Hi All, We recently purchased some IKONOS data for our study area. We got the geo-ortho kit with RPC's 15CE 90 (11bit) Having orthorectified the imagery using a 15m DEM I am now attempting to atmospherically correct the data using FLAASH. Following the ortho I converted the 11bit data to at aperture-radiance using the calibration coefficients supplied by space imaging http://www.geoeye.com/pro.../ikonos/spectral.htm According to the spaceimaging website the data are then in microwatts/cm2/steridian (suitable for FLAASH). I then commence with the atmos correction filling all the appropriate values in FLAASH (no pan so have set index to first band to'1'). The algorithm runs and the output data are loaded. Visually the corrected data seems correct however, when I look at a spectral profile all of the visible channels are negative with only the nir returning positive pixel values!! Can anyone suggest where I am going wrong or point out an incorrect assumption I am using ENVI 4.3 on a windows XP machine. Many thanks in advance for your help and input, Wesley Roberts