absolute WGS 84 Position in Remote Locations

John Brown, M. Elizabeth Cannon, Douglas Roberts, James G. Morgan

Abstract:	In June of 1993, Chevron Overseas Petroleum Inc. and the government of Kazakhstan signed an agreement to further develop the Tengiz and Korolev Oil Fields located on the northeast end of the Caspian Sea. The new joint-venture company, Tengizchevroil (TCO), teamed with Chevron Petroleum Technology Company (CPTC) to place a 29 point control network in the region which would serve as the reference base for all mapping and positioning projects. To obtain estimates of absolute position in the WGS 84 system while in the field, the CPIC/TCO group used one dual frequency GPS receiver operating in single point positioning mode, processed the data with the broadcast ephemeris, and performed a least squares adjustment on the network with the WGS 84 absolute positions weighted according to a scheme using the difference between the single point position and a later measured single frequency baseline. Upon returning to the United States, precise ephemeris files were obtained and the GPS observation data were reprocessed by the Defense Mapping Agency and by CPTC using commercial software. In 1994, the data were reprocessed using SPARC, the single point and differential positioning software developed by the Geodetic Survey Division of Geomatics Canada - Natural Resources. Selective Availability (SA) was implemented during the entire data collection period and Anti- Spoofing during 2 of the 6 days of dual-frequency data collection. The methodology and results from all techniques are explained and compared. Minor differences at the 3 meter level are found in the horizontal components and larger differences near 10m to 15 m are encountered in the vertical. Explanations as to why this occurred are offered as well as suggestions for performing this type of work in the future.
Published in:	Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994) September 20 - 23, 1994 Salt Palace Convention Center Salt Lake City, UT
Pages:	51 - 60
Cite this article:	Brown, John, Cannon, M. Elizabeth, Roberts, Douglas, Morgan, James G., "Comparison of Methods for Obtaining Absolute WGS 84 Position in Remote Locations," Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994), Salt Lake City, UT, September 1994, pp. 51-60.
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