A simple atmospheric correction for HRSC-AX high resolution image data - examples and conclusions from HRSC flight campaigns

Abstract

The HRSC-A (High Resolution Camera - Airborne) systems are multiple line "pushbroom§ instruments developed by the German Aerospace Center (DLR). In the image data of the blue and green band the effects of atmospheric scattering are most prominent. The correction of atmospheric absorption is not addressed here. When strong atmospheric effects are observed, a simple atmospheric correction can be applied. This is done for each individual flightline and each channel seperately, based on view-angle dependet histrogram statistics. For the correction it is assumed that due to the small pixel size and the large area a significant number of pure shade pixels with a theoretical signal of 0 DN are covered across the whole swath. An across-track Dark-Pixel-Profile (DPP) is used to determine the vielw angle dependent correction offset. The shape of these profiles varies with the phase angle. This simple atmospheric correction has successfully been tested in several projects, clearly increasing the image homogeneity of the individual flightlines and als improving the quality of the resulting image mosaics. Local atmospheric effects within the flightlines (e.g. due to topography, adjacency effects) are not corrected.