Benefits of receiver clock modeling in code-based GNSS navigation

Abstract

Due to the limited frequency stability and poor accuracy of typical quartz oscillators built-in GNSS receivers, an additional receiver clock error has to be estimated in addition to the coordinates. This leads to several drawbacks especially in kinematic applications: At least four satellites in view are needed for navigation, high correlations between the clock estimates and the up-coordinates. This situation can be improved distinctly when connecting atomic clocks to GNSS receivers and modeling their behavior in a physically meaningful way (receiver clock modeling). Recent developments in miniaturizing atomic clocks result in so-called chip-scale atomic clocks and open up the possibility of using stable atomic clocks in GNSS navigation. We present two different methods of receiver clock modeling, namely in an extended Kalman filter and a sequential least-squares adjustment for codebased GNSS navigation using three different miniaturized atomic clocks. Using the data of several kinematic test drives, the benefits of clock modeling for GPS navigation solutions are assessed: decrease in the noise of the upcoordinates by up to 69 % to 20 cm level, decrease in minimal detectable biases by 16 %, and elimination of spikes and subsequently decrease in large position errors (35 %). Hence, a more robust position is obtained. Additionally, artificial partial satellite outages are generated to demonstrate position solutions with only three satellites in view.

Chip-scale atomic devices

“…Similar results were presented in other work. 200 Precise timing at low power consumption is also of value for seismic measurements on the ocean floor related to earthquake detection, acoustic sensing, and oil exploration. Gardner et al 201 describe the deployment of 13 commercial chip-scale atomic clocks for 6 months in ocean-bottom seismographs for microearthquake monitoring, for which timing accuracies of $1 ms are required.…”

Precise time and frequency transfer combined BeiDou’s RDSS and RNSS signals

“…4 and 6, we can effectively reduce the observation noise of RNSS signals, thereby improving timing accuracy. According to the results of the relevant paper [15][16][17][18], the time synchronization accuracy can reach several ns level.…”

Low-Cost GNSS Software Receiver Performance Assessment

“…The PVT solution performance completely relies on clock measurements; indeed, space vehicles and receiver clocks must be as synchronized as possible with respect to the GPS time (GPST). GNSS satellites are equipped with very precise atomic clocks, while receivers, especially the low-cost ones, are often equipped with Temperature-Compensated Crystal Oscillator (TCXO) clocks that exhibit a noisy short-term stability and a poor long-term stability [1]. The satellites' clock offsets are corrected through parameters encapsulated in the navigation message broadcasted by the Ground Control Segment.…”