Currently, TIR data from Landsat 5-TM, Landsat 7-ETM+ and Landsat 8-TIRS can be atmospherically corrected using the on-line Atmospheric Correction Parameter Calculator (ACPC, http://atmcorr.gsfc.nasa.gov). For specific geographical coordinates and observation time, the ACPC provides the atmospheric transmittance, and both upwelling and downwelling radiances, which are calculated from MODTRAN4 radiative transfer simulations with NCEP atmospheric profiles as inputs. Since the ACPC provides the atmospheric parameters for a single location, it does not account for their eventual variability within the full Landsat scene.
The new Single Band Atmospheric Correction (SBAC) tool provides the geolocated atmospheric parameters for every pixel taking into account their altitude. SBAC defines a three-dimensional grid with 1°×1° latitude/longitude spatial resolution, corresponding to the location of NCEP profiles, and 13 altitudes from sea level to 5000 meters. These profiles are entered in MODTRAN5 to calculate the atmospheric parameters corresponding to a given pixel are obtained by weighted spatial interpolation in the horizontal dimensions and linear interpolation in the vertical dimension.
In order to compare both SBAC and ACPC tools, we have compared with ground measurements the Landsat-7/ETM+ LST obtained using both tools over the Valencia ground validation site.