The Tuolumne County GPS Network was constructed by Condor Earth Technologies
under contract to Tuolumne County. The project was carried out under the auspices
of the CSRC and was submitted to NGS in January, 2003.
In January 2004 the project was published by NGS as a Height Modernization survey
meeting the 2 centimeter accuracy specifications for GPS-derived orthometric heights.
The horizontal accuracy of the entire network has been classified by NGS as Order B
(minimum accuracy of 1 part per million). The final NGS adjustment of the network
matched the CSRC adjustment at sub-millimeter agreement horizontally, with a mean
difference in adjusted orthometric heights of less than 2 millimeters.
The Tuolumne County GPS Network consists of 58 control stations, 12 of them Primary Control,
2 Secondary Control, and the remainder "Network" Control. The network extends from point
U956 in the west, in California's Central Valley with an elevation of only 39+ meters
above sea level, extending to the east to the crest of the Sierra Nevada and beyond to
X 123 on the eastern slope of the Sierras, with the highest elevation being 2912 meters
1 mile east of Tioga Pass along Route 120 in Yosemite National Park. The network encompasses
about 6000 square miles.
The collaboration between NGS and CSRC on this project was a primary ingredient in the
development of NGS' most recent geoid model, GEOID03.
Contributed by: Mike Potterfield