An assessment of the use of RADARSAT-2 for detailed topographic mapping in a tropical semiarid terrain of Brazil

Abstract

In this paper, the feasibility of using planialtimetric information derived from RADARSAT-2 (RST-2) ultra-fine (UF) stereo pairs and fine quad-pol (FQP) images for detailed topographic mapping was investigated for a semiarid terrain in the Curaçá Valley, northeast of Brazil. Precise topographic field information acquired from a global positioning system was used for ground control points for the modeling of the stereoscopic digital surface models (DSMs), ortho-images, and as independent check points for the calculation of planialtimetric accuracies. The analysis was performed with the following two approaches: (i) the use of root mean square error for the overall classification of the DSMs and ortho-images considering the Brazilian Map Accuracy Standard limits, and (ii) calculations of systematic errors (bias) and accuracy based on a methodology that takes into account computed discrepancies and standard deviations. Thematic information was extracted from FQP data through the use of an unsupervised terrain and land-use classification scheme based on the Freeman–Durden decomposition and the Wishart classifier. The investigation showed that the planialtimetric accuracies of UF DSMs and ortho-images and the thematic information of the FQP data fulfilled the requirements compatible to detailed topographic mapping (1:50000). Thus, the use of RST-2 data can be considered a real alternative as a primary source for detailed topographic mapping programs in similar environments of Brazil, where terrain information is limited or of a poor quality.