An Assessment of Low-cost Single-frequency RTK Receivers for Ionosphere-weighted Baselines with L1 GPS, B1 BDS, E1 Galileo and L1 QZSS Observations
Robert Odolinski, National School of Surveying, University of Otago, New Zealand; Peter J. G. Teunissen, GNSS Research Centre, Curtin University of Technology, Australia and Delft University of Technology, The Netherlands
The emerging GNSSs make single-frequency (SF) RTK positioning possible. In this contribution we will look at three different types of low-cost (few hundred USDs) RTK receivers that can track L1 GPS, B1 BDS, E1 Galileo and L1 QZSS, or any combinations thereof. These SF RTK receivers can potentially give competitive ambiguity resolution and positioning performance to that of more expensive (thousands USDs) dual-frequency (DF) GPS receivers. This is however only true if all the systems tracked are combined. We will first focus on formulating a realistic stochastic model through least-squares variance component estimation (LS-VCE), which will assure that our receivers at hand can achieve the best possible ambiguity resolution and RTK positioning performance. The low-cost SF RTK receivers/antennas will then be assessed against DF GPS receivers and survey-grade antennas for a location in Dunedin, New Zealand and Perth, Australia. We will analyze data with ionospheric disturbances at low, medium and high levels, thereby making use of the ionosphere-weighted model. It will be demonstrated that when the presence of the residual ionospheric delays increases instantaneous RTK positioning is not possible for any of the analyzed receivers, and a multi-epoch model is necessary to use. We will finally show that the low-cost SF RTK performance can then still remain competitive to that of the more expensive DF GPS receivers, with a better performance in Perth owing to the better visibility of the regional BDS and QZSS satellites.