How was the mileage in the White Mountain Guide originally determined

[Ed'n Lauky]

In a discussion of Odometer accuracy on a GPS website, I was asked how the mileage in the White Mountain Guide was originally determined. Behind the question is another question: How accurate is the mileage as given in the White Mountain Guide. Anyone know?

 

[TEO]

I'm pretty sure that the traditional way to measure trail distances is with a wheel.

 

[Still Steppin']

Found this quote by Jon Burroughs in a red lining article at http://www.outdoors.org/publications/outdoors/2012/features/red-line-the-white-mountain-guide.cfm.

“I became the first individual to personally log every maintained trail in New Hampshire by surveyor's wheel and to keep detailed notes of every trail,” Jon says. “This led to a significant overhaul of the 25th edition of the guide on many levels,” including hundreds of modifications and new maps based on his mileage wheeled.

Would seem to verify the wheel method. BUT, I'm sure I've been on a few trails where the wheel skipped a few turns!

 

[DougPaul]

In a discussion of Odometer accuracy on a GPS website, I was asked how the mileage in the White Mountain Guide was originally determined. Behind the question is another question: How accurate is the mileage as given in the White Mountain Guide. Anyone know?

We've had the same discussion here a number of times...
http://www.vftt.org/forums/showthread.php?44078-Book-Milage-vs-GPS-Milage-Which-to-believe
http://www.vftt.org/forums/showthre...f-trail-distances-on-signs-and-in-guide-books
http://www.vftt.org/forums/showthread.php?41047-Yet-another-Garmin-GPS-question

There is no way of determining the accuracy (to a high degree of accuracy...). The length of a trail is a fractal (ie the length is a function of the size of your ruler) and has no single unique "correct" length. Since you cannot know the exact correct length, you cannot determine the accuracy of a measurement.

Consumer GPSes generally compute the location once per second and the recorded tracks save a subset of these locations. The simplest way to compute the length is to sum the distances between adjacent points however the sparser tracks will tend to give shorter distances. (The odometer presumably is computed from the one per second locations.)

The consumer GPS locations also have errors which will tend to increase the computed distance. And to complicate matters, there is cross-point smoothing in the GPS so the points are not independent...

Doug

 

[Mohamed Ellozy]

There is no way of determining the accuracy (to a high degree of accuracy...). The length of a trail is a fractal (ie the length is a function of the size of your ruler) and has no single unique "correct" length. Since you cannot know the exact correct length, you cannot determine the accuracy of a measurement.

Best simple explanation is in the Wikipedia article Coastline Paradox:

The coastline paradox is the counterintuitive observation that the coastline of a landmass does not have a well-defined length. This results from the fractal-like properties of coastlines.

More concretely, the length of the coastline depends on the method used to measure it. Since a landmass has features at all scales, from hundreds of kilometers in size to tiny fractions of a millimeter and below, there is no obvious limit to the size of the smallest feature that should not be measured around, and hence no single well-defined perimeter to the landmass.

That article has a neat figure that shows the different coastlines using 100 km and 50 km "rulers".

 

[RoySwkr]

Found this quote by Jon Burroughs in a red lining article at http://www.outdoors.org/publications/outdoors/2012/features/red-line-the-white-mountain-guide.cfm.

“I became the first individual to personally log every maintained trail in New Hampshire by surveyor's wheel and to keep detailed notes of every trail,” Jon says. “This led to a significant overhaul of the 25th edition of the guide on many levels,” including hundreds of modifications and new maps based on his mileage wheeled.

There is no doubt that JB's work was a significant improvement to the WMG, although I'm still miffed that he was allowed to introduce at least one error even after I objected. And his claim to measure every maintained trail in NH is spurious, he tried to keep many trails on private (including quasi-public) land out of the southern book in particular.

Prior to the edition he served as associate editor, the guidebook mileages varied from carefully measured to pure conjecture - and at least one trail may have been carefully measured in km but the Joy St staff used a 1:1 ratio to convert it to miles. I know that some trails have had significant relocations but many have not - it would be interesting for somebody to build a spreadsheet of how each trail mileage has changed by edition.

 

[TJsName]

I've wondered if people could upload the GPS tracks to come up with crowd sourced distances. This is similar to my dream of car GPSs predicting traffic.

 

[peakbagger]

Some folks are still thrown off by mileage measured by map compared to actual trail miles. I don't think I could locate my opisometer if I tried but its always interesting to see folks take pains measuring items exact as possible on a two dimensional map and then wonder why the distance they hiked doesn't match the guide. Unless everyone agreed to a very tight and standard refresh rate on their GPS's I expect the noise from varying sampling intervals would screw up the the value of crowd sourcing.

I used to survey in college and on occasion we would run into a "farmers survey" laid out on sloping terrain where it was obvious that the distances were paced out along the slope. Some folks would be quite surprised that the deed description would vary widely from the new survey as deed are stated as distances perpendicular to the plane of the earth. If there were "monuments" (pipe, blazed tree, granite post or barbed wire intersection) at the corners, they wouldn't lose any land but if there wasn't anything in the field their back property line might move forward quite a distance on a hill.

 

[DougPaul]

I've wondered if people could upload the GPS tracks to come up with crowd sourced distances.

Crowd sourcing is not a panacea and can create more problems than it fixes. Different people will use different GPSes with different settings. Some people will also carry their GPSes in poor locations (eg on their belts). You would get far better results with someone with professional training using a survey grade GPS with a choke-ring external (ie professional-grade) antenna.

The WMFS published GPS tracks for most of the trails in the WMNF. They have been converted into GPX files and been made available on a website. See http://www.vftt.org/forums/showthread.php?t=38643 for more info. You could compute an estimate of trail distances from these tracks pretty easily.

This is similar to my dream of car GPSs predicting traffic.

"Predictions are hard, especially about the future". (Niels Bohr)

Try magic.

Doug

 

[Tom Rankin]

I'm still convinced the mileages on signs are put there to teach you not to trust them!

 

[RoySwkr]

I'm still convinced the mileages on signs are put there to teach you not to trust them!

Many of the FS signs are manufactured in Federal prisons (look for FCI on the back), the makers may not know or care about hiking even if they don't deliberately introduce errors for fun

And then there are those who can't read guidebooks including some AMC staff. Last time I was at Mizpah Hut there were some nice laminated pages (presumably done off-site) giving hiking distances and times to various points from the hut - but on close inspection they actually used the guidebook time _to_ the hut from those points. When I pointed this out to a crew member they said it was a good idea to give a longer time than the correct one - sure that works for the time to Rte.302 but the time they give to other points was too short.

 

[TrailwrightBratt]

Gene Daniel and I have measured many trails over the years with a wheel as have many others.
Errors can be kept to a minimum by the skill of the user. There are tricks of the trade so to speak and control of the wheel is most important with no swerving from side to side.
I have measured all the trails on Belknap several times. I have had good luck and on several occasions I would measure up then down and reading within 10 feet at the half way point.
Some errors are because of rounding off.
A GPS does not measure the real on the ground length or grade but in general plenty close enough.
Careless wheel rolling such as over boulders etc. can cause errors but again plenty close enough.
Of course there is always the question of how accurate does a measurment have to be. 100 ft. a tenth of a mile (528 ft.)??

 

[Kevin Rooney]

Steve Smith has told me on more than one occasion that when he measures a trail's distance, he uses a steel tape. Am quite sure he said his wife helps him as with this task.

 

[Remix]

As an aside, the whole fractal thing and the issue of accuracy came about when neighboring countries posted wildly different lengths for their shared mutual border length.