Precise GNSS Positioning Using Smart Devices

Abstract

The recent access to GNSS (Global Navigation Satellite System) phase observations on smart devices, enabled by Google through its Android operating system, opens the possibility to apply precise positioning techniques using off-the-shelf, mass-market devices. The target of this work is to evaluate whether this is feasible, and which positioning accuracy can be achieved by relative positioning of the smart device with respect to a base station. Positioning of a Google/HTC Nexus 9 tablet was performed by means of batch least-squares adjustment of L1 phase double-differenced observations, using the open source goGPS software, over baselines ranging from approximately 10 m to 8 km, with respect to both physical (geodetic or low-cost) and virtual base stations. The same positioning procedure was applied also to a co-located u-blox low-cost receiver, to compare the performance between the receiver and antenna embedded in the Nexus 9 and a standard low-cost single-frequency receiver with external patch antenna. The results demonstrate that with a smart device providing raw GNSS phase observations, like the Nexus 9, it is possible to reach decimeter-level accuracy through rapid-static surveys, without phase ambiguity resolution. It is expected that sub-centimeter accuracy could be achieved, as demonstrated for the u-blox case, if integer phase ambiguities were correctly resolved.

The problem of GNSS positioning with measurements recorded using Android mobile devices

“…The release of GNSS measurements makes it possible to use proprietary calculation algorithms adapted to the limitations of the equipment and to field conditions of positioning. It also provides an opportunity to analyse the acquired GNSS observations outside the recording device, using external software [1], [2].…”

A Controlled-Environment Quality Assessment of Android GNSS Raw Measurements

“…Among these implementations, for instance, Doppler filtering and augmentation were investigated in Reference [4] to reach submeter accuracy. By exploiting carrier-phase observations on the enabled models, it is also possible to smooth code-based pseudorange measurements and reach decimeter-level accuracy without phase-ambiguity resolution, as successfully proposed in Reference [5]. The recent push to achieve precise positioning from Android smartphones thanks to the availability of their raw measurements has also been boosted by the release of a white paper from the European GNSS Agency (GSA) [6].…”

Nadir-Dependent GNSS Code Biases and Their Effect on 2D and 3D Ionosphere Modeling

“…These varying biases of the code observables are also referred to as group delay variations (GDV).Previous studies by Wanninger and Beer [11] and Wanninger, Sumaya, and Beer [12] have shown that nadir-dependent GDV affect precise point positioning (PPP) based on the single frequency ionosphere-free combination, wide-lane ambiguity fixing based on the Hatch-Melbourne-Wübbena linear combination [13][14][15], as well as TEC estimation of the ionosphere. The latter is an important characteristic of the ionosphere and is necessary in some single frequency precise positioning applications, for instance, precise positioning with mobile devices, which has gained significant attention in recent years [16][17][18][19][20][21][22][23][24][25][26][27]. For the verification and further understanding of these effects, the independent evaluation of previously used methods is therefore important.In this study, we investigated how nadir-dependent GDV affect ionosphere modeling by analyzing the model residuals that they give rise to.…”