Laser Scanning Survey in the Pl vlgy Cave, Budapest M. Gede 1 , C. - PowerPoint PPT Presentation

Laser Scanning Survey in the Pál ‐ völgy Cave, Budapest M. Gede 1 , C. Petters 2 , G. Nagy 3 , A. Nagy 4 , 1 , B. Kovács 1 , Cs. Egri 5 J. Mészáros 1 Department of Cartography and Geoinformatics, Eötvös Loránd University, Hungary 2 Institue for Cartography, TU Dresden / FARO Europe, Germany 3 Faculty of Geoinformatics University of West Hungary, Székesfehérvár, Hungary 4 GeoLink3D Ltd., Budapest, Hungary 5 Ministry of Rural Development, Department of National Parks and Protected Landscapes, Budapest, Hungary

Outline About the cave Problems of cave surveying Equipment The survey Results Conclusions Further plans

About the cave Budapest – the capital of caves (~100 caves under the town) The Pál ‐ völgy Cave ‐ with recently found connections to neigbouring caves – is part fo the longest cave system in Hungary (28 km) Only 600m is open to the public (with pavement, handrails etc.) Why this cave? ‐ Easily accessible ‐ The survey of the public parts can be finished in one day

Problems of cave surveying Underground work – no GPS, no GSM network  , darkness, ‐ communication problems ‐ Humidity – not perfect conditions for measuring instruments ‐ Hard terrain (in undeveloped caves) ‐ Visitors (developed caves, open to the public) ‐ Traditional survey (gyrocompass, tape measure) – uncertain, big errors ‐ Survey with a total station – not suitable for complex ‐ shaped chambers ‐ Terrestrial laser scanning – good, fast, but the equipment is expensive and vulnerable; processing of resulting point clouds requires high ‐ performace computers

Equipment Our university does not own a TLS; Help from a partner university and a No financial support for the project private company of former students Leica ScanStation C10 Faro Focus 3D (GeoLink3D Ltd.) (Univ. of West Hungary) Spectra Epoch RTK GPS for measuring outer control points

The survey ––– „Leica parts” ––– „Faro parts”

Results Website with scanner panoramas and overview map Flash panorama viewer OpenLayers overview map

Results Point cloud of developed parts 210m 200m 190m 180m 170m

Results Fly ‐ through videos

Results Vector map of pavements, stairs, handrails based on the point cloud Serious accuracy issues of the old map

Conclusions Advantages of Faro Focus3D: ‐ Faster scanning ‐ Smaller weight and size ‐ Automatic recognition of control spheres Advantages of Leica ScanStation C10: ‐ Longer range ‐ Fewer control points (automatically finds vertical axis) When surveying in caves without large chambers the Faro scanner is much more suitable.

Further plans ‐ The compilation of a new, much more accurate map of the cave (in progress) ‐ Creating simplified 3D surface model of the cave ‐ Examining the use of control spheres instead of discs for the Leica system (to speed up the surveying) ‐ Scanning additional parts of the Pál ‐ völgy Cave (where the circumstances make it possible, the scanning scenes have to be approachable by considerably wide corridors to ensure that the instruments can be carried in safely) ‐ Scanning other Hungarian caves. The most promising plan is to survey in the Baradla Cave in North ‐ Eastern Hungary, where huge halls follow each other for several kilometers. The wide corridors and the large sizes make this cave an ideal subject for a TLS survey.

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