| Interferometric calibration technology is an important way to improve the accuracy of In SAR DEM products.However,the traditional least square estimation method uses multi-parameter modeling for interferometric calibration,the parameter coupling phenomena is serious,and the robustness of error estimation cannot be guaranteed.Based on this,this paper deeply studies the influence of the spatial distribution characteristics of the interference parameter error,analyzes the direct and indirect influence of the elevation error on the baseline parameters and the interference phase,and proposes an improved spaceborne SAR interferometry calibration method,which effectively solves the problem of parameter error coupling.At the same time,this paper will provide a technical reference for my country’s L-band differential interferometric SAR(Lutan-1,LT-1)satellite for the 1:50,000-scale topographic map data collection task of the global cloudy and rainy area.The main research results are as follows:(1)The engineering method of In SAR terrain mapping is studied.The engineering method of In SAR terrain mapping proposed in this paper consists of nine steps,which are: registration,calculation of interference fringe pattern and coherence coefficient map,removal of flat ground phase,interferogram filtering,phase unwrapping,recovery of absolute phase,phase height transformation,geography Coding,accuracy evaluation.This method will be w IDely applicable to the In SAR process of LT-1 to produce DEM.(2)A spaceborne SAR interferometric calibration method based on the spatial distribution of elevation errors is studied.In this paper,considering the difference in the distribution characteristics of the elevation errors caused by the spaceborne SAR interference parameters,the spaceborne SAR interference parameter errors are divided into two independent errors,the absolute phase error and the baseline error,which are calibrated separately to avoid the error coupling problem of the interference parameters.Among them,the In SAR absolute phase error estimation method uses a large amount of high-precision ICESat laser altimetry data to solve the absolute phase at the target point,and estimates the whole cycle unknown of the absolute phase by unwrapping the phase and the ground phase,so as to achieve the purpose of compensating the interference phase error.The In SAR baseline error calibration method decomposes the baseline error into parallel baseline error and perpendicular baseline error.First,the slope error term is used to solve the parallel baseline error,and then the perpendicular baseline error is solved according to the geometric relationship of interference.The correction of the original baseline also avoids the error coupling problem of the two baseline components.(3)The accuracy verification method of interferometric calibration model is studied.Experiment 1 proposes a method to verify the correction accuracy of the baseline calibration model by adding different errors to the simulated SLC data.The results show that this method can correct 96.86% of the parallel baseline error and 83.8% of the perpendicular baseline error on average.Experiment 2 used the Terra SAR-X/Tan DEM-X interferometric data in Datong City to verify the feasibility.The results showed that the error in the elevation was reduced by at least31% after calibration,and the worst accuracy reached 3.5 m.In the third experiment,the universality verification was carried out with the far and near wave position interference data of the XX satellite in Xinjiang.The results show that the error in elevation is reduced by at least7.89 m after calibration,about 72.12%.To sum up,the spaceborne SAR interferometric calibration method based on the spatial distribution characteristics of the elevation error proposed in this paper is effective and feasible,and will prov IDe technical reference for the topographic mapping task of LT-1.The paper has 50 figures,17 tables,and 85 references. |
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