Abstract
Abstract: The positional validation of datasets is an important step for cartography studies since it allows learning about its accuracy, and also indicates the data process quality. However, the positional validation of Synthetic Aperture Radar (SAR) datasets have some additional challenges when compared to optical images due to the geometric distortions. We employ existing targets such as traffic signs and lampposts in the scene and identify them on the image as control points. We performed the validation of the geographic coordinates used as planialtimetric positional control points, using both the amplitude backscattering orthoimage and the Digital Terrain Model (DTM) generated from the InSAR system. We employed the NMAS, ASPRS and NSSDA tests along with information by the Brazilian Standards. This validation showed these control points presented the following results for 1:10,000 scale: NMAS test - class “A” in PEC and PEC-PCD; ASPRS test - RMSE x = 1.317m, RMSE y = 1.231m and RMSE z = 1.145m; and NSSDA test - RMSE r = 1,802m, Precision r = 3.118m and Precision z = 2.244m. These results prove we can use the proposed targets as control points and the used InSAR datasets meet the expected quality for generation of geotechnic products for 1:10,000 scale.
Highlights
The radar system transmits electromagnetic pulses that propagate in space, which, when touching an obstacle, returns to the receiving antenna (Curlander and McDonough 1991; Franceschetti and Lanari 2018), gaining ground for cartography
This system has the following advantages: it is economically viable because of its cloud-view characteristics and can be used at any time of the day and under all weather conditions; it can be used in areas with vegetation, because its signal goes through foliage (Rosa, 2004; Gaboardi and Lübeck, 2016); and it provides the following datasets: Pand X-Band Orthoimages, Color Orthoimages, Digital Surface Model (DSM), and Digital Terrain Model (DTM), which can be utilized in Geotechnics, that uses the cartographic base generated from information as of the orthoimage and the DTM, for the preparation of its thematic maps, for instance, slope maps, shaded reliefs, among others
The planned control points (Figure 9) used in the planialtimetric positional validation did not assume that the entire pixel was at the same coordinate, but that each part of the pixel has its coordinate, as sub-pixels
Summary
The radar system transmits electromagnetic pulses that propagate in space, which, when touching an obstacle (object), returns to the receiving antenna (Curlander and McDonough 1991; Franceschetti and Lanari 2018), gaining ground for cartography This system has the following advantages: it is economically viable because of its cloud-view characteristics and can be used at any time of the day (active sensor) and under all weather conditions; it can be used in areas with vegetation, because its signal goes through foliage (Rosa, 2004; Gaboardi and Lübeck, 2016); and it provides the following datasets: Pand X-Band Orthoimages, Color Orthoimages, Digital Surface Model (DSM), and Digital Terrain Model (DTM), which can be utilized in Geotechnics, that uses the cartographic base generated from information as of the orthoimage and the DTM, for the preparation of its thematic maps, for instance, slope maps, shaded reliefs, among others. This dataset was not positionally validated, it was necessary to verify if it was in accordance with the current Brazilian cartographic norms
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