Effect of Sampling Rate Error on GNSS Velocity and Clock Drift Estimation

Abstract

A sampling frequency error in a GNSS receiver is shown to manifest as a scaling of a satellite's true Doppler shift, which cannot be properly accounted for by estimating a common clock drift across satellites, resulting in slowly varying biases in the receiver's velocity and clock drift estimates. For typical GNSS receivers whose oscillator frequency error is in the range of a few parts per million (ppm), the errors are negligible. However, for oscillators whose frequency error is several thousand ppm (e.g., for MEMS-based oscillators), or for applications with large Doppler shifts (e.g., space-borne receivers), the effect is highly detrimental. A method to compensate for the effect on the Doppler measurements without changing the receiver architecture is presented. Results with real static data and simulated low-Earth orbit data show that applying the compensation algorithm yields errors similar to those with a near-perfect oscillator. Copyright © 2015 Institute of Navigation.