Ground-Based GPS Sensing of Azimuthal Variations in Precipitable Water Vapor

Current models for troposphere delay employed by GPS software packages map the total zenith delay to the line-of-sight delay of the individual satellite-receiver link under the assumption of azimuthal homogeneity. This could be a poor approximation for many sites, in particular, those located at an ocean front or next to a mountain range. We have modified the GIPSY-OASIS II software package to include a simple non-symmetric mapping function (MacMillan, 1995) which introduces two new parameters.