Adverse effects of receiver clock bias and drift on NavIC user position coordinates and their mitigation

Highlights

• For evaluating the performance of the NavIC receiver, ISRO has installed several NavIC receivers all over India for field trials. One such receiver was installed at our institution.

• The effect of clock bias and drift on NavIC receiver position coordinates and its mitigation technique are presented.

• We found periodic abnormal behaviour in X, Y, Z position coordinates every day for a certain duration of time. It is quite possible that many researchers might have attributed this to various reasons or might have taken them as real values.

• We found it is due to receiver clock bias and drift and also developed a mitigation technique based on low pass Butterworth filter.

• Results findings in this paper would be helpful not only to the researcher working on NavIC receivers but also other researchers working on GNSS receivers facing similar problems.

Abstract

We investigated the effects of receiver clock bias and drift on NavIC receiver position coordinates at a low latitude station and proposed a mitigation technique. For this, Five weeks data of Accord IRNSS-GPS-SPS (AIGS) receiver are considered. Error in each position coordinates (X, Y and Z) is estimated and observed that the maximum error occurred in user position Z-coordinate. CEP for 2D position is analyzed and observed that the Circular Error Probability (CEP) values are high in Z coordinate of YZ and ZX planes. Further, it is noticed that the timing of sudden enhancement of both clock bias and drift parameters coincides with the periodic anomaly of the X, Y and Z coordinates. The error in individual position coordinates is minimized by applying 6th order Butterworth low pass filter resulting in improved position accuracy. If such errors are not mitigated, the position estimation of the receiver becomes highly erroneous.