UniBwM researchers achieved unprecedented 1-2 cm (!) Accurate GNSS positioning with commercial smartphone

18 Oktober 2019

Authors: Himanshu Sharma, Mohamed Bochkati, Gerhard Kestel, Thomas Pany

With the introduction of Broadcom BCM47755 dual frequency chip in 2017 and the access of GNSS raw measurement to the user via Android API, the researcher have been working to analyze the quality of GNSS raw measurements from the dual frequency smartphone (Xiaomi MI8). Various new domain like LBS application development, implementation of OS-NMA message in smartphone and the new techniques to provide GNSS user with precise positioning, has emerged in last few years. Using the carrier phase measurements for the precise positioning has always been a great challenge for the mass market GNSS receiver manufactures due to the trade-off between cost and performance. The availability of carrier phase measurements in smartphone and need of market for cm level accuracy, has aspire the researcher to work more intensively towards precise positioning in Smartphone. Easier said than done, carrier phase measurements from smartphones brings an old age problem of cycle slips. In addition to this, power optimization features like duty cycling, which limits the GNSS chip from continuously tracking the satellites, does no good to the aim of achieving high accuracy.

We at the Universität der Bundeswehr, Neubiberg have been extensively working on performing RTK positioning with the Smartphone raw measurements. In order to compensate for the multipath effects from the ground reflection and destruct the reflected waves travelling parallel to the ground plane, which is somehow a major degradation factor in smartphone positioning, we performed an out of the box experiment by putting smartphone on the choke ring platform. The choke ring due to its multipath rejection capability, was assumed to be a critical factor in improving the quality of signal reception by rejecting dominant multipath.

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The choke ring platform with smartphone (Xiaomi Mi8) mounted on the top, was placed on the rotating platform. Trimble R10 as RTK base station was kept next to the setup. The data set was logged for around 50 minutes using Geo++ Logger and processed with high quality post processing tool.

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The positioning results were quite impressive showing 84 percent ambiguities fixed with cm level accuracy.

 

Rover of the observation (RINEX)

Reference of the observation (RINEX)

The Project work is funded by Federal Ministry for Economic Affairs and Energy and managed by German Aerospace Agency (DLR).