332 / 2023-10-15 23:44:32

A GNSS-RTK terminal integrity monitoring algorithm considering the error characteristics of different environments

GNSS landslide monitoring; Integrity; Fault detection; Protection level; Reliability

The deformation of mines is closely related to the safety of people’s lives and property. As a commonly used technical means of deformation monitoring, the reliability and accuracy of GNSS real-time kinematic (RTK) positioning are equally important, which will directly affect the exactitude of monitoring, prediction and early warning. GNSS integrity monitoring (IM) is a vital research domain for assessing the reliability of positioning , and its aviation integrity field is the most mature. Aviation integrity monitoring calculates the protection level (PL) based on observation information, integrity support information (ISM) and predefined probability of hazardous misleading information (PHMI), and improves positioning reliability by ensuring that the positioning error (PE) is within the PL. However, the factors that need to be considered in the case of short baseline RTK monitoring are different from aviation and are mainly concentrated in the following three points. First, the observation environment is more complex, resulting in multi-paths that cannot be accurately eliminated by differencing and do not conform to Gaussian characteristics. Second, the cost of monitoring terminals is lower results in worse quality of observation data. Third, the GNSS-RTK positioning solution is centered on the carrier phase observations, so the correctness of the fixed ambiguity is crucial. Based on this, this paper proposes a GNSS-RTK terminal integrity monitoring algorithm that takes into account the error characteristics of different environments. This method obtains the upper bound mean and standard deviation of different landslide environments through the double upper bound cumulative density function to solve the horizontal protection level (HPL) and vertical protection level (VPL),and validates the effectiveness of the integrity monitoring algorithm by evaluating the probability of protection level being upper bounds for positioning error (PE). Experimental analysis shows that, the envelope rate (PE<PL) in different environments is 100%, which meets the integrity risk requirements of this paper. When the alert limit (AL) is set to 0.1m, in open environments ,the availability rate of horizontal and vertical positioning results (PE<PL<AL) both reach 100%, in complex environments ,the availability rate of horizontal positioning results reaches 99.981%, and the availability rate of vertical positioning results reaches 99.949%. At the same time, the data used in the open environment and complex environment also represent the data of the slope sliding stage and the stable stage respectively, which can show that the integrity algorithm in this paper also meets the requirements of integrity risk in different deformation stages, and the availability of positioning results reaches more than 99.9%.