Troposphere Refraction Correction Above A Non-uniform Underlaying Surface

The research on astronomical refraction and error correction of radar wave has long been undertaken in China and abroad. Recent years, more and more outcomes have been achieved due to the upgrades of electronic measurement hardware and the optimization of data processing methods. With the reduction of error probability of external measurement equipment, the error caused by astronomical refraction thus becomes one of the key factors that affect the precision of radar measurement system. Therefore, to strengthen the research on the refractive error correction of radar wave and so as to design an efficient correction system is of great significance to improving the precision of radar measurement and promoting the modernization of national defense, industry and agriculture.The thesis starts with a theoretical analysis of radar wave refraction effect, its impact on the measurement parameter of radar, and of the models of astronomical refraction rate correction. Upon comparison of several commonly-used methods for astronomical refraction correction, the author adopts the piecewise model of ground-based parameter prediction which hypothesizes the atmosphere is homogenous and delaminates linearly each section to improve the correction of refraction error.As for the area where atmospheric underlying surface is non-uniform, that is, where the atmosphere is inhomogeneous, considering that the refraction error is more evident in the lower atmosphere than in the upper one, a mixed sectional model is designed to further reduce the error probability. According to the model, the troposphere is divided into upper and lower layers. The spatial structure of lower layers is investigated by field method. Refraction error correction is actualized by the method of radial normal equation referring to refractive index profile of atmosphere. To correct the refraction error in upper atmosphere and neglect its heterogeneity, the above-mentioned ground-based parameter prediction method is followed.By comparing the corrected results obtained by the above-mentioned methods with those obtained by ray tracing method and troposphere microwave radiometer method under two climate conditions of two seasons in the same mountainous area, the author concludes that the proposed methods for refraction error correction is quite feasible in given areas and conditions for the correction of refractive distance and elevation angle.At the end of the thesis, the application condition and relative merits of the methods are given and the outlook for the atmospheric refraction error correction above a non-uniform underlaying surface is presented.