DIRECT EXPANSION METHOD FOR ESTIMATING SOYBEAN AND CORN AREA THROUGH MULTITEMPORAL AND ESPECTRAL LANDSAT TM DATA

The purpose of this work was to analyse the contribution of LANDSAT/TM data to estimate soybean and corn areas through direct expansion meth od 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 1:100,0 00 dates Feb. 01, 1989 and Apr. 06, 1989 were utilized using visual in terpretation. The methodology employed consisted in identifing and map ping soybean and corn areas inside 135 sampling units, stratified acco rding to land use criterion. Soybean and corn areas were estimated usi ng the statistical direct expansion method. The results obtained in th is procedure allowed to conclude that: a) the methodology employed to estimate crops area could be utilized in regions where there are not a erial photographs or where these are ancient ones. Thus, this fact wou ld make difficult the use of IBGE direct expansion method (ground trut h collection), and, b) the used methodology in this research was profi table but it presents limitations related with crop types and selectio n of correct period of satellite images.