Objectives Using global navigation satellite system reflectometry (GNSS-R) method to monitor road slope deformation has the advantages of large area and high efficiency. At present, there are three problems to be solved in the research based on this method. First, the errors caused by satellite motion need to be corrected. Second, it is necessary to evaluate the influence of antenna position of reflection signal on the accuracy of deformation inversion. Third, it is necessary to carry out experiments on actual road slopes.
Methods By analyzing the phase difference between reflected GNSS signal and direct GNSS signal from road slope, deformation inversion of real slope is carried out. The effects of GNSS satellite movement and the position migration of the reflected signal receiving antenna on the accuracy of deformation inversion are analyzed. A correction method is proposed which can be applied to both medium earth orbit (MEO) and inclined geosynchronous orbit (IGSO) satellite motion and geostationary orbit satellite micro-position deviation. A method to calculate the maximum acceptable antenna position offset based on the reflecting surface area is presented.
Results The results show that the inversion errors of MEO satellite for 28.0 cm and 11.7 cm position offsets are 1.97 cm and 0.56 cm respectively, which are reduced by 3.03 cm and 2.70 cm compared to before correction. Through the experiment of receiving antenna position offset, it is concluded that the deformation estimation and inversion results will not be affected when the antenna position is within about ±6° and ±5° in the center direction of the main lobe migration in the long side and the short side directions of a rectangular reflector respectively.
Conclusions The accuracy of deformation inversion will not be affected when the position deviation of the reflector antenna is within the acceptable range that can be calculated. All these will provide reference for the future application of GNSS-R deformation monitoring technology.
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