Mapping of the spatial-temporal change for vegetation canopy in rough relief areas

Resumo

The purpose of this paper is to present a way of mapping the changes happened in regions with vegetation canopy by means of multiespectral images, using a methodology especially designed for rough relieves, where generally the landforms work as an obstacle for the solar radiation propagation, providing the occurrence of shaded areas. The detection of vegetation areas is not efficient using only techniques as the Normalized Difference Vegetation Index (NDVI). In order to illustrate the mapping proposed technique, it was designed a map that shows the alteration in vegetation cover in the city of Rio de Janeiro whose relief is mostly made up of hills. The set of techniques for determination of vegetation which will overcome the limitations caused by shaded areas is based upon the overlay of the results from the Normalized Difference Vegetation Index (NDVI) and the shaded areas calculated from the Digital Elevation Model (DEM) for verifing the existence of vegetation in regions with low brightness at the moment of the image’s capture by the satellite. Then, it will be possible to verify the existence of vegetation areas even in low illumination regions. These techniques were applied on a series with time interval of ten years using Landsat images considering the period from 1985 to 2015. The combination of the NDVI and DEM images with different insolation directions allowed more consistent results with the vegetation’s reality, reaching more than 97% accuracy. The final product of this work corresponds to a map that identifies the change in vegetation during these 30 years.