GNSS Fault Detection and Mitigation using Android IMU

Abstract

Applications of location information provided by Android devices have been expanding rapidly due its prevalence in the technology market. However, as the development focus of the Global Navigation Satellite Systems (GNSS) chipsets inside smartphones are not only accuracy, precision, and integrity, but also power consumption and size constraints, the Android GNSS hardware and software are more susceptible to signal attenuation and interference compared to high performance geodetic GNSS receivers. For example, the Android GNSS navigation engines are more vulnerable to the effects of signal multipath and experience more frequent carrier phase cycle slips in reduced GNSS signal quality environments such as urban canyons. Although standalone smartphone GNSS receivers have these limitations, some of the smartphones have access to additional sensors for accuracy and integrity support, such as accelerometers and gyroscopes. In this paper, the effectiveness of the accelerometers and gyroscopes inside Android devices, in supporting the standalone Android GNSS receivers will be investigated. The investigation will use the smartphone embedded sensors for device-independent performance that is not reliant on any other external sources of information. The additional sensors will be mixed with the GNSS measurements through a tightly-coupled extended Kalman filter, and potential faults will be flagged and mitigated using the innovation metrics. The GNSS measurements will be singled differenced to remove the effects of clock bias and drift on the filter. The orientation of the device will be determined using the accelerometer and gyroscope, and complemented using the GNSS measurements. Also, the thresholds for the innovation metrics will be computed using nominal open-sky data. The novelty of the paper will be looking at how the additional smartphone sensors can be used to improve the position solution from the smartphone, and also detect and mitigate potential faults in the GNSS measurements due to multipath or carrier phase cycle slips.