ANALYSIS OF NDVI, SAVI AND MSAVI2 INDICES IN FUNCTION WITH THE HEIGHT OF THE TERRAIN IN CRESPO, ENTRE RIOS

Abstract

The advances in geospatial technology, remote sensing, geographical information systems and GPS have made possible new and numerous analysis of digital elevation models (DEM) and the images obtained by remote sensing. The vegetation indices obtained from the images and the DEM products allow progress in the understanding of the interaction between these indices and the characteristics of the terrain. The objective of the present work is the verification of the behavior of the NDVI, SAVI and MSAVI2 indices depending on the height of the ground in the area covered by the topographic map of the IGN (sheet number 3360- 3-1; Scale: 1:50000), to the south of the Department of Paraná in the Province of Entre Ríos (Argentina). The digital elevation model was developed from the level curves of the digitised topographic Charter. The terrain was categorized as low, medium and high according to 3 class intervals close to 33% each. The vegetation indices were obtained from the Operational Land Imager (OLI) sensor of Landsat 8 for the 22nd of February 2016. For the analysis of the vegetation indices, in the different categories of height, 30 polygons of land were vectorised as training sites that - according to their photointerpretation - correspond to batches with crops. With these polygons data is extracted from the indices for statistical analysis. A test was conducted to check the differences in the averages of the samples in the 3 classes. The results indicate that there are significant differences (n = 30, p <0.05) between the mean NDVI of different categories of DEM. On the other hand the SAVI and MSAVI2 indices show no significant difference when the middle and upper categories are analyzed. It was found that the highest values of 3 indices correspond to higher height values related to DEM. In turn, the lowest rates were in areas of lower altitude. It is concluded that in the study area and for summer crops, NDVI, SAVI and MSAVI2 indices could be affected by terrain height.