Abstract
The use of GPS positioning and navigation capabilities in mobile phones is present in our daily lives for more than a decade, but never with the centimeter level of precision that can actually be reached with several of the most recent smartphones. The introduction of the new GNSS systems (Global Navigation Satellite Systems), the European system Galileo, is opening new horizons in a wide range of areas that rely on precise georeferencing, namely the mass market smartphones apps. The constant growth of this market has brought new devices with innovative capabilities in hardware and software. The introduction of the Android 7 by Google, allowing access to the GNSS raw code and phase measurements, and the arrival of the new chip from Broadcom BCM47755 providing dual frequency in some smartphones came to revolutionize the positioning performance of these devices as never seen before. The Xiaomi Mi8 was the first smartphone to combine those features, and it is the device used in this work. It is well known that it is possible to obtain centimeter accuracy with this kind of device in relative static positioning mode with distances to a reference station up to a few tens of kilometers, which we also confirm in this paper. However, the main purpose of this work is to show that we can also get good positioning accuracy using long baselines. We used the ability of the Xiaomi Mi8 to get dual frequency code and phase raw measurements from the Galileo and GPS systems, to do relative static positioning in post-processing mode using wide baselines, of more than 100 km, to perform precise surveys. The results obtained were quite interesting with RMSE below 30 cm, showing that this type of smartphone can be easily used as a low-cost device, for georeferencing and mapping applications. This can be quite useful in remote areas where the CORS networks are not dense or even not available.
Highlights
The use of Global Navigation Satellite Systems (GNSS) is nowadays an indispensable tool in areas such as terrestrial, maritime, or aerial transportation, agriculture and forestry, fisheries, financial services, emergency, leisure and recreational activities, mobile services, location, cartography, and many other in which the use of georeferenced information allows for efficiency gains
Three scenarios contributed to this evolution: the first was the introduction of the Android 7.0 Nougat, by the Google company in May 2016 [2], in the smartphones which allow access to the raw code and phase GNSS measurements; the second was the availability of Galileo signals in the smartphones, allowing access to the capabilities of this system characterized by the advanced atomic clocks, the new techniques of signal modulation as the AltBOC, the higher resistance to spoofing and jamming interferences; the third was the introduction, in May 2018, of the Broadcom BCM47755 chip with dual frequency L1/L5 [3]
Errors are less than 25 cm in most cases for the long baselines, 277 km (CASC) and 645 km (CEUT), and as expected, the best results were obtained with the shorter baselines, with the GAIA (0.2 km) station showing results better than 15 cm
Summary
The use of Global Navigation Satellite Systems (GNSS) is nowadays an indispensable tool in areas such as terrestrial, maritime, or aerial transportation, agriculture and forestry, fisheries, financial services, emergency, leisure and recreational activities, mobile services, location, cartography, and many other in which the use of georeferenced information allows for efficiency gains. Providing Positioning, Navigation, and Timing (PNT) services, GNSS systems have been asserting themselves as enhancers of a wide range of applications with an impact on people’s quality of life. These capabilities in mobile phones have evolved in a way that they allow today’s precisions in positioning never achieved in this market segment and, until recently, only achieved using the expensive and high performance GNSS geodetic receivers. This possibility can be explored in some areas as a lower-cost alternative to the expensive professional GNSS geodetic equipment. Three scenarios contributed to this evolution: the first was the introduction of the Android 7.0 Nougat, by the Google company in May 2016 [2], in the smartphones which allow access to the raw code and phase GNSS measurements; the second was the availability of Galileo signals in the smartphones, allowing access to the capabilities of this system characterized by the advanced atomic clocks, the new techniques of signal modulation as the AltBOC, the higher resistance to spoofing and jamming interferences; the third was the introduction, in May 2018, of the Broadcom BCM47755 chip with dual frequency L1/L5 [3]
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