Do you mean like in a paragraph? I think books have been written on this subject. I know I have been working on an algorithm in IDL to remove clouds in LandSat images part-time for several months now. It doesn't really seem to be the kind of thing that can be done or explained easily. If it can, I would say that whatever method is being used isn't doing it correctly. :-)

Thanks Fanning, Would u be kind enough to provide names of such books?

I think rather than reading a book, I would urge you to do a Google search on "removing clouds from satellite images" and then just plow into the 3.2 million articles you find. Probably after reading a couple hundred thousand of them you will be enough of an expert to write your own book! :-) The point is, this is a hot topic, with a lot of smart people working and writing about it. If it could be explained in a paragraph, someone would have done it, and it would show up first in your Google search. The fact that it doesn't ought to tell you something.

Thanks once again i truly appreciate