Avaliação de Critérios de Seleção de Atributos Espectrais de Imagens Digitais MSS - LANDSAT em Discriminações Litológicas no Baixo Vale do Rio Curaçá, BA

Abstract

The use of spectral attributes criteria was investigated, based on measures of statistical distance of separability between thematic classes in MSS digital LANDSAT imagery, in order to select the best subsets of channels in composite colors for the detection and discrimination of lithological units in the lower Valley of Curaçá River, State of Bahia. Two selection criteria were used based on representative sampling pixels of thematic classes related to lithologic units: a) maximization of the average distance among the JM2 Distance for all pairs of classes, b) maximization of minimum JM2 Distance among the pairs of classes. The analysis was restricted only to digital MSS data from the dry season and three situations were investigated: a) selection of the three best channels, considering the four original channels (channels 4, 5, 6 and 7); b) selection of the three best channels, considering the six MSS ratios (channels 4/5, 4/6, 4/7, 5/6, 5/7 and 6/7); and c) selection of the three best channels in a hybrid approach (the four original channels and the six ratios). A visual analysis was done on color composite images using the selected sets and based on detection and discrimination indices of ranking. The research showed that the hybrid product (channels 4, 5/7 and 7 with green, blue and red, respectively) and the Normal Color Composite (channels, 4, 5 and 7 with blue, green and red colors, respectively) had the best performance. The ratio products, on the other hand, presented great ambiguities.