Abstract
The number of Android devices enabling access to raw GNSS (Global Navigation Satellite System) measurements is rapidly increasing, thanks to the dedicated Google APIs. In this study, the Xiaomi Mi8, the first GNSS dual-frequency smartphone embedded with the Broadcom BCM47755 GNSS chipset, was employed by leveraging the features of L5/E5a observations in addition to the traditional L1/E1 observations. The aim of this paper is to present two different smartphone applications in Geoscience, both based on the variometric approach and able to work in real time. In particular, tests using both VADASE (Variometric Approach for Displacement Analysis Stand-alone Engine) to retrieve the 3D velocity of a stand-alone receiver in real-time, and VARION (Variometric Approach for Real-Time Ionosphere Observations) algorithms, able to reconstruct real-time sTEC (slant total electron content) variations, were carried out. The results demonstrate the contribution that mass-market devices can offer to the geosciences. In detail, the noise level obtained with VADASE in a static scenario—few mm/s for the horizontal components and around 1 cm/s for the vertical component—underlines the possibility, confirmed from kinematic tests, of detecting fast movements such as periodic oscillations caused by earthquakes. VARION results indicate that the noise level can be brought back to that of geodetic receivers, making the Xiaomi Mi8 suitable for real-time ionosphere monitoring.
Highlights
The noise level obtained with VADASE in a static scenario—few mm/s for the horizontal components and around 1 cm/s for the vertical component—underlines the possibility, confirmed from kinematic tests, of detecting fast movements such as periodic oscillations caused by earthquakes
The technological innovations introduced by Google in smartphone and internet of things (IoT) devices during the past two years started a revolution within the mass-market GNSS world
RINEX files from a Xiaomi Mi 8 were obtained in this work using rinex ON [21], which is the only RINEX logger able to decode GNSS measurements and navigation messages (RINEX 3.03 format): the only two types of information required to perform analyses in real-time scenarios with VADASE and VARION
Summary
The technological innovations introduced by Google in smartphone and internet of things (IoT) devices during the past two years started a revolution within the mass-market GNSS world. The release of the Android Raw GNSS Measurements API (Figure 1), compatible with Android 7.0 or higher, allows app developers to access the internal position–velocity–time (PVT) solution, and the raw GNSS measurements. This enables the reconstruction of pseudorange, carrier-phase, Doppler, and signal-to-noise ratio (SNR) observables. The real turning point was the release of the Xiaomi Mi 8 in May 2018 This device is the first multi-GNSS dual-frequency (L1/E1 and L5/E5a) smartphone using the new Broadcom BCM47755 GNSS chipset. The release of Android 9, which allows the acquisition of carrier-phase measurements not affected by duty cycle—a battery-saving mode leading to continuous cycle slip in carrier-phase measurements—indicates the leading position that Android is assuming within the mass-market GNSS world
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