Resumo

O monitoramento preciso de corpos d’água é fundamental para a gestão de recursos hídricos e o desenvolvimento sustentável da aquicultura, especialmente em regiões semiáridas. Este estudo avaliou o desempenho de diferentes índices espectrais de água (NDWI, MNDWI, NWI, AWEIsh, AWEInsh e SWI) aplicados a imagens Landsat 8 OLI para a identificação automática de viveiros voltados à carcinicultura no município de Aracati, Ceará. A classificação binária dos índices espectrais, calculados a partir das bandas processadas no QGIS, foi realizada por meio do método de Otsu, aplicado de maneira independente às duas áreas de interesse: a cena completa e o recorte restrito aos viveiros aquícolas. O desempenho foi analisado tanto para uma cena maior, que inclui diferentes usos do solo, quanto para um recorte restrito à área dos viveiros. Os resultados evidenciaram que a utilização de áreas homogêneas favorece a segmentação espectral entre água e áreas secas, otimizando a aplicação de limiares automáticos. Entre os índices testados, o NWI apresentou o melhor desempenho na separação dos alvos, seguido por MNDWI e NDWI, enquanto índices subtrativos como AWEIsh, AWEInsh e SWI apresentaram limitações devido à sensibilidade a sombras e superfícies úmidas não aquáticas. A análise dos histogramas e estatísticas descritivas confirmou que ambientes mais homogêneos e índices com distribuição bimodal clara maximizam a eficácia do método de Otsu. O estudo destaca ainda a importância de abordagens adaptativas em áreas espectralmente complexas e recomenda o uso de séries temporais, imagens de maior resolução e técnicas de inteligência artificial em futuras pesquisas para aprimorar a acurácia do mapeamento aquícola e de recursos hídricos.

Palavras-chave

• sensoriamento remoto
• índice de água
• carcinicultura
• segmentação espectral
• algoritmo Otsu

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