Saturday, I ran the Harpoon 5-miler here in Boston. Thanks to a new technology, this was the simplest and easiest race ever for tracking my time. The race bibs had ChronoTrack B-Tag strips–completely eliminating the hassle of a timing chip. I did OK:
Nettime Pace Name Race# City/state ======= ===== ====================== ===== ======================= 40:19 8:04 David Atkins 2566 Westwood MA
For those unfamiliar with road races, the technology has evolved dramatically in the past few years. When there are 3000 people in the race, it can take a person standing at the back with the walkers and strollers, 3 minutes or more to cross the starting line. You cannot count on the actual (guntime) timing from when then starter’s pistol goes off to when you cross the finish line to know your true time and pace. So most races now measure “nettime” the difference between when you cross the starting line and when you cross the finish line. But how is this done?
Until a few years ago, it wasn’t. Runners came to the finish line, tore off a tag from their race bibs and handed it to a volunteer. Other volunteers stood by with stopwatches and called out the times. Someone wrote all that down. That is still how its done when a race cannot afford the more sophisticated electronic tracking systems.
Until this year, those systems consisted of a timing chip you tied to your shoelaces. At the end of the race, you would bend over and remove the chip (don’t pass out!) and put it in a bucket to be collected by the race organizers. Fail to return the chip–pay a fee. Last year, that system was replaced by a disposable tag you threaded through your shoelaces. But, even with a video and instructions, those tags were hard to figure out.
This year, the tag was embedded in the race bib itself. No confusion. No delay. Just pin the bib to your shirt and run. A few minutes after crossing the finish line, you go to a results wall where the real-time numbers are being posted.
The technology behind the bib is called Radio Frequency Identification (RFID). The start/finish line is covered by mats containing radio transmitters that emit an electric field and induce a small current in the tag you are wearing which then broadcasts back your ID code. It is the same idea behind Fast Lane transponders and keyless entry systems. The transmitter/receiver creates an electromagnetic field around a highly localized area. The materials in the tag act as an antenna to collect the energy from that field and reflect back a unique electronic signature which is then detected and recorded along with the timestamp.
The link to RFID above provides a full, technical description of the electronics involved, but the advance for the purpose of racing timing appears to be in reducing the weight of the transponder so significantly that it can be unobtrusively added to the back of a race bib. There are just two plastic strips on the bib–antenna material far enough apart to be able to pick up the very high frequency signal from the mat and yet still resonate back an accurate and unique signal.
For those who can remember televisions with “rabbit ears” for antennas, you may also recall how frustrating it was to adjust the antenna, then step away and lose the reception. Perhaps someone was appointed to hold the antenna or stand nearby during critical moments of football games, etc. The principle is similar–a high frequency electromagnetic field is influenced by other conductive materials which generate interference by “reflecting back” some of the energy. Sometimes this enhances the signal; other times, it gets in the way. But the challenge for RFID is to do this in a reliable, predictable manner so that 100% of the time, the system will activate your race bib and then get the right number back–all done simultaneously with dozens of other runners who might be crossing the same field at the same time.
ChronoTrack seems to have nailed it with these race bibs.
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