Inversion of reflectance of ground object in urban areas based on SPOT-5 Dimap and dark-object

With the improved spatial resolution, SPOT-5 data has been an important tool for surveying and mapping application, land cover/land use in urban areas as soon as they was launched. In this paper, one SPOT-5 data in Shanghai urban areas was taken as an example, a fast atmospheric correction model based on SPOT-5 Dimap metadata and dark-object subtraction would be presented. At first, the paper gave a detailed introduction to metadata, tell how to process the data, and prepared for image rectification with Dimap. Secondly, the top of atmosphere reflectance (rho_TOA) was calculated, and all of the required parameters can be retrieved from the Dimap metadata. Third, the post atmospheric correction reflectance (rhoPAC) was calculated. The approach was based on the traditional dark-object subtraction (DOS) technique, according to the reasonable analyzes on dark-object and associated with the atmospheric radioactive transfer models. In order to evaluate and validate the correction results, we used NDVI to analysis the original images (before atmospheric correction) and after atmospheric correction of images. As a result, it shows that the reflectance of ground object by the method in the paper can eliminate the atmospheric scatter influence effectively and the edges of the surface objects are distinct and easy to identify. Therefore, based on this fast atmospheric correction algorithm in this study, we can retrieve the reflectance of ground object from the imagery itself for all the required parameters can be derived from the information contained in the imagery metadata.