Role of optimum satellite-receiver geometry in the accuracy of GPS Navigation solution - an investigation

The field of Civil Aviation sector in India is going to be revolutionized by the Indian Regional Navigation Satellite System, which is regional navigation system of the Indian sub-continent. The accuracy of the Navigation solution of any satellite based navigation system is affected by several factors such as delay due to refraction in atmospheric layers, clock drift errors, errors due to multipath and satellite-receiver geometry. The navigation solution accuracy of any regional navigation system can be improved by augmenting the regional system with a Global satellite based Navigation system such as Global Positioning System, which is the popular and completely operational Global Navigation Satellite System In order to augment the IRNSS with GPS, initially it is necessary to investigate the techniques to improve the navigation solution accuracy of the GPS. Even though the delay errors due to atmospheric layers and multipath are mitigated, the accuracy of the GPS navigation solution is affected by satellite-receiver geometry, which represents the geometrical locations of the Navigation satellites seen by the GNSS receiver. As the satellite-receiver geometry is measured by Geometric Dilution of Precision (GDOP), monitoring of GDOP is necessary to determine the navigation solution accuracy. In this paper, the dual frequency GPS receiver data of the IGS Station, NGRI, Hyderabad (Lat./Long: 17.407430/78.526620) is collected using the SOPAC to carry out the required investigation of the navigation solution accuracy with DOP, by selecting four optimum satellites. This work can be extended by considering the IRNSS satellite positions along with GPS satellite locations.