Constructing a digital topographical database (1:1.000.000) for state of São Paulo with RADARSAT-1 data

Abstract

RADARSAT-1 topographical data were fed into a topographical database of the state of São Paulo for geoprocessing in 1:1,000,000 scale. The process consisted of georeferencing, correction of artifacts and evaluation of planimetric and altimetric accuracy. The topographical digital database was structured in a 0.005^o resolution grid. Image artifacts, related to the presence of antenna towers, were observed in the west of São Paulo and a method of digital processing was successfully developed for their suppression. The resulting altimetric images presented mean positional error less than 2km. The mean altimetric error (around 75m), calculated by cartographically sampling elevation data, was explained by the combination of the positional errors with the slope angle distribution, among other effects. Despite a slight data dispersion, the correlation between the elevation of both image and topographical maps, with determination coefficient of r²=0.90, did not indicate the need for systematic fits on the images.