Atmospheric effects in satellite imaging of mountainous terrain

Abstract

It is possible to obtain useful maps of surface albedo from remotely sensed images by eliminating effects due to topography and the atmosphere, even when the atmospheric state is not known. A simple phenomenological model of earth radiance that depends on six empirically determined parameters is developed given certain simplifying assumptions. The model incorporates path radiance and illumination from sun and sky and their dependencies on surface altitude and orientation. It takes explicit account of surface shape, represented by a digital terrain model, and is therefore especially suited for use in mountainous terrain. A number of ways of determining the model parameters are discussed, including the use of shadows to obtain path radiance and to estimate local albedo and sky irradiance. The emphasis is on extracting as much information from the image as possible, given a digital terrain model of the imaged area and a minimum of site-specific atmospheric data. The albedo image, introduced as a representation of surface reflectance, provides a useful tool to evaluate the simple imaging model. Criteria for the subjective evaluation of albedo images are established and illustrated for Landsat multispectral data of a mountainous region of Switzerland. The method exposes some of the limitations found in computing reflectance information using only the imageforming equation.

Spatio-temporal analysis of potential aquifer recharge: Application to the Basin of Mexico

“…As a first step, a digital elevation model (DEM) at 30 m resolution was obtained by resampling a 90 m resolution DEM obtained from the Shuttle Radar Topography Mission (SRTM) using the regularized spline with tension and smoothing algorithm of Mitasova and Mitas (1993). This resolution was required as surface albedo maps developed from satellite images need to be corrected for both topographic and atmospheric effects (Sjoberg and Horn, 1983). The SRTM data was also resampled to a 200 m resolution DEM following the same procedure, in order to develop the spatial distribution of Figure 2 Proposed approach to determine the spatio-temporal distribution of potential aquifer recharge in the Basin of Mexico and its use as boundary condition in a regional groundwater flow model.…”

<title>Nonlinear mean-square estimation with applications in remote sensing</title>

“…The approach is based on using information from the infrare d (IR) bands which are not affected by haze to predict the haze-free values of the visible bands. Assume tha t the atmosphere can be modeled as a horizontally homogeneous medium, the earth is a Lambertian reflecto r, and atmospheric properties which vary exponentially with altitude can be assumed to be constant over the scene (Sjoberg and Horn 1983). When the contribution of the ambient illumination (skylight) can be negle cted and scattering is constant over the image, the brightness…”

Digital imagery analysis of unusual Martian surface features

“…The first assumption allows us to reduce a 3-D problem to a 1-D problem [18]. Assumption two is based on observations by Wildey [13] that the winds tend to redeposit surface materials in a uniform fashion so the albedo and scattering properties can be treated as approximately constant over small areas.…”