@article{BecherVoelkerRodehorstetal.,
  author    = {Becher, Lia and V{\"o}lker, Conrad and Rodehorst, Volker and Kuhne, Michael},
  title     = {Background-oriented schlieren technique for two-dimensional visualization of convective indoor air flows},
  series = {Optics and Lasers in Engineering},
  volume    = {2020},
  journal   = {Optics and Lasers in Engineering},
  number    = {Volume 134, article 106282},
  doi       = {https://doi.org/10.1016/j.optlaseng.2020.106282},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220810-46972},
  pages     = {9},
  abstract  = {This article focuses on further developments of the background-oriented schlieren (BOS) technique to visualize convective indoor air flow, which is usually defined by very small density gradients. Since the light rays deflect when passing through fluids with different densities, BOS can detect the resulting refractive index gradients as integration along a line of sight. In this paper, the BOS technique is used to yield a two-dimensional visualization of small density gradients. The novelty of the described method is the implementation of a highly sensitive BOS setup to visualize the ascending thermal plume from a heated thermal manikin with temperature differences of minimum 1 K. To guarantee steady boundary conditions, the thermal manikin was seated in a climate laboratory. For the experimental investigations, a high-resolution DLSR camera was used capturing a large field of view with sufficient detail accuracy. Several parameters such as various backgrounds, focal lengths, room air temperatures, and distances between the object of investigation, camera, and structured background were tested to find the most suitable parameters to visualize convective indoor air flow. Besides these measurements, this paper presents the analyzing method using cross-correlation algorithms and finally the results of visualizing the convective indoor air flow with BOS. The highly sensitive BOS setup presented in this article complements the commonly used invasive methods that highly influence weak air flows.},
  subject      = {Raumklima},
  language  = {en}
}
@inproceedings{PaulRodehorst,
  author    = {Paul, Debus and Rodehorst, Volker},
  title     = {Multi-Scale Flight Path Planning for UAS Building Inspection},
  series = {Proceedings of the 18th International Conference on Computing in Civil and Building Engineering},
  volume    = {2020},
  booktitle = {Proceedings of the 18th International Conference on Computing in Civil and Building Engineering},
  editor    = {Santos, Toledo},
  publisher = {Springer},
  doi       = {10.25643/bauhaus-universitaet.4205},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20201009-42053},
  pages     = {19},
  abstract  = {Unmanned aircraft systems (UAS) show large potential for the construction industry. Their use in condition assessment has increased significantly, due to technological and computational progress. UAS play a crucial role in developing a digital maintenance strategy for infrastructure, saving cost and effort, while increasing safety and reliability. Part of that strategy are automated visual UAS inspections of the building's condition. The resulting images can automatically be analyzed to identify and localize damages to the structure that have to be monitored. Further interest in parts of a structure can arise from events like accidents or collisions. Areas of low interest exist, where low resolution monitoring is sufficient. From different requirements for resolution, different levels of detail can be derived. They require special image acquisition parameters that differ mainly in the distance between camera and structure. Areas with a higher level of detail require a smaller distance to the object, producing more images. This work proposes a multi-scale flight path planning procedure, enabling higher resolution requirements for areas of special interest, while reducing the number of required images to a minimum. Careful selection of the camera positions maintains the complete coverage of the structure, while achieving the required resolution in all areas. The result is an efficient UAS inspection, reducing effort for the maintenance of infrastructure.},
  subject      = {Drohne},
  language  = {en}
}
@inproceedings{Rodehorst,
  author    = {Rodehorst, Volker},
  title     = {EVALUATION OF THE METRIC TRIFOCAL TENSOR FOR RELATIVE THREE-VIEW ORIENTATION},
  series = {Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 20 - 22 2015, Bauhaus-University Weimar},
  booktitle = {Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 20 - 22 2015, Bauhaus-University Weimar},
  editor    = {G{\"u}rlebeck, Klaus and Lahmer, Tom},
  organization    = {Bauhaus-Universit{\"a}t Weimar},
  issn      = {1611-4086},
  doi       = {10.25643/bauhaus-universitaet.2817},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20170314-28178},
  pages     = {7},
  abstract  = {In photogrammetry and computer vision the trifocal tensor is used to describe the geometric relation between projections of points in three views. In this paper we analyze the stability and accuracy of the metric trifocal tensor for calibrated cameras. Since a minimal parameterization of the metric trifocal tensor is challenging, the additional constraints of the interior orientation are applied to the well-known projective 6-point and 7-point algorithms for three images. The experimental results show that the linear 7-point algorithm fails for some noise-free degenerated cases, whereas the minimal 6-point algorithm seems to be competitive even with realistic noise.},
  subject      = {Angewandte Informatik},
  language  = {en}
}
@inproceedings{KerstenRodehorst,
  author    = {Kersten, Jens and Rodehorst, Volker},
  title     = {TOWARDS STEREO VISION- AND LASER SCANNER-BASED UAS POSE ESTIMATION},
  series = {Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 20 - 22 2015, Bauhaus-University Weimar},
  booktitle = {Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 20 - 22 2015, Bauhaus-University Weimar},
  editor    = {G{\"u}rlebeck, Klaus and Lahmer, Tom},
  organization    = {Bauhaus-Universit{\"a}t Weimar},
  issn      = {1611-4086},
  doi       = {10.25643/bauhaus-universitaet.2807},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20170314-28072},
  pages     = {7},
  abstract  = {A central issue for the autonomous navigation of mobile robots is to map unknown environments while simultaneously estimating its position within this map. This chicken-eggproblem is known as simultaneous localization and mapping (SLAM). Asctec's quadrotor Pelican is a powerful and flexible research UAS (unmanned aircraft system) which enables the development of new real-time on-board algorithms for SLAM as well as autonomous navigation. The relative UAS pose estimation for SLAM, usually based on low-cost sensors like inertial measurement units (IMU) and barometers, is known to be affected by high drift rates. In order to significantly reduce these effects, we incorporate additional independent pose estimation techniques using exteroceptive sensors. In this article we present first pose estimation results using a stereo camera setup as well as a laser range finder, individually. Even though these methods fail in few certain configurations we demonstrate their effectiveness and value for the reduction of IMU drift rates and give an outlook for further works towards SLAM.},
  subject      = {Angewandte Informatik},
  language  = {en}
}