Abstract
Abstract. Conducted in the City of Tshwane, South Africa, this study set about to test the accuracy of DSMs derived from different remotely sensed data locally. VHR digital mapping camera stereo-pairs, tri-stereo imagery collected by a Pléiades satellite and data detected from the Tandem-X InSAR satellite configuration were fundamental in the construction of seamless DSM products at different postings, namely 2 m, 4 m and 12 m. The three DSMs were sampled against independent control points originating from validated airborne LiDAR data. The reference surfaces were derived from the same dense point cloud at grid resolutions corresponding to those of the samples. The absolute and relative positional accuracies were computed using well-known DEM error metrics and accuracy statistics. Overall vertical accuracies were also assessed and compared across seven slope classes and nine primary land cover classes. Although all three DSMs displayed significantly more vertical errors where solid waterbodies, dense natural and/or alien woody vegetation and, in a lesser degree, urban residential areas with significant canopy cover were encountered, all three surpassed their expected positional accuracies overall.
Highlights
The digital representation of the Earth’s topographic surface as a regular grid amplified with diverse vegetation, manmade features and bare terrain seamlessly manifested as elevation values have become commonplace in the modern digital era
With the overall expected accuracy descriptor stated for each DSM across all land cover classes, it was clear that all three sample products performed very well
The same pattern can be observed across all three DSMs, which indicates that it remains challenging to model these complex surfaces with current remote sensing (RS) technology
Summary
The digital representation of the Earth’s topographic surface as a regular grid amplified with diverse vegetation, manmade features and bare terrain seamlessly manifested as elevation values have become commonplace in the modern digital era. Enabled by remote sensing (RS) technology used in Earth Observation in particular, one can appreciate and visualise familiarities in the approximated landscapes, in most cases even right up to your own neighbourhood or doorstep This feat is technically supported and enhanced far by a DEM, nowadays covering the entire Earth and can be of truly remarkable quality. Used to correspond to terrain relief, a DEM is a digital representation of continuous elevation values over a topographic surface by a regular array of x, y, and z values, all referenced to a common datum. The edited first stage DSM represents a continuous land surface that includes the elevation or orthometric height (in meters) of projected off-terrain objects such as buildings and vegetation, locally referenced to mean sea level (MSL). The main production challenges faced here normally are to preserve the scale characteristics of different DEM (Poli et al, 2009) whilst preserving terrain continuity (Doytsher et al, 2009)
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