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  1. #26
    Join Date
    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_paradox
    Mo' skimo here: NE Rando Race Series

  2. #27
    Join Date
    Mar 2012
    Location
    The Bull City
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    14,003
    Quote 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
    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!

  3. #28
    Join Date
    Aug 2016
    Location
    关你屁事
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    9,533
    Sometimes trails get rerouted and signs aren't changed.

  4. #29
    Join Date
    Mar 2012
    Location
    The Bull City
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    14,003
    Quote Originally Posted by dunfree View Post
    Sometimes trails get rerouted and signs aren't changed.
    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!

  5. #30
    Join Date
    Feb 2008
    Location
    Donner Summit
    Posts
    1,251
    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.

  6. #31
    Join Date
    Mar 2012
    Location
    The Bull City
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    14,003
    Quote Originally Posted by teledad View Post
    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.
    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!

  7. #32
    Join Date
    Mar 2012
    Location
    The Bull City
    Posts
    14,003
    Quote 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
    Quote Originally Posted by SumJongGuy View Post
    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??
    I guess there is also an up and down factor not included when measuring distances looking straight down at a map.



    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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