The Effect of Weather Fronts on GPS Measurements

On the southeast coast of England, not very far from where the Battle of Hastings occurred, lies Herstmonceux Castle — a fifteenthcentury manor house that was, for many years, the home of the Royal Greenwich Observatory (RGO). Although the skies above the castle are generally clearer than those above RGO’s original home in the London borough of Greenwich, the frequently cloudy and rainy conditions are less than ideal for astronomy. RGO, therefore, built new telescopes on La Palma in the Canary Islands and moved most of its administrative and research facilities to Cambridge in 1990. The same poor conditions dreaded by astronomers, however, are ideal for studying weather fronts in relation to GPS. The grounds of Herstmonceux Castle (now owned by Canada’s Queen’s University and operated as an international study center) house an International GPS Service (IGS) station. This site has provided Drs. Thierry Gregorius and Geoffrey Blewitt with a wealth of data for their studies of the effects of weather fronts on GPS measurements, which they recount in this month’s column. Dr. Gregorius studied surveying at the Universities of Karlsruhe (Germany) and New South Wales (Australia), where he graduated with a B.E. in geomatic engineering in 1995. He then went to the United Kingdom to work on geophysical and meteorological applications of GPS at the University of Newcastle upon Tyne. After obtaining his Ph.D. this year, he moved to The Netherlands, where he now works for Shell International. of how atmospheric refraction maps into a GPS positioning error.