Atmospheric / Topographic Correction for Satellite Imagery

Introduction

Atmospheric and Topographic Correction for Satellite Imagery (ATCOR) is a method used to reduce atmospheric and illumination effects on remote sensed data to retrieve physical parameters of the earth's surface such as atmospheric conditions (emissivity, temperature), thermal and atmospheric radiance and transmittance functions to simulate the simplified properties of a 3D atmosphere.

Left: Scene without ATCOR; Right: Scene with ATCOR

The method is restricted to high spatial resolution satellite sensors like GeoEye-1, WorldView-2,Worldview-1, QuickBird, IKONOS, LANDSAT TM, SPOT-5 and ASTER. The algorithm can be applied to multispectral and panchromatic imagery. The objective of this method is important for analysis in order to:

• Remove or reduce the influence of atmospheric and solar illumination
• Be able to compare multi-temporal satellite images with different times of acquisition. After time atmospheric correction, changes observed are due to different features on the earth's surface rather than differences of the atmospheric condition
• Improve the results of change detection and classification algorithms
• Be able to compare multi-sensor images with similar spectral bands
• To compare ground reflectance data retrieved from satellite imagery to the ground reflectance from measurements in the field

ATCOR method is used for various applications such as:

• Multi-temporal and multi-sensoral land cover classification
• Forest damage monitoring
• Surface temperature mapping
• Harvest estimations
• Erosion monitoring

ATCOR 2 — Correction of Flat Terrain

Schematic sketch of radiation components for a flat terrain (click to enlarge)

Solar Region

Processing of bands consists of the total signal at the sensor by path radiance, reflected radiation from the viewed pixel and radiation from the neighborhood (topological space). The atmospheric condition such as water vapor content, aerosol type and visibility for a scene can be estimated with the SPECTRA module, followed by surface reflectance spectrum of the primary area in the scene which can be viewed as a function of the selected atmospheric parameters.

Thermal Region

Processing of bands by path radiance emitted by the atmosphere between ground and sensor, emitted ground radiance (temperature and Emissivity) and reflected downwelling thermal atmosphere flux. Scattered radiation from the neighborhood is usually neglected in the thermal region due to the scattering efficiency of atmosphere decreases strongly with wavelength.

ATCOR 3 — Mountainous Terrain

Schematic sketch of radiation components for rugged terrain (click to enlarge)

ATCOR3 is atmospheric correction and haze removal software used to correct changes in the spectral reflectance of materials on the earth's surface. ATCOR3 includes all of the capabilities of ATCOR2 and can be integrated with a DEM for atmospheric correction of images depicting rugged terrain.

Features

• Produce sharp and brilliant satellite images
• Reduce the shadow effect in mountainous terrain
• Obtain better classification results by using real reflectance values
• Compare multi-temporal and multi-sensoral values
• Calculate value added products such as sky view factor and cast shadow calculation

Satellite Imaging Corporation utilizes advanced Remote Sensing techniques, Color and Panchromatic image data processing services are provided, including orthorectification, pan sharpening with image data fusion, image enhancements, georeferencing and mosaicing and color/grayscale balancing. Optional satellite imaging features may incorporate specialized processing procedures used to analyze soils, vegetation, water and rock features.

With over a decade of experience in acquiring satellite images and airborne-sensed data, Satellite Imaging Corporation (SIC) provides top quality satellite images and other remote sensing products, Geographic Information System (GIS) projects and consultancy services. Satellite Imaging Corporation is equipped to negotiate for and appropriate high-resolution satellite images, as well as enhance satellite image data to create accurate, interactive mapping projects.

For more information or consultation about ATCOR or any of our other services and products please contact SIC by e-mail or phone us at 832-237-2900.