Android positioning: from stand-alone to cooperative approaches

The request for continuous and accurate localization in most diverse environments is growing: a possible solution is the use of location information retrieved by smartphones. For Android devices, Global Navigation Satellite System-based positioning is one of the main localization source, but in some environments GNSS signals can be blocked or affected by multipath. In these circumstances, the navigation solution may experience severe degradation. The presence of multiple outliers and their exclusion can cause a significant reduction of the satellite geometry. A possible solution is the identification of blunders and the replacement of such measurements with observables provided by a nearby device. The merging of measurements from different devices is an open challenge that is addressed in this work. This paper analyzes three smartphone GNSS-based cooperative positioning approaches: Direct Measurement Sharing, where the aiding device provides its raw observations to the aided smartphone; Augmented Measurement Sharing, where clock parameters and their accuracy are shared along with the raw observables; Corrected Measurement Sharing CMS, where corrected observables are adopted. Specifically, measurements of the aiding device are at first corrected for the clock bias. The methods have been validated using static and kinematic real data: tests were performed using devices from three manufacturers with different versions of the Operating System (OS). From the tests, the effectiveness of the proposed methods is demonstrated and the benefits of the combined solutions with respect to the single device solutions are shown.