Digital stereoscopic and hyperspectral data for environmental mapping applications
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Environmental mapping requires elements of both topographic and thematic mapping. Therefore, both the accuracy specifications for topographic mapping and the classification requirements for thematic mapping must be satisfied. With the increasing number of possible sources of remote sensing image data suitable for environmental mapping, it is important for scientists to fully appreciate the suitability of digital images before embarking on a costly mapping project. This dissertation evaluates the possibilities for deriving elevations by stereocorrelation from stereoscopic image data recorded by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and for creating thematic maps of wetland areas using automated classification techniques with hyperspectral images produced by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). Validation of the digital elevation models (DEMs) created from ASTER stereo data for four study areas in Japan, South America and the United States indicated that, given ASTER image data of good quality and adequate ground control, DEMs can be expected have errors of about 7 to 15 m. Consequently, the ASTER stereo images should prove suitable for topographic mapping of high relief areas at scales of 1:50,000 to 1:100,000 with contour intervals of 40 m or greater. Evaluations of the suitability of AVIRIS hyperspectral data of the Madeira Bay study area at the southern tip of the Everglades National Park in Florida for the construction of a wetland vegetation map at the community and species levels indicated that it is possible to differentiate vegetation communities such as red (Rhizophora mangle L.), black (Avicennia germinans (L.) L.) and white (Laguncularia racemosa (L.) Gaertn. f.) mangrove forests and herbaceous/graminoid prairies. In addition, the high spectral resolution of hyperspectral data enabled the detection (100 percent correctly identified) of an invasive exotic species, lather leaf (Colubrina asiatica (L.) Brongn.), which was otherwise difficult to differentiate on the conventional color infrared photos. This finding implies that early detection of invasive exotics may be possible using automated classification of hyperspectral data. It is anticipated that, in combination, digital stereo images and hyperspectral image data offer potential for improvements in environmental mapping as required for monitoring, modeling and managing Earth resources.