Happy New Year! I have tried to co-registered the images, however, the "map info" of those co-registered images were gone after I re-opened them again in the "avaliable band list" Therefore, I have to do all the analysis at once before I shut the software. However, even I coregistered the images, I cannot link them together. I am 100% sure that both images cover the same area and with same coordiante system. However, the system pops up an error " There is no common data with which to link these displays. No link established" Furthermore, when I try to perform NDVI of co-registered image (A) - NDVI of co-registered image (B), after i chose NDVI from image (A), the NDVI from image (B) disappeared in the list. I really do not know what to do, I am thinking the problem might be due to the map projection. However, I do not know how I can edit the map projection in hdr.file. Could anyone please help me? Thank you very much .