Development and Evaluation of Single-Frequency High-Precision PPP-RTK for Low-Cost GNSS Receiver

Hong-Woo Seok, Kutubuddin Ansari*

The rise of mobility, such as Urban Air Mobility (UAM) and autonomous driving, as well as robotics technology in the agricultural industries, has created a demand for high-precision GNSS positioning. In these cases, error correction using Observation Space Representation (OSR) or State Space Representation (SSR) is essential for high-precision navigation. The OSR correction provides the summation of errors through observations, high bandwidth is required, and is vulnerable to latency. Primarily, this approach is used for Real-Time Kinematic (RTK) positioning. The single-RTK has a constraint in baseline because of spatial decorrelation, but the Network-RTK has the drawback of necessitating two-way communication. These limitations can be solved by using SSR correction, which is less sensitive to latency and needs just one-way communication. As low bandwidth is required, it is also optimized for multiple user services and provides correction for each error source, rather than their summation. Additionally, the possibility of high-precision navigation with a single-frequency becomes possible with the increment of satellite constellations. In the current study, a suitable single -frequency PPP-RTK algorithm for low-cost receivers was developed using Geo++ GNSMART-based SSRG offered by National Geographic Information Institute (NGII). The SSRG is provided by dividing the error sources into satellite orbit, satellite clock, satellite signal bias, and gridded tropospheric and ionospheric delay. A navigation filter for a low-cost receiver was designed and implemented, along with an appropriate correct method for each error source. The performance of the proposed algorithm was evaluated through experimentation in Sejong-si, divided into static and dynamic environments. As a result of the experiment, the positioning accuracy was shown at cm-level stably, confirming the availability of low-cost GNSS receivers and smartphones.

Keywords: SSR, PPP-RTK, multi-constellation, low-cost receiver