Signal emission time effect on orbital and navigation solutions for precise applications

Abstract

Time is a fundamental part of position estimation and Global Positioning System (GPS) works on time measurements between known position and unknown position. So far most of the research was on modelling the propagation path delays, pseudorange correction, instrument bias errors and integer ambiguity resolution. But not much research is dedicated to model onboard clock correction and the impact of relativistic error (due to eccentricity) on signal emission time. These errors not only degrade the satellite position accuracy but also manifest as large pseudorange error when it is scaled by speed of light, which in turn degrade the receiver position accuracy. In this paper the signal emission time from satellite antenna phase center is modelled by considering the clock correction parameters, signal reception time at the receiver and relativistic error. The impact of satellite clock error and relativistic error on satellite position and receiver position are estimated and analysed. This precise timekeeping will improve the accuracy of the satellite position, which minimise the error in pseudorange and in turn receiver position accuracy is enhanced. This research work will be useful for GPS augmented systems like GAGAN(GPS Aided GEO Augmented Navigation) and WAAS(Wide Area Augmentation System).