1. Reliability of a Real Time Optical Navigation Feedback System for Training Alpine Skiers Richard Kirby, Advanced Racing Computers Troy Flanagan, Director of Sport Science, USSA Alan Schönberger, Ski Studio

2. www.advancedracingcomputers.com Introduction “When performance is measured performance improves and when performance is measured and reported the rate of performance improvement accelerates.” -- Thomas S. Monson New tool requires validation of reliability of data.

3. www.advancedracingcomputers.com PROBLEM: DETERMINE RELIABILITY OF VLINK DATA

4. www.advancedracingcomputers.com VLINK DEVICE

5. www.advancedracingcomputers.com HOW IT WORKS Click here to play video

6. www.advancedracingcomputers.com Y X

7. vLink vs. GPS Standard GPS samples at 1 Hz. At 20m/s that is a sample every 20 meters. dGPS samples at 20 Hz or once every meter. vLink samples at 6500 Hz or once every 3 mm.

8. www.advancedracingcomputers.com

9. 15.2 m/s 0.09° 16.0 m/s 0.52° 15.6 m/s 0.19° 16.3 m/s 0.21° 16.1 m/s 0.20° 16.0 m/s 0.07° 16.2 m/s 1.16° 15.5 m/s 1.12° 15.7 m/s 0.06° 16.0 m/s 0.03° 15.7 m/s 0.41° Inside ski came off edge too soon here… … causing Will to be thrown into air, becoming un-aerodynamic and loosing 0.6 m/s.

10. www.advancedracingcomputers.com HOW CONFIDENT ARE WE THAT 16.9 M/S IS FASTER THAN 16.7 M/S AS MEASURED BY THE VLINK? Tracking Skiers with the vLink

11. www.advancedracingcomputers.com Accuracy vs. Reliability Accurate and reliable Reliable, requires correction to be accurate Low reliability

12. www.advancedracingcomputers.com Tests Accuracy –CNC Mill Test Reliability –Sled Test on Snow –Carpet Test

13. www.advancedracingcomputers.com Mill Test CNC Mill Silica Paper to simulate snow surface Controlled Distance = 5 m N = 12 Mean = 5.00 meters SD = 8 mm Typical error = 0.22%

14. www.advancedracingcomputers.com SLED TEST EXPERIMENT SETUP On snow

15. www.advancedracingcomputers.com SLED TEST RELIABILITY RESULTS Typical error = 1.57% N = 35

16. www.advancedracingcomputers.com Sled Test Issues Soft snow conditions made repeatability difficult. Sled frame unstable as snow softened. Data showed non-random errors - distances decreased consistently test after test. Questioned accuracy setup vs. data accuracy.

17. www.advancedracingcomputers.com RELIABILITY STUDY 2

18. www.advancedracingcomputers.com RELIABILITY STUDY RESULTS Typical Error = 0.37% N=35

19. www.advancedracingcomputers.com CONCLUSIONS Due to the instability of the on-snow test fixture it is difficult to say what part of the error was the vLink and what part was the experimental setup. However, the measured typical on-snow error of 1.6% would suggest that one would typically be within 0.3m/s of the correct speed at GS speeds. However, the experimental setup needs to be improved for valid results. Carpet tests suggests that the resolution could be better than 0.1 m/s at a speeds of 20 m/s. Technology capable of 0.05 m/s resolution

20. Reliability of a Real Time Optical Navigation Feedback System for Training Alpine Skiers Richard Kirby, Advanced Racing Computers Troy Flanagan, Director of Sport Science, USSA Alan Schönberger, Ski Studio

21. www.advancedracingcomputers.com Support Slides

22. www.advancedracingcomputers.com Filtering Required on Snow

23. www.advancedracingcomputers.com Filtering method Holes or pockets in snow

24. www.advancedracingcomputers.com Filtering introduces error when between digital values Actual Speed Measured Speed Resolution