Testing of an Ultra-tightly coupled GPS/INS under Strong Ionospheric Scintillation

Abstract

Ionospheric anomalies are major error sources that affect the performance of the GPS (Global Positioning System). In particular, ionospheric scintillation may cause GPS satellite signal loss, and multiple losses can degrade the availability of positioning/navigation services such as GBAS (GroundBased Augmentation Systems). In order to improve the tracking performance of GPS receivers under scintillation conditions, an ultra-tightly coupled GPS/INS (Inertial Navigation System) integrated system has been developed and flight tests to evaluate it were conducted around the island of Ishigaki where ionosphere scintillation frequently occurs. Evaluation of phase tracking performance was carried out off-line using a software-defined GPS receiver which processes stored IF (Intermediate Frequency) data. The use of INS enabled a longer integration time of GPS signals, which increased the signal-to-noise ratio (SNR). As a result, the tracking loop of GPS/INS achieved continuous phase tracking even under strong scintillation conditions.