Smoothing Filters With Extended Kalman Filter In Single Frequency IRNSS Receiver For High Position Accuracy

Abstract

The IRNSS receiver uses the trilateration technique to compute receiver position coordinates, which requires the receiver to determine the range between the user and at least four satellites. To obtain very precise location coordinates, the receiver requires an accurate assessment of range; this range between the user and the location of the satellite is known as "pseudorange," since the receiver calculates range with some delays. The code phase or the carrier phase can be used to calculate pseudorange. The receiver can also calculate pseudorange utilising both code and carrier phase measurement since pseudorange based on carrier phase is very accurate but has integer ambiguity and pseudorange based on Code phase is not so accurate but has no ambiguity. In this paper we propose the use of Hatch filter and Kalman filter as smoothing filters for Smoothed Pseudorange to overcome the integer ambiguity problem along with Extended Kalman Filter to solve nonlinear equations which is modified version of Least Square Method. The proposed method shows highly accurate position coordinates with a high convergence rate in fixed antenna mode thereby the position accuracy improves from 20 meter to 5-7 meter for the Single Frequency IRNSS Receiver.