USMA Research Unit Affiliation

Geography and Environmental Engineering

Date of Award


Document Type

Master's Thesis

Degree Type

Master of Science (MS)


This report provides a study of the statistical data extracted from the United Kingdom’s National Global Positioning System (GPS) Network, specifically Station SCP1 at St. Catherine’s Point Lighthouse on the Isle of Wight. The entire network consists of 30 continuously operating GPS reference stations located throughout Great Britain. These stations are permanently installed, precisely coordinated active GPS stations. The station at Saint Catherine’s Point on the Isle of Wight appears to have shifted from its original position. This was attributed to the extensive rainfall in the autumn and winter of 2000, which could have caused soil erosion at the base of the lighthouse. This perceived movement has impacted the initial coordinates of the site.

The receivers used in the network are designed to provide users with their relative location to within a few centimetres. All stations record dual-frequency GPS data 24 hours a day at a 15 second epoch rate. The receiver at Saint Catherine’s Point (SCP1), a Trimble 4000 SSI with a Model 33429.00 antenna, is affixed upon a lighthouse. Between September 2000 and March 2001 the lighthouse moved in a southern direction and produced GPS residuals outside of the accepted 95% confidence level. There is a strong correlation between the amount of rainfall experienced at Saint Catherine’s Point and the rate of change of movement south of the lighthouse.

The results are based upon the GPS data provided by the Ordnance Survey and the data gathered in the field by the author. The analysis indicates St. Catherine’s Lighthouse has moved approximately 10 centimetres south over the past seven months. A future cumulative rainfall total equivalent to that of the autumn of 2000 could potentially produce an additional southward shift of 2 centimetres.