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Thread: GPS experts/Dorks:
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04-30-2018, 12:15 PM #26Gel-powered Tech bindings
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- Dec 2004
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- Amherst, Mass.
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- 4,684
I suspect the various GPS devices are recording at a shorter interval than the old estimates for the NPS maps, as per this factor:
https://en.wikipedia.org/wiki/Coastline_paradoxMo' skimo here: NE Rando Race Series
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04-30-2018, 01:16 PM #27
This is my guess as well.. The NPS map probably measured some of the winding parts as straight in larger sections where our GPS devices showed the actual length winding back and forth.
I suppose that a true geek could take the GPS data and run some exponential smoothing to convert the really windy sections back to straight lines and arrive at something closer to what the NPS map shows eh??Go that way really REALLY fast. If something gets in your way, TURN!
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04-30-2018, 01:40 PM #28
Sometimes trails get rerouted and signs aren't changed.
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04-30-2018, 01:51 PM #29
So the blaze marks would be different from the park map in some spots? Might explain some of it but not 20%. FWIW we were teaching the younger scouts basic orienteering using just the topo map and compass.... but making sure to stay within site of blaze marks. The guy teaching them was super familiar with the trails over the past 10 years. Kids wandering around weren't carrying the GPS though, only adults sticking to the marked trail had the GPS running.
Go that way really REALLY fast. If something gets in your way, TURN!
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04-30-2018, 02:54 PM #30Registered User
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- Feb 2008
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- Donner Summit
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If the trail is either visible by satellite (not completely covered by trees) or marked on the USGS maps, you can upload the track to gpsvisualizer.com (or Caltopo, or even Strava) and see how far it wanders from the trail.
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04-30-2018, 03:27 PM #31
Might try to do that next time. I did see that the device I have can export the track if it's saved properly. I was just using the metrics trip odometer to get the distance. Probably still had the device on for the 90 mile drive home though so too late to save the track hahahahaha..
Go that way really REALLY fast. If something gets in your way, TURN!
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04-30-2018, 03:43 PM #32Quote Originally Posted by Jonathan S. View Post
I suspect the various GPS devices are recording at a shorter interval than the old estimates for the NPS maps, as per this factor:
https://en.wikipedia.org/wiki/Coastline_paradox
Looking down only gets the base of A to B called "d". You can calculate the hypotenuse via Pythagorean with the height, but the true line will be even a little longer than that.Go that way really REALLY fast. If something gets in your way, TURN!
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