ÉVALUATION DE SPOT ET SEASAT POUR LA CARTOGRAPHIE DES LINÉAMENTS : COMPARAISON BASÉE SUR L'ANALYSE DE SPECTRES DE FOURIER

Abstract

SUMMARYThe lineaments observed in the SPOT and SEASAT images of the volcano-sedimentary sequence in the Stoke Mountains of the southern Appalachians of Quebec were enhanced using the Sobel-directional gradient filter. Two types of binary images of the lineaments were produced: the first, by digitalsegmentation of the distributions of the two perpendicular directional gradient images; the second, by visual interpretation of a colour composite of the directional-filtered images. The difference between the structural trends identified on SPOT and SEASAT images were represented on the Fourier spectra of the binary images of the lineaments. The SPOT and SEASAT images were compared using statistics extracted from the spectra with two continuous sampling geometries: the 9° directional points and the concentric ring samplings. The results of this analysis demonstrate that the range of lineament orientations was greater on the SPOT imagery. The numerical method enhanced the lineaments included within a range of 130° on the SPOT image, compared with 110° for the SEASAT image. The visual interpretation of the directional gradient images revealed the presence of more circular features and lineaments oriented within the direction of the radiation. The range of structural orientations detected by visual interpretation of the filtered images reached 145° and 135° for the SPOT and SEASAT data, respectively. The angular energy distribution of Fourier spectra also showed the predominance of lineaments with ENE orientation on the SPOT data and N-S on the SEASAT data. A comparative curve representing the definition of the lineaments on the SPOT and SEASAT images with the different potential orientations is presented. In general, the lineaments oriented within N30°E and N120°E were better perceived on the SPOT image, while other structural orientations (N0°E to N30°E and N120°E to N180°E) were better defined by the radar data from SEASAT.