An ionosphere-weighted calibration method with multi-station network corrections

Abstract

Ionospheric delay is one of the most dominant error sources in GNSS fast relative positioning, especially for RTK positioning of medium and long baselines, which directly affects the ambiguity fixing successful rate and positioning accuracy. The strategy of combining ionospheric correction based on multi-reference station network with ionospheric weighted model is still one of the most effective methods for precise relative positioning. In this paper, a method of ionospheric weighted calibration model is presented. By using a large-scale reference station network at a certain period of time with ionospheric disturbance to obtain the prior ionospheric information required by the user, the GNSS precision relative positioning performance of the ionosphere-weighted calibration model in complex scenarios (the accuracy of prior ionospheric information will be reduced due to large-scale reference station network and ionospheric active scene) was systematically evaluated. The experimental results show that the ionosphere-weighted calibration (IWC) method can effectively reduce the influence of excessive ionospheric modeling residual on the positioning results, and significantly improve the fixed rate and positioning accuracy of RTK. Compared with the traditional ionosphere-fixed model based on virtual reference station (VRS) technology, the three-dimensional accuracy and fixed rate of the six rover stations are improved by 56% and 33.5% on average. Secondly, the prior ionospheric constraint intensity in IWC mode is controllable, which can effectively balance the relationship between initialization speed and positioning accuracy. On average, 94.3% of the time period of the six rover stations can complete the initialization and fixing within 10 epochs, which can basically meet the requirements of fast positioning. In addition, IWC model can ensure higher accuracy and better maintain fixed solution state after the ionospheric parameter convergence is completed. In the ionospheric disturbance stage, after a period of parameter convergence, high fixed rate and positioning accuracy can still be guaranteed.