European Projects

1997 Northern Spain - Precise GPS/Gravity Survey

UGL was contracted to MWH GeoSurveys, Ltd. to provide GPS expertise on this precise gravity survey near Bilbao, Spain. Five Leica System 300 dual frequency receivers were utilized. Each gravity point was observed using the rapid static technique. Redundancy of measurement was built into the survey.

Post processing was done using Leica's Ski software. Single point solutions for each days basestation data was combined with the inter-base vectors to establish the project horizontal datum. As a number of the basestation locations were repeatedly reoccupied this resulted in WGS'84 locations which after 10 days would not change by more than 10 cm.

The vertical datum was established by tying to local first first order levelling benchmarks. Geoidal undulations were computed using the OSU91A geopotential model.

Final coordinates were computed in a least squares adjustment using RASCAL, a rigorous adjustment and statistical analysis package. Over 1,700 points were positioned.