Índice Físico (NVDI) aplicado na análise da cobertura vegetal do Parque Nacional das Nascentes do rio Parnaíba

Abstract

The Objective of this study was to apply the normalized difference vegetation index (NDVI) in the vegetation cover analysis in the Nascentes of Rio Parnaíba National Park, in the urban perimeter of the County of Corrente-PI. It used band 3, which corresponds to the band of the Red Visible and band 4, corresponding to the Near Infrared band in the electromagnetic spectrum. The calculation of the NDVI is made from the difference between bands 3 and 4, of the satellite Landsat-05, sensor TM (Thematic Mapper), divided by the sum of the two bands. The result varies from -1 to 1, so that the closer to 1, the greater the presence of vegetation, and the closer to -1, the greater the presence of exposed soils and rocks. For the calculation of NDVI and maps to present the results, the free and free software - Geographic Information System (GIS), Quantum GIS 2.4.0 was used. The procedures for calculating NDVI were: initially through the add raster image command, where the Landsat images corresponding to Bands 3 and 4 were inserted; Then to perform the NDVI calculation the Raster menu was accessed, and in the window that opens enter the formula in the raster calculator: Float (band 4 - band 3) / float (band 4 + band 3). From the analyzes it can be observed that the year 1995 and the months of August and November 2005 were the ones with the lowest NDVI value, showing that in those years there was a higher index of the presence of exposed soils due to the lack of coverage Caused by natural actions and anthropic activities in the area. For the year 2000 and the months of February to May 2010 the values were between 0.56 to 0.62 μm, characterized by the presence of vegetation, being proved by the NDVI result, through the shades of green.