5.3 Topographic Correction

In previous sections, we attempted to correct the atmospheric effects, i.e. convert image digital numbers DNs to image radiance Ls. After atmospheric correction, we expect to have the spectral reflectivity r.

Assume that atmospheric effects can be completely removed from the image, the spectral reflectivity obtained contains the real target reflectance r and the topographic modification during image acquisition, G.

= r ï G

The G contains information about the viewing and energy incidence geometric relationship.

Moon can be considered approximately as a surface that reflects equal amount of light in all directions.

5.3.1 The role of relief

5.3.2 Gradient Space