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Unmanned Airborne Systems/Vehicles (UAS/UAV)

UAVs are unmanned aerial vehicles flying automatically using a remote control. Since they can be built-up at very reasonable prices, their use as mapping platform is very cost effective. For mapping they are equipped with small or medium size cameras, while their trajectory is determined using components like an integrated GNSS/INS system (global navigation satellite system / inertial navigation system), a barometric altimeter and a compass.

UAV platforms are used as measuring systems for various mapping and monitoring applications providing a low-cost alternative to the classical manned aerial photogrammetry especially while aiming at large scale mapping for areas of limited extent. Additionally, they open various new applications in the close range domain by combining aerial and terrestrial photogrammetry. One potential application is the fully automatic survey and documentation of digging in open pit mines or stone quarries, which are difficult to access from terrestrial survey. The figure below illustrates a project flown at a quarry close to Vaihingen/Enz.

 

Figure: Quarry at the Photogrammetric Test Site Vaihingen/Enz captured by a UAV flight

In addition to the development of an own workflow for 3D data capture from UAV imagery, the potential of such data was investigated in a pilot project evaluating different UAV platforms and camera systems in a land management application scenario. The following figures show textured 3D surface models from dense image matching. The left example was generated from imagery captured by the low cost consumer-grade compact digital camera Canon IXUS 100 IS, while the right example was captured by the mirrorless interchangeable-lens camera Ricoh GXR Mount A12.

The good accuracy for both flights is demonstrated by the elevation differences determined by the DSMs from the Ricoh and the Canon flight. Obviously, larger differences are limited to vegetated areas like the vineyards. There, the Canon flight on March, which was performed during the leaf-off period in March provided more points on the terrain surface, while the Ricoh flight on August with developed vegetation resulted in more points on that surface. For areas without any change of visible surface geometry, the differences are well below 10cm. Thus the feasibility of relatively simple UAV-platforms and cameras for 3D point determination in the sub-pixel level could be demonstrated.

Figure: DSM differences between Ricoh and Canon flight.

For most of our investigations UAV systems provided as part of cooperation with the Institute of Flight Control and Mechanics (IFR) at the University of Stuttgart were used. Some exemplary platforms are depicted below.

A specific advantage of UAV is their low cruising speed, which allows an image acquisition at considerable overlaps. Such highly overlapping image blocks are not only beneficial during georeferencing, but are especially advantageous while aiming at a dense and accurate image based 3D surface reconstruction as e.g. realized by our matching software SURE. This is also beneficial for applications like urban modeling or the measurement of snow heights. Another current project in cooperation with the Geo-Office GmbH and the Geodetic Institute of Leibniz University Hannover aims at the efficient planning and evaluation of UAV-flights for high accurate capture of building facades.

Figure: UAV application examples urban modelling (left) and measurement of snow heights (right).

 


References

Rothermel, M., Bulatov, D., Haala, N, Wenzel, K. [2014]
Fast and Robust Generation of Semantic Urban Terrain Models from UAV Video Streams, 22nd International Conference on Pattern Recognition

Cramer, M., Haala, N., Gültlinger, M., Hummel, R. [2014]
RPAS im operationellen Einsatz beim LGL Baden-Württemberg – 3D-Dokumentation von Hangrutschungen, DGPF Tagungsband 23 / 2014

Haala, N. & Cramer, M. [2014]
Möglichkeiten und Grenzen der UAV-gestützten photogrammetrischen 3D Datenerfassung, Schriftenreihe des DVW Band 75 / 2014.

Haala, N., Cramer, M. & Rothermel, M. [2013]
Quality of 3D Point clouds from Highly overlapping UAV Imagery. UAV-g 2013. Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XL-1/W2, pp. 183-188.

Cramer, M. [2013]
The UAV@LGL BW Project – A NMCA Case Study. Photogrammetric Week '13, Ed. D. Fritsch, Wichmann, Berlin/Offenbach, pp. 165-179.

Cramer, M., Haala, N., Rothermel, M., Leinss, B. & Fritsch, D. [2013]
UAV@LGL – Pilotstudie zum Einsatz von UAV im Rahmen der Landesvermessung in Deutschland. Photogrammetrie – Fernerkundung – Geoinformation (PFG), Heft 5.

Cramer, M., Haala, N., Rothermel, M., Leinss, B. & Fritsch, D. [2013]
UAV-gestützte Datenerfassung für Anwendungen der Landesvermessung – das Hessigheim-Projekt Tagungsband Vorträge 33. Wissenschaftlich-technische Jahrestagung DGPF, Publikationen der Deutschen Gesellschaft für Photogrammetrie, Fernerkundung und Geoinformation (DGPF) e.V. Band 22, Seite 450-469, Hrsg.: Eckhardt Seyfert.

Haala, N. & Rothermel, M. [2012]
Dense Multiple Stereo Matching of Highly Overlapping UAV Imagery, The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol. XXXIX Part B1, p. 387-392, Commission I, XXIIth ISPRS Congress 2012, Melbourne, Australia, 2012.
http://dx.doi.org/10.5194/isprsarchives-XXXIX-B1-387-2012