Comparison test and research progress of topographic correction on remotely sensed data
遥感影像地形校正研究进展及其比较实验

In remotely sensed image from rugged terrain the sunny surface shows more radiance than the expected and on the shady surface the effect is the opposite.That is to say,a high variation in the reflectance response for the same land use/land cover types is caused by the irregular shape of the terrain.Therefore,the removal of the topographic effect named topographic correction may be critical in areas of rugged terrain,as a preliminary step to the estimation of land surface parameters for Landsat ETM image.And then the concept and goal of topographic correction was briefly introduced and then various algorithms for topographic correction developed internationally were reviewed and summarized.Many researches have been carried out on topographic correction and many topographic correction algorithms have been put forward such as cosine correction,C correction,SCS correction,SCS C correction,Minnaert correction etc.However,there is no clear consensus on methods that may be universally applicable.The main difficulty in applying topographic corrections is related to the lack of standard and generally accepted models.So a correction test was carried out in this study to compare 11 existing popular methods of topographic correction,including a new one named VECA developed by ourselves,and see how successfully they can be applied to Landsat-7 ETM image.The test site was selected on the relatively rugged terrain located on the southern piedmont of the Qinling Mountains.And then visual comparison and statistical analysis were adopted for feasible evaluation of the 11 topographic correction methods,and the results suggested that VECA correction,b correction,C correction,Teillet-regression correction,SCS C correction Minnaert correction and Minnaert-SCS correction have good correction performance,however,the Cosine-T correction,Cosine-C correction,SCS correction and Cosine-b correction would overcorrect the shaded areas in image;and the VECA and b correction are the most capable ones for removing the topographic effects contained in ETM image among the 11 methods,compared with b correction,VECA was not only better in performance on topographic effects removal but also simple in theory and easy for operation.In the last section of this paper,the problems and difficulties existing in topographic correction were discussed,and the future hot points and research focuses were discussed.