Direct expansion method for estimating soybean and corn area through multitemporal and espectral LANDSAT/TM1 data

Abstract

The purpose of this work was to analyse the contribution of LANDSAT/TM data to estimate soybean and corn areas through direct expansion method by sampling techniques. The study was carried out in the test site of "Distrito Federal" (5,814 km²), covered by LANDSAT/TM (row/path 221/71) data. The colour composition bands 3,4 and 5, in scale of 1:100,000 dates Feb. 01, 1989 and Apr. 06, 1989 were utilized using visual interpretation. The methodology employed consisted in identifing and mapping soybean and corn areas inside 135 sampling units, stratified according to land use criterion. Soybean and corn areas were estimated using the statistical direct expansion method. The results obtained in this procedure allowed to conclude that: a) the methodology employed to estimate crops area could be utilized in regions where there are not aerial photographs or where these are ancient ones. Thus, this fact would make difficult the use of IBGE direct expansion method (ground truth collection), and, b) the used methodology in this research was profitable but it presents limitations related with crop types and selection of correct period of satellite images.