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Contents under development - updated July 24, 2003
 

Towards Development of an Ultra High Resolution ( 1 cm) Local Gravimetric Geoid Model For The Reno-Tahoe Region

 Gary Oppliger
  Arthur Brant Laboratory for Exploration Geophysics, University of Nevada, Reno.

The GPS and InSAR methods are now widely applied to detect natural and man induced  changes in surface elevations of economic importance that may be less than one centimeter per year. These methods offer a possible way to extend and replace the traditional optical sprit leveling in many applications, but the successful union of the traditional and new methods requires that local sub-centimeter accuracy geoid models be available.  Currently the best available geoid model for the USA offers only 5 cm RMS absolute accuracy. (NGS Geoid99). At local scales it is though to be as accurate as 2 cm RMS, but the actual accuracy levels are also subject to local crustal density and gravity variations that were not available for input to the model.       

This project will examine and evaluate a new computational protocol for developing and maintaining local gravimetric geoid models.  The method promises higher spatial resolution independent of local elevation and an improved facility for revision as new gravity control  becomes available. 

The Reno-Tahoe study region offers elevation, density and gravity field extremes that make it  well suited for evaluating the effectives of new local geoid computation methods. The region is characterized by  1) abrupt topographic elevation changes exceeding 1500m meters in 10 km, 2) a minimum base elevation of 1400 meters (which can challenge methods condense terrain mass on to geoid) 3) 10 -20 mgal CBA variations over 20 km are common.  The work also takes advantage of new gravity coverage in the Reno-Tahoe Region.

 NGS Geoid99 Model  5 cm contours

Description of Method (link)