06 Fakultät Luft- und Raumfahrttechnik und Geodäsie
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/7
Browse
4 results
Search Results
Item Open Access Automation in laser scanning for cultural heritage applications(2005) Böhm, Jan; Haala, Norbert; Alshawabkeh, YahyaWithin the paper we present the current activities of the Institute for Photogrammetry in cultural heritage documentation in Jordan. In particular two sites, Petra and Jerash, were recorded using terrestrial laser scanning (TLS). We present the results and the current status of the recording. Experiences drawn from these projects have led us to investigate more automated approaches to TLS data processing. We detail two approaches within this work. The automation of georeferencing for TLS data is presented along with our approach for automated feature extraction.Item Open Access Radargrammetric DSM generation by semi-global matching and evaluation of penalty functions(2022) Wang, Jinghui; Gong, Ke; Balz, Timo; Haala, Norbert; Sörgel, Uwe; Zhang, Lu; Liao, MingshengRadargrammetry is a useful approach to generate Digital Surface Models (DSMs) and an alternative to InSAR techniques that are subject to temporal or atmospheric decorrelation. Stereo image matching in radargrammetry refers to the process of determining homologous points in two images. The performance of image matching influences the final quality of DSM used for spatial-temporal analysis of landscapes and terrain. In SAR image matching, local matching methods are commonly used but usually produce sparse and inaccurate homologous points adding ambiguity to final products; global or semi-global matching methods are seldom applied even though more accurate and dense homologous points can be yielded. To fill this gap, we propose a hierarchical semi-global matching (SGM) pipeline to reconstruct DSMs in forested and mountainous regions using stereo TerraSAR-X images. In addition, three penalty functions were implemented in the pipeline and evaluated for effectiveness. To make accuracy and efficiency comparisons between our SGM dense matching method and the local matching method, the normalized cross-correlation (NCC) local matching method was also applied to generate DSMs using the same test data. The accuracy of radargrammetric DSMs was validated against an airborne photogrammetric reference DSM and compared with the accuracy of NASA’s 30 m SRTM DEM. The results show the SGM pipeline produces DSMs with height accuracy and computing efficiency that exceeds the SRTM DEM and NCC-derived DSMs. The penalty function adopting the Canny edge detector yields a higher vertical precision than the other two evaluated penalty functions. SGM is a powerful and efficient tool to produce high-quality DSMs using stereo Spaceborne SAR images.Item Open Access Efficient integration of aerial and terrestrial laser data for virtual city modeling uUsing LASERMAPs(2005) Böhm, Jan; Haala, NorbertOne of the first steps during evaluation of terrestrial LIDAR measurement is the co-registration of the data sets, which are collected from different stations and their transformation to a suitable reference coordinate system. As it is demonstrated within the paper, this can be achieved automatically, if low-cost components are used for direct georeferencing parallel to LIDAR measurement. By these means the position and orientation of the laser scanner can be determined. Further refinement is feasible, if the terrestrial scans are aligned to a DEM from airborne LIDAR or existing 3D building models. Frequently, terrestrial lasers scanning (TLS) is used to collect building facades at a large amount of geometric detail. For this type of application, the integration of existing 3D building models from airborne data collection as complimentary data source is especially suitable for the modeling step. Due to viewpoint restrictions of airborne data collection, the amount of detail, which is available for the building facades, is very limited. Thus, after alignment, the terrestrial scans are ideally suited to refine these models. However, as it is demonstrated in the second part of the paper, the large effort required for explicit modeling can be avoided if so-called LASERMAPs are extracted from TLS and mapped against the coarse 3D building model.Item Open Access Three- and four-dimensional topographic measurement and validation(2021) Rocca, Fabio; Li, Deren; Tebaldini, Stefano; Liao, Mingsheng; Zhang, Lu; Lombardini, Fabrizio; Balz, Timo; Haala, Norbert; Ding, Xiaoli; Hanssen, RamonThis paper reports on the activities carried out in the context of “Dragon project 32278: Three- and Four-Dimensional Topographic Measurement and Validation”. The research work was split into three subprojects and encompassed several activities to deliver accurate characterization of targets on land surfaces and deepen the current knowledge on the exploitation of Synthetic Aperture Radar (SAR) data. The goal of Subproject 1 was to validate topographic mapping accuracy of various ESA, TPM, and Chinese satellite system on test sites in the EU and China; define and improve validation methodologies for topographic mapping; and develop and setup test sites for the validation of different surface motion estimation techniques. Subproject 2 focused on the specific case of spatially and temporally decorrelating targets by using multi-baseline interferometric (InSAR) and tomographic (TomoSAR) SAR processing. Research on InSAR led to the development of robust retrieval techniques to estimate target displacement over time. Research on TomoSAR was focused on testing or defining new processing methods for high-resolution 3D imaging of the interior of forests and glaciers and the characterization of their temporal behavior. Subproject 3 was focused on near-real-time motion estimation, considering efficient algorithms for the digestion of new acquisitions and for changes in problem parameterization.