Session B6: Emerging PNT Consumer Applications

On the Evaluation of Multipath Suppression Using a Choke Ring Platform for Smartphone Multi-GNSS RTK Positioning
Phyo C Thu, Robert Odolinski, Yong Chien Zheng, National School of Surveying, University of Otago; Baocheng Zhang, State Key Laboratory of Precision Geodesy, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences; International Science and Technology Cooperative Offshore Center for Geodesy Frontier Technology; Li-Ta Hsu, Department of Aeronautical and Aviation Engineering, The Hong Kong Polytechnic University
Location: Prince David Room
Date/Time: Thursday, Apr. 16, 1:05 p.m.

The recent availability of raw Global Navigation Satellite System (GNSS) measurements on Android smartphones has accelerated research into low-cost real-time kinematic (RTK) positioning with mass-market devices. A key limitation is the embedded smartphone antenna, which is highly sensitive to multipath. This often leads to degraded carrier-to-noise density ratios (C/N0), reduced carrier-phase availability, and unreliable ambiguity resolution, particularly in signal-obstructed conditions. This study investigates whether a geodetic choke-ring, used as a passive platform without any electrical antenna connection, can improve the smartphone RTK positioning performance when using internal smartphone antennas. Experiments were performed using two Google Pixel 5 smartphones in a short-baseline phone-to-phone configuration in two environments: a low-multipath site and a medium-multipath site. For each environment, data were collected with and without the choke-ring platform. A u-blox ZED-F9P receiver with a patch antenna was included as a benchmark solution. All datasets were processed using instantaneous single-frequency (L1) RTK with double-differenced observations and an elevation-dependent stochastic model. Results show that the choke-ring platform increases mean C/N0 and improves carrier-phase tracking, with the most noticeable gains at moderate to high elevation angles. These improvements translate into substantially higher single-epoch ambiguity resolution success rates. In the low-multipath environment, the empirical integer least-squares success rate increased from 92.5% to 99.7% when using the choke-ring platform. In the medium-multipath environment, the success rate increased from 44.9% to 93.1%, while the average number of tracked satellites changed only marginally. Overall, the findings indicate that a passive choke-ring platform can provide a practical approach to improving smartphone RTK performance while using internal antennas, particularly under moderate multipath conditions.