Thomas Olsvik Opsahl

• Shimoni, Michal; Idrissa, Mahamadou; Borghys, Dirk; Haavardsholm, Trym Vegard; Opsahl, Thomas Olsvik & Perneel, Christiaan (2017). Urban features classification using 3D hyperspectral data. Workshop on Hyperspectral Image and Signal Processing, Evolution in Remote Sensing. ISSN 2158-6276. 2013-June, p. 1–4. doi: 10.1109/WHISPERS.2013.8080665.
• Morrison, Aiden; Sokolova, Nadezda; Haavardsholm, Trym Vegard; Hagen, Ove Kent; Opsahl, Thomas Olsvik & Ånonsen, Kjetil Bergh (2017). Collaborative indoor navigation for emergency services personnel. IEEE Aerospace Conference. Proceedings. ISSN 1095-323X. 2017-June. doi: 10.1109/AERO.2017.7943729. Show summary

  First responders and other emergency services personnel must often enter buildings which prevent the use of GPS or other satellite navigation signals for positioning. Loss of navigation capability combined with the fact that the buildings are often unknown to the personnel in question makes it more difficult for individual team members to coordinate with one another, and difficult or impossible for the team leader to monitor and direct the actions of each team member. While inertial navigation or pedestrian dead reckoning provide for some degree of navigation in GPS signal denied environments, these solutions degrade with time and may require prohibitively large and expensive inertial solutions to navigate over extended periods, while also allowing each individual user to accumulate independent positioning errors and thereby appearing to ‘drift away’ from one another. This paper presents an implementation of a collaborative navigation system utilizing each of user-to-user radio links, Global Navigation Satellite Systems (GNSS) when available, inertial navigation, pedestrian dead reckoning, as well as camera based Simultaneous Location and Mapping (SLAM) to provide a team of users with absolute and relative situational awareness for themselves and their team. The application of collaborative navigation to such a team provides the triple benefits of providing improved absolute navigation accuracy, improved relative navigation accuracy, and greatly enhanced situational awareness for all cooperating team members.

• (2016). Compact multispectral multi-camera imaging system for small UAVs. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 9840. doi: 10.1117/12.2224495.
• (2014). Characterization of a compact 6-band multifunctional camera based on patterned spectral filters in the focal plane. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 9088. doi: 10.1117/12.2054477.
• Ringaby, Erik; Friman, Ola; Forssén, Per-Erik; Opsahl, Thomas Olsvik; Haavardsholm, Trym Vegard & Kåsen, Ingebjørg (2014). Anisotropic scattered data interpolation for pushbroom image rectification. IEEE Transactions on Image Processing. ISSN 1057-7149. 23(5), p. 2302–2314. doi: 10.1109/TIP.2014.2316377.
• (2014). Compact camera for multispectral and conventional imaging based on patterned filters. Applied Optics. ISSN 1559-128X. p. C64–C71. doi: 10.1364/AO.53.000C64.
• (2013). Estimating the pixel footprint distribution for image fusion by ray tracing lines of sight in a Monte Carlo scheme. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 8743:87431U. doi: 10.1117/12.2015746.
• (2011). Real-time georeferencing for an airborne hyperspectral imaging system. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 8048. doi: 10.1117/12.885069. Show summary

  The paper describes the georeferencing part of an airborne hyperspectral imaging system based on pushbroom scanning. Using ray-tracing methods from computer graphics and a highly efficient representation of the digital elevation model (DEM), georeferencing of high resolution pushbroom images runs in real time by a large margin. By adapting the georeferencing to match the DEM resolution, the camera field of view and the flight altitude, the method has potential to provide real time georeferencing, even for HD video on a high resolution DEM when a graphics processing unit (GPU) is used for processing.

• (2010). An airborne real-time hyperspectral target detection system. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 7695. doi: 10.1117/12.850443. Show summary

  An airborne system for hyperspectral target detection is described. The main sensor is a HySpex pushbroom hyperspectral imager for the visible and near-infrared spectral range with 1600 pixels across track, supplemented by a panchromatic line imager. An optional third sensor can be added, either a SWIR hyperspectral camera or a thermal camera. In real time, the system performs radiometric calibration and georeferencing of the images, followed by image processing for target detection and visualization. The current version of the system implements only spectral anomaly detection, based on normal mixture models. Image processing runs on a PC with a multicore Intel processor and an Nvidia graphics processing unit (GPU). The processing runs in a software framework optimized for large sustained data rates. The platform is a Cessna 172 aircraft based close to FFI, modified with a camera port in the floor.

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• (2018). Compact multispectral multi-camera imaging system for small UAVs.
• Morrison, Aiden; Sokolova, Nadezda; Haavardsholm, Trym Vegard; Hagen, Ove Kent; Opsahl, Thomas Olsvik & Ånonsen, Kjetil Bergh (2017). Collaborative indoor navigation for emergency services personnel.
• Morrison, Aiden; Haavardsholm, Trym Vegard; Hagen, Ove Kent; Opsahl, Thomas Olsvik; Ånonsen, Kjetil Bergh & Eriksen, Erik Holthe (2017). Collaborative Indoor Navigation for Emergency Services Personnel.
• (2013). Multispectral and conventional imaging combined in a compact camera by using patterned filters in the focal plane.
• Resta, Salvatore; Acito, Nicola; Diani, Marco; Corsini, Giovanni; Opsahl, Thomas Olsvik & Haavardsholm, Trym Vegard (2011). Detection of Small Changes in Airborne Hyperspectral Imagery: Experimental Results over Urban Areas.
• (2011). Hyperspectral imaging technology and systems, exemplified by airborne real-time target detection.
• (2010). Real-time direct georeferencing of images from airborne line scan cameras. Show summary

  The Norwegian Defense Research Establishment (FFI) is developing a technology demonstrator for airborne real-time hyperspectral target detection. The system includes two nadir-pointing line scan cameras. The line scanned images are georeferenced in real-time by intersecting rays cast from the cameras with a 3D model of the terrain underneath. The georeferenced images may then easily be ortho-rectified (e.g by using texture mapping in OpenGL) and overlaid digital maps. This poster presents the performance of a cuda implementation of the georeferencing method.

• (2010). Real time direct georeferencing and orthorectification of images from airborne pushbroom cameras.

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