Design and implementation of single frequency RTK positioning framework

Single-frequency GNSS receivers are widely available and cost effective. The widespread availability paired with the demand of higher positioning accuracy for commercial users has motivated application developers to use single-frequency carrier-phase based differential positioning solutions for mass market. Single-frequency differential positioning is expected to be the leading technology for a wide range of commercial applications ranging from wearables, tracking devices, mHealth to internet of things. This paper presents the design and implementation of a RTK positioning framework, using single frequency code and carrier-phase measurements. The system can be divided in three blocks with each block implementing least squares estimation to obtain an ambiguity resolved rover receiver's position per epoch. The implementation is tested for both static and kinematic data and positioning results are validated against those obtained from RTKLIB and CSRS-PPP. It is seen that the results tally within centimetre level. However, the positioning accuracy deteriorates once carrier-phase cycle slips occur. This is catered for by using a Hatch Filter based cycle slip detection algorithm which ensures that CS corrupted measurements are eliminated thus maintaining position accuracy. The framework can also serve as a test bench to design and test algorithms targeted towards single frequency RTK positioning.