Neutral Atmospheric Refraction on Microwave Propagation and Its Implication on GPS Based Ranging System

Tropospheric refraction affects microwave propagation by retarding and bending, causes an error in microwave ranging. This limits the accuracy in satellite-based GPS navigation. This paper attempts to model tropospheric range error (∆RT) over Indian subcontinent (8oN-32oN) using mean model of atmosphere derived from Radiosonde data. A set of empirical relationships connecting surface atmospheric parameters with ∆RT (rather its zenith component, TZD) was established for different stations over the Indian subcontinent. The accuracy of these models in predicting the range errors are established by comparing the model estimates, with true ∆RT estimated through ray tracing. The models agree well with GPS measured TZD for all seasons within ±5cm