Precise troposphere delay model for Egypt, as derived from radiosonde data

Tropospheric delay computation is necessary to improve GPS measurements accuracy. Precise determination of these propagation delays requires knowledge of the full refraction profile at signal path. In the present research, precise troposphere slant delay model (PTD) is derived based on ten stations of radiosonde data well-distributed over and around Egypt. To derive the PTD, the troposphere is divided into regular small layers. Ray tracing technique of actual signal path traveled in the troposphere is used to estimate tropospheric slant delay. Real GPS data of six stations in 8-day period were used for the assessment of zenith part of PTD model against the available international models. These international models include Saastamoinen, Hopfield, and the local Egyptian dry model proposed by Mousa & El-Fiky. The data were processed using Bernese software version 5.0. The closure error results indicate that the PTD model is the best model in all session, but when the available radiosonde stations are less, the accuracy of PTD model is near to classic models. As radiosonde data for all ten stations are not available every session, it is recommended to use one of the regularization techniques for database to overcome missing data and derive consistent tropospheric delay information