1. Capturing the 3D motion of ski jumpers Trip to Bonn (13-16 Nov 2005) Atle Nes Faculty of Informatics and e-Learning Trondheim University College

2. Project description -Goal: Design a multiple video camera system that can be used to capture and study the motion of ski jumpers in 3D. -Task: Want to give feedback to the ski jumpers that can help them to improve their jumping skills.

3. How? Multiple video cameras placed in a ski jumping hill are used to capture image sequences of a ski jump from different angles synchronously.

4. Image Acquisition (capture video of ski jumper) Video Images Image Processing (detect, identify & track points) 2D Image Coordinates Photogrammetry (2d  3d mapping) 3D Object Coordinates Motion analysis (select & interpret motion data) Vizualization (relate 3d points to ski jump model)

5. Camera equipment 3x AVT Marlin cameras: IEEE-1394 FireWire DCAM Resolution 640x480 x 30 fps x 8 bit grayscale 3x 9 MB/s = 27 MB/s Changeable lenses

6. Camera equipment (cont.) Operating long distances: 3x 400 m optical fibre extension for firewire (signals and data) 3x 25 m power cables 600 m synchronization cable PC: 2.4 GHz Intel P4, 4x Firewire buses, 2GB RAM (buffered), 2x WD Raptor 10.000 rpm in RAID-0 (harddisk)

7. Camera setup Video data + Control signals Synch pulse

8. Video processing Points are automatically detected, identified and tracked over time and accross different views.Points are automatically detected, identified and tracked over time and accross different views. Reflective markers are placed on the ski jumpers suit, helmet and skies.

9. Photogrammetry Matching corresponding feature points from two or more cameras allows us to calculate the exact position of that feature point in 3D.Matching corresponding feature points from two or more cameras allows us to calculate the exact position of that feature point in 3D. Assumes that one knows the position and viewing direction of each camera.Assumes that one knows the position and viewing direction of each camera.

10. Camera calibration Measure exact coordinates in the hill using differential GPS and land survey robot station. Place visible markers at those spots and estimate a geometry (relationship between 2D and 3D). Reconstruction is then trivial.

11. Visualization Feature points are connected back onto a 3D model of the ski jumper. Allowed to be moved and controlled in a large static model of the ski jump arena.

12. Granåsen ski jump arena

13. Conclusion A lot of challenging topics Remains to be seen how well the ski jumpers will perform based on this kind of feedback.

14. Are you ready to jump?