I posted this in another thread but thought I’d try and get a few more answers.
Just wondering…the sprint the other day that was decided by .0002 seconds as registered by this transponder. If one transponder is mounted closer to the front wheel then the other, even if by only 2mm…then this would have made a difference in the times registered and could account for an error in the .0002 winning margin. Yes…no…? And if they are all mounted in the same spot…how do they account for the longer wheel bases of larger bikes. I hope they are all mounted by measuring from the front of the front wheel…and VERY accurately too!! I assume the time is registered as the transponder crosses a particular spot in the road…similar to Champion Chips.
I just replied to your same post on the other thread…but here it is for this one:
We use the same looking transponders for our road races here in Cincy. The race organizers measure from the front wheel to the transponder to be sure everyone’s is in the same place. I’m guessing if it is fairly accurate for local level stuff…le Tour is very precise!
Are you sure? because I can see who won from this, I’m sure the commissaires didn’t have a problem either. Also I’m not sure the precision of the transponder is down to 10^-4 of a second.
I am not so sure you can actually see who won from this picture. Sure, the Rabobank rider’s front wheel looks closer to the line, but he is also further away so it could be an illusion.
This is a very odd looking photo anyway. Notice the heavily curved spokes.
Foto-finish is design and installed in order to take all those things into consideration!
Have you ever think about this in the track running races?
I guess we should be worried if the right runner has been awarded the prize, after all most of the 100m races results are decided after checking the foto-finish!!!
This is a very odd looking photo anyway. Notice the heavily curved spokes.
The finish line camera has a vertical slit aperture, and the film moves rapidly past the aperture. Things that are moving (like legs of a sprinter or spokes of a wheel) will have different orientations as they pass the aperture. The rim end of a spoke that is pointing directly forward will pass first. Each successive bit of the spoke going toward the hub will be a bit lower (as the wheel rotates) as it passes the aperture, with the bit being less as it gets closer to the hub (angular velocity being conserved). Thus, the line of points of the spoke as they pass the aperture will appear curved for this spoke. A spoke nearly vertical will pass the aperture very quickly, and show little (or no) distortion. Look at the picture, think about the orientation of the various distorted bits as they pass the aperture, and you’ll understand. Or not.
Very good explanation. Now it makes perfect sense. I was thinking in terms of a shutter and I couldn’t see how the accuracy of the photo would be so much greater than the shutter speed.
I am not so sure you can actually see who won from this picture. Sure, the Rabobank rider’s front wheel looks closer to the line, but he is also further away so it could be an illusion.
You are right because I do not think we can judge simply from the single frame out of a series of images. The commisaires were able to base their descission on a series of images that probably indicated which racer sustained the most momentum accross several frames of the series which was not offered to the OLN viewers (not sure about European views). I feel confident that if the full phot series had been presented, we would have seen how the winner overtook the other and continued to maintain momentum before and after crossing the line while the other racer was overtaken at the line because he was no longer sustaining the effort and had begun decelerating as they crossed the line.
I am not so sure you can actually see who won from this picture. Sure, the Rabobank rider’s front wheel looks closer to the line, but he is also further away so it could be an illusion.
You are right because I do not think we can judge simply from the single frame out of a series of images. The commisaires were able to base their descission on a series of images that probably indicated which racer sustained the most momentum accross several frames of the series which was not offered to the OLN viewers (not sure about European views). I feel confident that if the full phot series had been presented, we would have seen how the winner overtook the other and continued to maintain momentum before and after crossing the line while the other racer was overtaken at the line because he was no longer sustaining the effort and had begun decelerating as they crossed the line.
I think you are mistaken. I believe there is only one image. Read Ken’s explanation above.
I think you are mistaken. I believe there is only one image. Read Ken’s explanation above.
Yes, that could be but there have been several times over the last year where media coverage included more than one image of the same racers involved in a ‘photo’ finish. I have also seen first hand officials reviewing the output from the finish cam at various races (USCF and UCI) and in all cases the output was multiple images from a brief interval triggered when the racer entered the target zone.
Below are the specs for the transponders and base station of the timing system. I am not sure what the ‘Timing Resolution’ actually refers to, but they claim .0085 for the transponder and .001 for the base station. Of course, the whole system is built around an antenna on the ground inducing and receiving a signal from the transponder. Accuracy would also be affected by the layout of the actual wire, how straight is it?
Specifications:
AMB Activ Timing Chip
Number of chips: unlimited
Timing resolution: 0.0085 sec.
Dimensions: 43.7 x 27.3 x 11.3 mm
Weight of chip: 16 grams
Chip position : max. height 3 ft (90 cm)
Max. speed: 45 mph (75 km/h)
Temperature range: -4 to 122 °F (-20 to 50 °C)
Battery life: 100,000 passings
Signal transfer: magnetic induction
Specifications:
AMB Activ Decoder
Dimensions: 120 x 170 x 55 mm (4.7 x 6.7 x 2.2 in)
Timer stability: 0.5 ppm
Timing resolution: 0.001 sec
Temperature range: 0 to 50 °C (32-122 °F)
Humidity range: 10% - 90% relative
Power supply: 12 VDC input
Flash Memory: 65,000 passings
Output: RS232 and 10-base T (TCP/IP) Ethernet
I think you are mistaken. I believe there is only one image. Read Ken’s explanation above.
Yes, that could be but there have been several times over the last year where media coverage included more than one image of the same racers involved in a ‘photo’ finish. I have also seen first hand officials reviewing the output from the finish cam at various races (USCF and UCI) and in all cases the output was multiple images from a brief interval triggered when the racer entered the target zone.
Video replay is not the same as the photo finish technology used here. There is no guessing or doubt with a photo finish which is only looking at the finish line, not a zone.
