Geo-atmospheric processing of airborne imaging spectrometry data. Part 2: Atmospheric/topographic correction

TLDR

The processing pipeline first geocodes and orthorectifies the scene to obtain per‑pixel view geometry, then applies a combined atmospheric and topographic correction using look‑up tables of radiative transfer functions and a digital elevation model, and is designed to support all common airborne optical instruments from panchromatic to hyperspectral. The method achieves 1–3 % reflectance accuracy, as shown by comparisons with ground measurements, and its database size and accuracy requirements are critically evaluated, with examples of flat and rugged terrain processing.

Abstract

A method for the radiometric correction of wide field-of-view airborne imagery has been developed that accounts for the angular dependence of the path radiance and atmospheric transmittance functions to remove atmospheric and topographic effects. The first part of processing is the parametric geocoding of the scene to obtain a geocoded, orthorectified image and the view geometry (scan and azimuth angles) for each pixel as described in part 1 of this jointly submitted paper. The second part of the processing performs the combined atmospheric/ topographic correction. It uses a database of look-up tables of the atmospheric correction functions (path radiance, atmospheric transmittance, direct and diffuse solar flux) calculated with a radiative transfer code. Additionally, the terrain shape obtained from a digital elevation model is taken into account. The issues of the database size and accuracy requirements are critically discussed. The method supports all common types of imaging airborne optical instruments: panchromatic, multispectral and hyperspectral, including fore/aft tilt sensors covering the wavelength range 0.35-2.55 w m and 8-14 w m. The processor is designed and optimized for imaging spectrometer data. Examples of processing of hyperspectral imagery in flat and rugged terrain are presented. A comparison of ground reflectance measurements with surface reflectance spectra derived from airborne imagery demonstrates that an accuracy of 1-3% reflectance units can be achieved.