Analise variografica e processamento digital de imagens aplicados a area da suite intrusiva de Itu(SP)

AUTOR(ES)
DATA DE PUBLICAÇÃO

1994

RESUMO

In this paper a new algorithm of textural characterisation of images by variograms is presented which allies progress achieved by previous methods with innumerable operational facilities, such as the selection of the type of variogram to be calculated, the immediate relationship between the structure observed in the variogram and the dimension of the windows utilised in the classification process and the possibility of utilisation of different algorithms of supervised classification, thanks to the generation of textural bandas which may be processed in any available digital system. The Granitic Suite of!tu was used as a study area, its geological characteristics being integrated by a Geographical Information System for the selection of areas of greater mineral potential. Previsional diagrams based on geochemical and geophysical data permitted the reduction of the area to be prospected by 16 % of the total exposure of the Suite, with a margin of sucess of 70 % on all known occurrences in the area (5/7). The digital processing of the Landsat TM images did not produce good results, mainly due to the intensive human occupation, the vegetation cover, the reduced dimensions of mineral occurrences with no regions with expressive hydrotermal alteration, and the heterogeneities marked by the images. The inclusion of textural bands in the algorithm of classification increases the rigour of class selection, increasing the number of non-classified pixels and reducing the number of the badly classified pixels. For a classification supervised with the maxuer on the original bandas and the textural bandas generated from the TM 7 band, the ratio of erroneously classified pixels was reduced from 22.1 to 8.5 % . However, no distinctive radiometric/textural characteristics ofthe granitic fades were identified. Identical results were observed for the areas of greater prospective potential as well as for the known mineral occurrences

ASSUNTO(S)

mapeamento geologico - itu(sp) geologia - sensoriamento remoto processamento de imagens - tecnicas digitais

ACESSO AO ARTIGO

Documentos Relacionados