While modern measurement devices are wonderful to help us estimate our training runs and bike rides, they aren't always accurate.
A GPS unit is not accurate enough for a course to be USATF-certified. Even the best commercially-available GPS unit is only accurate to about 12 feet at any given time, and can be hundreds of feet off in accuracy. Most units will show you what their current accuracy is, and you can watch it vary from 12 feet to 350 feet or more. GPS units must have a clear view of at least three satellites to get a reading, and the more they can acquire, the more accurate they are. However, trees, buildings, and even your body can interrupt the signal, making it less accurate at any time.
Further, they only check their position periodically, not constantly. Some units check every second, some every 20 seconds. The user can sometimes set the unit to check at certain time or distance intervals, but if the unit has lost contact with the satellites, it can't tell where it is, so it misses that checkpoint. So, if you are running quickly, you may make a few turns while the unit doesn't have contact, so that section will be measured incorrectly.
This is a very nice web site.
Well done Duane.
I want GPS tracks of races.
For anyone out there who has access to pre-race contacts for runners, I am extending an invitation to you to invite your runners who wear a GPS to send an email to firstname.lastname@example.org, containing their track, the race name, and their finishing time (I may compare the time in the GPS file to their clock time). They can share anything else with me they like.
But, I want to compare as many tracks from the same race on the same day, as possible.
If you do extend the invitation for one of your up-coming races, please let me know, so I can do my homework before tracks start coming in.
Thanks to all who assist in this. I will share the results.
Duane, I'll see if I can get something posted on the RW/RT Boston microsite. Would 20,000+ runners be a good sample size?
Holy Schamoly! 20,000 people aren't motivated enough to send the files (I hope!). But, it would be a good sample to show how much agreement there would be. As long a runners whose tracks said the course was short also sent in their files.
Thanks! That should help a lot!
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