AVALIAÇÃO DE TÉCNICA SEMI-SUPERVISIONADA DE ANÁLISE DE VETOR COMPRIMIDO (C2VA) EM IMAGENS DE SATÉLITES PARA DETECÇÃO DE MUDANÇAS DE USO E COBERTURA DA TERRA
Sensoriamento remoto; Análise de mudanças no uso e cobertura do solo; Procesamento de imagens; Análise de vetor de mudanças; Fuzzy C-means
Remote sensing image databases and Geographical Information System have the potential to act as accurate tools for environmental monitoring. Carajas Mountains are an important mineral deposit in Brazil and as environmental laws protect a great portion of this region, they have been at the core of conflicts involving human and nature interests. The biggest mining project in Brazil is active in this region (Carajas project) and this analysis aims at identifying the environmental impact caused directly or indirectly by this activity using state of the art methods. This study collects information of land-use and land-coverage from an area larger than 111 000km2 including five municipalities, aiming at observing the landscape intervention from a big scale perspective as a counterpoint to other studies which are focused on a particular region, such as watersheds. Therefore, employing the resultant products of the multi-spectral approach called Compressed Change Vector Analysis, this work analyses both the environmental changes in each studied municipality of the Carajas Mountains and the environmental counterpart of the company that runs the mining activity. The results show that in general the vegetative coverage was replaced by pasture lands, which in turn were replaced by urban occupations. The comparison with official statistics indicates good accuracy of the present study in the estimation of vegetative cover, although the authors claim that the official methodology can produce inaccurate percentages, probably due to the decrease of spatial resolution from 30 to 60 meters, which affects the minimum size of the identified polygons. The presence of environmentally protected areas has prevented the increase of deforestation in the mountains, in which the observed change rates were at least 15% lower than non-protected regions.