I am a master student and failed after several attempts that lasted for many weeks I decided to ask my question to you. My query is that I have a product from Modis 1B dealing in ENVI and I tried Method in a previous study to separate the surface from the atmosphere including clouds. I have read a lot and have received threshold methods but threshold measures vary depending on characteristics For example: CHr1 gt 0.2 and lt 0.35 when CHr1 is band4ref This method separates the surface from the ground Secondly CHbt 31 gt 270 . also if ( ch31K-ch20K) lt -26 HOW value come Negative number (( I want understand that, plz ))

anyway . Based on previous search elsewhere. And I have to find The method suitable for my method so I have to know the measurements of reflective and thermal bands Method of dealing with MODIS data .. I mean measuring BTT & REF to be able to know the surface of the Earth and the atmosphere .. If there is a reference to that .. thankful for your support ..

note "( for more clearly i attach the paper if any one want read it )