A desktop image processing and photogrammetric method for rapid volcanic hazard mapping: application to air-photo interpretation of Mount Pelée, Martinique
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A desktop image processing and photogrammetric method was developed for digitizing black-and-white aerial photographs. The technique was applied to airborne optical images of Mt. Pelée, Martinique, a historically active volcano in the tropical Lesser Antilles island arc, to evaluate its utility for rapid geologic mapping and hazard assessment in vegetated areas. The digital approach provides several advantages over traditional air-photo interpretation by allowing for change detection in time-series images, morphologic characterization, development of digital elevation models from stereopairs, and geo-referencing with other digital data sets. A digital mosaic of Mt. Pelée was created from air photos acquired in 1951, which covered the region affected by the 1902 eruption. Severe mismatches occurred along edges of adjacent photographs prior to correction, which precluded quantitative morphologic analysis of the volcanic edifice. Geometric corrections and histogram equalization of digitized air photos allowed creation of a continuous mosaic. Comparison of the mosaic and a map based on differences in gray scale and texture to a volcanostratigraphic map revealed that not only the various deposits produced during the 1902 event were easily differentiated, but that older eruptive products were identified, suggesting that this approach may be used for rapid hazard evaluation of historically active tropical volcanoes.
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