By adding ground control points, the scene orientation can be optimised, but it is of interest for the user to know the accuracy of a DSM without ground control points, because measuring GCPs is time-consuming and in some remote areas not feasible.In this either study, we focus on the evaluation of DSMs generated with photogrammetric methods by using stereo pairs of airborne ADS80 and spaceborne WorldView-2 images. The data sets are one of the best commercially available images at present and provide potentially valuable high-resolution input data for DSM generation. The Leica Geosystem Airborne Digital Sensor ADS80 was released in 2008 and can deliver stereo co-registered, equal resolution imagery in panchromatic, visible and infrared-bands.
The Digital Globe’s WorldView-2 satellite is operational since 2010 and provides stereo imagery with a panchromatic ground resolution of 0.5 m. As reference for the evaluation of the DSMs ground check point data, stereo-measurements and airborne laser scanning data were used.Hence, the specific aims of this study are:To assess the accuracy of photogrammetric digital surface models based on airborne ADS80 and spaceborne WorldView-2 stereo imagesTo test the influence of bias-corrected rational polynomial coefficients (RPCs) on the accuracy of the WorldView-2 DSMsTo evaluate differences in the accuracy of the derived models based on different land cover types (grass and herb vegetation, forested areas and artificial areas)To discuss the potential of the DSMs for forest applications2.?Material and Methods2.1.
Study AreaThe study area is situated in the eastern part of Switzerland between the two cities of Zurich and Baden (centre image coordinates: 47��25��N and 8��23��E) (Figure 1). The site covers an area of almost 300 km2, with a ground elevation ranging from 339 m to 866 m and is characterised by a hilly topography. A small-scale mixture of different land cover classes (urban, rural and forest) characterises this area, which is typical for the Swiss plateau.Figure 1.Location of the study area in Switzerland between the cities of Zurich and Baden (top, black rectangle). ADS80 CIR image with 11 centrelines of the stripes with 50% overlap in yellow (bottom left) and WorldView-2 scene with the 10 ground control points …2.2. Data for DSM GenerationTwo optical stereo data sets captured in 2010 were used, one acquired by a spaceborne and one AV-951 by an airborne digital sensor.
These data sets formed the basis for the calculation of three different digital surface models (DSMs).2.2.1. WorldView-2 Stereo Satellite ImagesWorldView-2, operational since January 2010, is the first very high-resolution 8-band multispectral commercial satellite providing a ground resolution of truly 0.5 m panchromatic and 1.84 m multispectral. The sensor is able to collect stereo images by looking forward and backward from its actual position [34].