Abstract
Abstract. End of 2011 a new optical satellite, called Pléiades, was launched by the French space agency (CNES). It provides 20 km x 20 km images at 0.5 meters. This agile acquisition system is able to relocate very rapidly and scan the earth in any direction. The agility of the system offers the ability to acquire multi viewing angle images of the same area during the same orbit. This ability to capture, from a single stereoscopic pair, to a sequence of 25 images, allows enhancing the quality and the completeness of automatically extracted 3D maps. The aim of the study is to validate and quantify the capacity of the Pléiades system to perform 3D mapping. The analysis explores the advantages in terms of quality and automatism to use more than 2 stereoscopic images. In the last 10 years, automatic 3D processing of digital images became more and more popular and efficient. Thanks to aerial images with very large overlap and very high resolution satellite images, new methodologies and algorithms have been implemented to improve the quality and accuracy of automatic 3D processing. We propose to experiment the same type of approaches using Pléiades images to produce digital elevation models (DEM). A focus is made on analysing the 3D processing using video like (multi viewing) acquisitions. Different reference sites with very accurate 3D control points are used to quantify the quality of the Pléiades DEM. Different acquisition modes are explored from a single stereo pair to a sequence of 17 images.
Highlights
The agility of the new generation of earth observation satellites aims at increasing the acquisition capacity, allowing nearby areas to be acquired during the same pass
The interior orientation of the camera was not fully optimised at this time and the results presented here may not reach the ultimate accuracy that will be available when the satellite is officially declared operational
A large number of control points were extracted exclusively on bare earth to avoid the discrepancy between the Pleiades digital elevation models (DEM) and the reference digital terrain model (DTM)
Summary
The agility of the new generation of earth observation satellites aims at increasing the acquisition capacity, allowing nearby areas to be acquired during the same pass. The main motivations are the improvement of the robustness and accuracy, due to the redundancy of the measurements, and the removal of any hidden part in urban area, due to the multiplicity of the viewing angles. Based on these considerations, the applicability of airborne multiview techniques to agile satellites imagery is a worthwhile question. The usual acquisition scheme is based on 60% overlaps in the flight direction with a minimal overlap between adjacent tracks This scheme insures that every point on the ground is seen from, at least, two different points of view, which seems to be sufficient for an open landscape, with moderate slopes and a manual digitizing process. In the case of airborne push-broom cameras like the Leica ADS40/80, a side overlap above 50%
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