[QUOTE]yyihdegowoldeyohanne@students.la wrote I have got a new project that  aims to identify the springs discharging to sea along the coastal area, Western Victoria, Australia. which image is suitable to identify the springs beneath the surface along the coastal inle?  Landsat (thermal band) or ASTER image?  Could there be a possibilty to identify the springs without converting the DN to radiance and again to temprature, just by merely stretching the DN using the thermal band of landsat? I would appareciate if you assist me on how to proceed with the details of the procedure in both Landsat and ASTER images since I havenot done like this before. Also, does ASTER image has a night time record? I guess Landsat has only day time scenes. I think the night time scene would helpful to get  better temprature contrast between the springs and sea water.Which ASTER image do I need to order ? Thanks Yohannes   [/QUOTE]