Optimal antenna topologies for spatial gradient detection in differential GNSS

Abstract

This paper describes new methods to determine optimal reference antenna topologies for detection of spatial gradients in differential Global Navigation Satellite Systems (GNSS). Such gradients can be caused by ionospheric fronts and orbit ephemeris faults, and if undetected, represent major threats to aircraft navigation integrity. Differential carrier phase measurements between ground antennas are highly sensitive to spatial gradients. Therefore, monitors using spatially separated ground antennas have recently attracted great interest. However, they cannot detect gradients of all sizes and directions due to the presence of integer ambiguities. These ambiguities cannot be resolved because the gradient magnitude is unknown a priori. Furthermore, the performance of such monitors is highly dependent on the spatial distribution of reference antennas. In this work, we introduce new methods to find optimized antenna topologies for spatial gradient detection.

Ground-Based Augmentation Systems Operation in Low Latitudes - Part 1: Challenges, Mitigations, and Future Prospects

“…Figure 9 shows an example of a rectangular box orientation of reference receiver antennas for a GAST-D facility with antenna separation distances identified as a and b (where a and b might be the same or different) (Reuter et al 2012). Several analyses of possible receiver orientations and separation distances have been conducted (e.g., see Jing et al 2015), mostly suggesting separations from 150 m to 1 km. On the airborne side, two additional monitors targeted at ionospheric threats are included when using GAST-D: the dualsolution ionospheric gradient monitoring architecture (DSIGMA) and an airborne CCD monitor similar to the one implemented on the ground (Pullen et al 2017).…”