Atmospheric / Topographic Correction for Satellite Imagery (ATCOR-2/3 User Guide, Version 8.2 BETA, February 2012) R. Richter1 and D. Schl¨apfer2 1 DLR - German Aerospace Center, D - 82234 Wessling, Germany 2ReSe Applications, Langeggweg 3, CH-9500 Wil SG, Switzerland DLR-IB 565-02/12 2 The cover image shows a true color subset of a Landsat-7 ETM+ scene with lake Constance at the Austrian-German-Swiss border (top left), acquired 2 June 2000. The top right image is the atmospherically corrected scene employing a haze removal over land and water. The haze removal over water is one of the new features of the 2011 release. The bottom part presents a zoomed view. The water mask is derived from the DEM file of this scene, because a unique water classification with exclusively spectral criteria is not possible in this scene. A correct water/land mask is critical for the quality of the separate haze removal algorithms over land and water. ATCOR-2/3 User Guide, Version 8.2.0, February 2012 Authors: R. Richter1 and D. Schl¨apfer2 1 DLR - German Aerospace Center, D - 82234 Wessling , Germany 2 ReSe Applications, Langeggweg 3, CH-9500 Wil SG, Switzerland c All rights are with the authors of this manual. Distribution: ReSe Applications Schl¨apfer Langeggweg 3, CH-9500 Wil, Switzerland Updates: see ReSe download page: www.rese.ch/download The MODTRAN R trademark is being used with the expressed permission of the owner, the United States of America, as represented by the United States Air Force. Contents 1 Introduction 11 2 Basic Concepts in the Solar Region 14 2.1 Radiation components................................... 16 2.2 BRDF correction...................................... 19 2.3 Spectral calibration..................................... 21 2.4 Inflight radiometric calibration.............................. 23 2.5 De-shadowing........................................ 24 3 Basic Concepts in the Thermal Region 27 4 Workflow 29 4.1 Menus Overview...................................... 29 4.2 First steps with ATCOR.................................. 31 4.3 Survey of processing steps................................. 34 4.4 Directory structure of ATCOR.............................. 35 4.5 Convention for file names................................. 35 4.6 User-defined hyperspectral sensors............................ 37 4.6.1 Definition of a new sensor............................. 37 4.7 Spectral smile sensors................................... 40 4.8 Haze, cloud, water map.................................. 42 4.9 Processing of multiband thermal data.......................... 43 4.10 External water vapor map................................. 47 5 Description of Modules 48 5.1 Menu: File......................................... 49 5.1.1 Display ENVI File................................. 49 5.1.2 Show Textfile.................................... 52 5.1.3 Select Input Image................................. 52 5.1.4 Import........................................ 52 5.1.5 Plot Sensor Response............................... 53 5.1.6 Plot Calibration File................................ 53 5.1.7 Show System File.................................. 53 5.1.8 Edit Preferences.................................. 54 5.2 Menu: New Sensor..................................... 56 5.2.1 Define Sensor Parameters............................. 57 5.2.2 Create Channel Filter Files............................ 57 5.2.3 BBCALC : Blackbody Function.......................... 59 3 CONTENTS 4 5.2.4 RESLUT : Resample Atm. LUTS from Database................ 59 5.3 Menu: Atm. Correction.................................. 61 5.3.1 The ATCOR main panel.............................. 61 5.3.2 ATCOR2: multispectral sensors, flat terrain................... 61 5.3.3 ATCOR3: multispectral sensors, rugged terrain................. 61 5.3.4 ATCOR2: User-defined Sensors.......................... 62 5.3.5 ATCOR3: User-defined Sensors.......................... 62 5.3.6 SPECTRA module................................. 65 5.3.7 Aerosol Type.................................... 66 5.3.8 Visibility Estimate................................. 66 5.3.9 Inflight radiometric calibration module...................... 66 5.3.10 Shadow removal panels.............................. 69 5.3.11 Panels for Image Processing............................ 72 5.3.12 Start ATCOR Process (Tiled / from ∗.inn)................... 77 5.4 Menu: Topographic..................................... 78 5.4.1 Slope/Aspect.................................... 78 5.4.2 Skyview Factor................................... 78 5.4.3 Shadow Mask.................................... 79 5.4.4 DEM Smoothing.................................. 80 5.5 Menu: Filter........................................ 82 5.5.1 Resample a Spectrum............................... 