Evaluation of the altimetric information from RADARSAT-1, ASTER and SRTM data for topographic mapping in the Amazon Region

Abstract

Brazilian Amazon is a vast territory rich in natural renewable and non-renewable resources. Due to the adverse environmental condition (rain, cloud, dense vegetation, poor access), topographic information is still poor, and when available needs to be up-dated or re-mapped. In this paper, the feasibility of using altimetric information for topographic mapping through orbital stereoscopic (ASTER, RADARSAT-1) and interferometric (SRTM-3) DEMs (digital elevation models) was investigated for two regions in the Brazilian Amazon: Tapajos National Forest (flat terrain) and Serra dos Carajas (mountainous relief). The quality of information produced from these data was evaluated regarding field altimetric measurements. Precise topographic field information acquired from differential global positioning system (DGPS) was used as Ground Control Points (GCPs) for the modeling of the stereoscopic DEMs and as independent check points (ICPs) for the calculation of altimetric accuracies of the products. The investigation has shown that the accuracy of the altimetric information derived from Fine RADARSAT-1, ASTER and SRTM-3 DEMs met the requirements for a semi-detailed (1:100,000-map) scale as requested by the Brazilian standard for cartographic accuracy. Furthermore, SRTM-3 DEM was more accurate than stereoscopic DEMs. The additional great advantage of using SRTM-3 is the free access data. However, up-dated planimetric information is also necessary for cartographic production. Thus it is suggested a combination of altimetry derived for SRTM-3 and planimetry from high-resolution SAR (Fine RADARSAT-1, PALSAR) or if possible optical data (ASTER, SPOT) for topographic mapping at semi-detailed scale in similar environments of the Brazilian Amazon, where terrain information is seldom available or presents low quality.