Assessment of GNSS Zenith Total Delay Estimation Using Smart Devices

Global Navigation Satellite System (GNSS) have been routinely used in the last decades to estimate water vapor content in the lower part of the atmosphere. Water vapor measurements have been successfully integrated in Numerical Weather Prediction (NWP) models, showing a positive impact on the forecast of rain events. Since few years, it is possible to obtain raw measurements from the GNSS receivers embedded in smart device such as smartphones and tablets. Due to the ubiquity of such devices, retrieving information about the troposphere from them would be of great interest. In fact, this would widen the possibility to monitor the water vapor field at high resolution. This contribution evaluates the quality of the Zenith Total Delay ( ZTD) derived from a Nexus 9 tablet and a Xiaomi MI8 smartphone for a long static session. Such quantity can be linked to the water vapor content of the atmosphere using local meteorological data. The results are evaluated against a geodetic grade dual-frequency receiver showing a bias of around 3 mm with a standard deviation of 5 mm.