82 5.5.2 Spectral Polishing: Statistical Filter....................... 82 5.5.3 Spectral Polishing: Radiometric Variation.................... 83 5.5.4 Spectral Smile Interpolation............................ 84 5.6 Menu: Simulation...................................... 87 5.6.1 TOA/At-Sensor Radiance Cube.......................... 87 5.6.2 At-Sensor Apparent Reflectance......................... 87 5.6.3 Resample Image Cube............................... 88 5.7 Menu: Tools......................................... 89 5.7.1 Solar Zenith and Azimuth............................. 89 5.7.2 SPECL: Spectral Reflectance Classification................... 90 5.7.3 SPECL for User Defined Sensors......................... 90 5.7.4 Nadir normalization (Wide FOV Imagery).................... 90 5.7.5 Quick Topographic (no atm.) Correction.................... 91 5.7.6 Add a Blue Spectral Channel........................... 92 5.7.7 Spectral Smile Detection.............................. 92 5.7.8 Spectral Calibration (Atm. Absorption Features)................ 94 5.7.9 Calibration Coefficients with Regression..................... 96 5.7.10 Convert High Res. Database (New Solar Irradiance).............. 97 5.7.11 Convert .atm for another Irradiance Spectrum................. 97 5.8 Menu: Help......................................... 99 5.8.1 Help Options.................................... 99 6 Batch Processing Reference 100 6.1 Using the batch mode................................... 100 6.2 Batch modules, keyword-driven modules......................... 101 CONTENTS 5 7 Value Added Products 108 7.1 LAI, FPAR, Albedo.................................... 108 7.2 Surface energy balance................................... 110 8 Sensor simulation of hyper/multispectral imagery 116 9 Implementation Reference and Sensor Specifics 121 9.1 The Monochromatic atmospheric database........................ 121 9.1.1 Visible / Near Infrared region........................... 121 9.1.2 Thermal region................................... 122 9.1.3 Database update with solar irradiance...................... 123 9.1.4 Sensor-specific atmospheric database....................... 124 9.1.5 Resample sensor-specific atmospheric LUTs with another solar irradiance.. 124 9.2 Supported I/O file types.................................. 125 9.3 Preference parameters for ATCOR............................ 127 9.4 Job control parameters of the "inn" file (former "ini")................. 130 9.5 Problems and Hints.................................... 136 9.6 Metadata files (geometry and calibration)........................ 138 9.6.1 Landsat-7 ETM+................................. 138 9.6.2 SPOT........................................ 139 9.6.3 ALOS AVNIR-2.................................. 141 9.6.4 Ikonos........................................ 141 9.6.5 Quickbird...................................... 142 9.6.6 IRS-1C/1D Liss................................... 143 9.6.7 IRS-P6....................................... 143 9.6.8 ASTER....................................... 143 9.6.9 DMC (Disaster Monitoring Constellation).................... 144 9.6.10 RapidEye...................................... 144 9.6.11 GeoEye-1...................................... 145 9.6.12 WorldView-2.................................... 145 10 Theoretical Background 146 10.1 Basics on radiative transfer................................ 146 10.1.1 Solar spectral region................................ 146 10.1.2 Integrated Radiometric Correction (IRC).................... 153 10.1.3 Spectral solar flux, reflected surface radiance.................. 154 10.1.4 Thermal spectral region.............................. 155 10.2 Masks for haze, cloud, water, snow............................ 159 10.3 Quality layers........................................ 163 10.4 Standard atmospheric conditions............................. 165 10.4.1 Constant visibility (aerosol) and atmospheric water vapor........... 165 10.4.2 Aerosol retrieval and visibility map........................ 166 10.4.3 Water vapor retrieval............................... 171 10.5 Non-standard conditions.................................. 173 10.5.1 Empirical methods for BRDF correction..................... 173 10.5.2 Haze removal over land.............................. 177 10.5.3 Haze or sun glint removal over water....................... 179 10.5.4 Cirrus removal................................... 180 CONTENTS 6 10.5.5 De-shadowing.................................... 183 10.6 Summary of atmospheric correction steps........................ 189 10.6.1 Algorithm for flat terrain............................. 189 10.6.2 Algorithm for rugged terrain........................... 190 10.7 Spectral classification of reflectance cube......................... 191 10.8 Accuracy