Evaluating the quality of gnss observables and the positional accuracy of the data collected by xioami mi 8 smartphone’s gnss chipset / Avaliando a qualidade dos observáveis gnss e a precisão posicional dos dados coletados pelo chipset gnss do smartphone xioami mi 8

In May 2016, Google LCC announced that GNSS raw data would be available to Android 07 users, thus allowing them to access GNSS observables data, both from carrier cycle count (phase) and pseudo distance measurements. Since then, several studies have tried to analyze the sources of positioning errors obtained with single and dual frequency GNSS chipsets inserted in different smartphone models. In this sense, the main goal of this study is to analyze the quality of GNSS observables and the positional accuracy of the final coordinates, obtained by processing GNSS raw data collected by the Xiaomi Mi 8 and to compare them to those obtained through conventional dual frequency GNSS receivers. Two processing strategies will be used for both datasets, namely: static relative positioning and IBGE Precise Point Positioning. The GNSS data, obtained by both the Xiaomi Mi 8 and the GRS-1 Receiver, manufactured by Topcon, was collected simultaneously, with a tracking time of 3 hours. The raw data was post-processed in RTKlib software in relative mode and in the IBGE PPP online platform. We realized that the signal quality, indicated by the carrier power-to-noise ratio and the carrier wave phase residuals were on average 10 db-Hz lower and 10 times higher for the satellites detected by the Xiaomi Mi 8 compared to the GRS-1 receiver, respectively. While the coordinate accuracy of the Topcon receiver ranged from 1 mm to 6 mm, those of the Xiaomi Mi 8 ranged from 17 cm to 53 cm.