fusion of laser scanning and photogrammetric data for the documentation and vr … · fusion of...
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||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry
E. Friedli, J. Banz, Z. Gojcic and A. Wieser
10.05.2018FIG Congress 2018 - Istanbul - Turkey 1
Fusion of laser scanning and Photogrammetric
data for the documentation and VR visualization
of an archaeological tomb complex
Presented at th
e FIG Congress 2018,
May 6-11, 2018 in
Ista
nbul, Turkey
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry10.05.2018FIG Congress 2018 - Istanbul - Turkey 2
Life Histories of Theban Tombs (LHTT)1
)1 Cooperation with Department of Ancient Civilizations, University of Basel, SNSF grant 162967, https://lhtt.philhist. unibas.ch/sheikh-abd-el-qurna
Goal: 3D Digital Reality with large coverage
and sub-mm resolution
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry10.05.2018FIG Congress 2018 - Istanbul - Turkey 3
Approach
▪ Fusion of TLS, Photogrammetry and close-up scans
▪ Selective coverage with highest resolution
Fotos: © University of Basel, LHTT Photos: M. Kačičnik
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry
Challenge:
Upper part not accessible with the scanner
Solution:
▪ 8 scans of the shaft (ladder)
▪ 98 pictures with SLR camera
mounted on a long pole for upper ¼
▪ Feature-based registration of
photogrammetric and TLS point clouds
(overlap only 15%)
10.05.2018FIG Congress 2018 - Istanbul - Turkey 4
Example: Narrow vertical shaft
© University of Basel, LHTT Photo: K. Powroznik
10 m
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry10.05.2018FIG Congress 2018 - Istanbul - Turkey 5
Workflow
TLS
point cloud
Photogrammetric
point cloud
Coarse scaling
Keypoint extraction
(Harris3D)
Keypoint matching
(K4-PCS)
Fine alignment
and scaling (ICP)
Registered
point clouds
Coarse alignment
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry10.05.2018FIG Congress 2018 - Istanbul - Turkey 6
Results
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry10.05.2018FIG Congress 2018 - Istanbul - Turkey 7
Results
2 m
vertical
cross section
horizontal
cross section
5 mm RMS
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry
Challenge
Fully textured 3D model
despite poor illumination, surface roughness,
and parts with little texture
Solution
▪ TLS for geometry (80 scans)
▪ RGB pictures (7000) with
SLR camera and flash for texture
▪ Fusion of TLS and photogrammetric point
clouds after color adjustment
and dense matching
10.05.2018FIG Congress 2018 - Istanbul - Turkey 8
Example: Funerary Chapel
© University of Basel, LHTT Map: G. Heindl, S. Stucky
© University of Basel, LHTT Photo: M. Kačičnik
9 m
18 m
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry10.05.2018FIG Congress 2018 - Istanbul - Turkey 9
Workflow 1 (Geometry)
TLS
point cloud
Photogrammetric
point cloud
Coarse scaling
Keypoint extraction
(Harris3D)
Keypoint matching
(K4-PCS)
Fine alignment
and scaling (ICP)
Registered
point clouds
Coarse alignment
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry10.05.2018FIG Congress 2018 - Istanbul - Turkey 10
Workflow 2 (Texture)
TLS
mesh
Oriented and
calibrated images
Creation of
texture atlas
Textured
TLS mesh
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry10.05.2018FIG Congress 2018 - Istanbul - Turkey 11
Texture Atlas
Atlas
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry10.05.2018FIG Congress 2018 - Istanbul - Turkey 12
Workflow 3 (Reduction of resolution)
Challenge:
Resulting textured model too large
for RT visualization (25M faces)
Solution:
▪ Decimation of TLS mesh
▪ Calculation of bump maps
▪ New texture atlas:
Shading from bump map
plus original texture
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry10.05.2018FIG Congress 2018 - Istanbul - Turkey 13
Workflow 3 (Reduction of resolution)
original resolution (25 Mio faces)decimated resolution (22k faces)decimated resolution (22k)
with bump map from the original resolution
||Geosensors and Engineering Geodesy
Institute of Geodesy and Photogrammetry10.05.2018FIG Congress 2018 - Istanbul - Turkey 14
Conclusion
▪ Multi-modal data acquisition
for generation of 3d models
with appropriate properties
▪ Variety of sensors for obtaining
point clouds and colors
▪ Key are coregistration and blending
▪ Presented herein purely data driven
approach for scaling and registration
▪ RT visualization using techniques
from gaming industry and CG