True Distance

[PapaGarrettP]

I have never seen this addressed. Maybe I am missing something.Are distances between points on the AT (on signs, in guide books) quoted in two dimensions or including differences in elevation?

In other words, say the trail distance between Point A and Point B measures out to 10 miles on a map, but there is a big mountain in between (necessitating more steps to cover the same horizontal distance). Would the trail sign and AT guide book list the distance as 10 miles or the actual footpath distance?

Anyone know?

Thanks,

PapaG

[Moose2001]

Mileage on the maps, trail signs and actual distance are all the same.

[BobTheBuilder]

It is a good question, because they are NOT all the same.

If you were climbing a constant inclined slope of 10 degrees in a straight line, the "map" view, or view straight down, would be different than the actual tape-measure distance you travelled. If the "map" view showed 1 mile, your actual tape distance would be 1 mile divided by the cosine of 10 degrees, or 1.015 miles, a full 81 feet further. Since the difference is based on slope, it doesn't matter if you are going up or down, so the difference is cumulative.

I don't know for sure how they measure trail distance on the AT, but I think the thing was originally measured by a wheel, which would give you the tape-measure distance. Not sure what they do now for relocations, though.

[tdoczi]

I don't know for sure how they measure trail distance on the AT, but I think the thing was originally measured by a wheel, which would give you the tape-measure distance. Not sure what they do now for relocations, though.

i dont see how they could do it any other way and hope to be anything even close to accurate, given not just elevation changes but curves and bends in the trail. really, pick 2 points, lets say from clarks valley to swatara gap. how would you measure the length of trail through there in any way that would even be remotely correct other than by measuring the actual trail, thereby including the elevation changes?

[theoilman]

I think I have read that the posted numbers are "linear" distance which I understand to mean it does NOT take into consideration elevation changes. I don't see how it would be possible to do a measuring wheel measurement of the AT.

[Bloomer]

I did a intership at the ATC Mid-Atlantic office 1997 while at Penn State and during that time I saw a 'distance' wheel. It wasn't like a wheel used by a utility company. The tire was inflatable like a bike. But did see one! At the Scott Farm if I remember correctly.

[PapaGarrettP]

So, who believes that the distance listed in the AT Guide "North Carolina-Georgia" on page 255 from Springer Mountain (0) to Davenport Gap (238.1) on page 250, is actually 238 hiking miles?

[tdoczi]

I think I have read that the posted numbers are "linear" distance which I understand to mean it does NOT take into consideration elevation changes. I don't see how it would be possible to do a measuring wheel measurement of the AT.

how would it be possible to measure as linear distance and include all the bends and turns in the trail?


a measuring wheel measurement is clearly possible. tedious and time consuming? sure. but since when does that equal impossible? in what way do you think it would actually BE impossible?

[tdoczi]

So, who believes that the distance listed in the AT Guide "North Carolina-Georgia" on page 255 from Springer Mountain (0) to Davenport Gap (238.1) on page 250, is actually 238 hiking miles?

i never believe any of the mileages in the whites while i'm hiking either, but that doesnt mean theyre wrong.

[Tinker]

I noticed that, on the AT maps, the contour line maps did not line up with the elevation maps. The mileage on both maps has been correct, in all of the series that I've used to date. The only exceptions are when the Trail is rerouted and the wooden signs (usually at trail junctions) are not updated.

[atmilkman]

According to AWOL Springer to Katahdin by way of a balloon would only be 1300 miles. Could this be considered linear?

[Moose2001]

In fact, the AT has been measured by a measuring wheel. I know Warren Doyle's groups have done it. I'm sure the maintaing clubs have measured their sections as well. That's how the mileage that's on the AT maps is found. I believe the AT has also been measured using GPS.

[Bearpaw]

When building new trail on the Cumberland Trail, we always measured distance with a wheel. I have no doubt it is done the same way with the AT. Of course, there have also been GPS surveys done for the whole AT corridor. And when folks did a GPS survey on parts of the CT I helped build, the results were surprisingly close to the wheeled distances we measured.

To answer the OP, yes, the mileage listed in the Data Book is actual hiking mileage, as it existed just before publication for the year. Relocations happen all the time, so you might have a little variation when you actually hike.

[Tinker]

According to AWOL Springer to Katahdin by way of a balloon would only be 1300 miles. Could this be considered linear?

Yes, or "as the crow flies". The maps of the AT show actual distance hiked, not a straight line without respect to elevation gain and loss.

[pyroman53]

Interesting question about mileage. I'd love to hear what they actually use for mileage in the books.

How could you correct for slope? I can think of two ways...

The old way: use the wheel and apply an average slope correction factor for each segement. Subtract (per previous reply). Not really that hard. Surveyors been doing this for centuries, or however long they've been surveying.

The new way: Use GPS. Collect a Track while walking the segment. Download into GIS software (Geographic Information System) and get the length of the track. Quick process for GIS geeks. In fact, I can't remember if the GPS might even give you the length of the track automatically. That would be actual horizontal distance (map distance) The better the GPS, the better the accuracy. Someone (Trail Name "BP") did this for the entire AT a few years back. That's the data Backpacker Magazine uses for their tracks and profiles found here:http://www.backpacker.com/global/47. I met him at Neel Gap on his 2 year SOBO.

[gpburdelljr]

Typically distances, a road for example, are given as horizontal differences without accounting for the fact that the sloping distances are longer. The following is from the ATC website "...Every December, the latest mileage and shelter information for the 11 official guides is updated from volunteers who are constantly improving the trail, with volunteer Daniel D. Chazin of Teaneck, N.J., pulling it all together since 1983.". I do not know, but I suspect that different volunteers measure in different ways. Probably some use GPC (which will give horizontal distance), and some a distance wheel (which would give slope distance). I ran a profile on the Appalachian Trail using DeLorme Topo, and the difference between horizontal difference and trail difference is only about 1%, so if the trail is about 2180 horizontal miles there would only be about 22 miles extra if you accounted for slope distance.

[yotarunner77]

What about mileage done not on the trail like to shelters and water sources? I know everyone goes a different rout but does anyone know the average mileage of the entire trip?

[4eyedbuzzard]

What about mileage done not on the trail like to shelters and water sources? I know everyone goes a different rout but does anyone know the average mileage of the entire trip?

Do you mean including walking to the privvy, walking around in towns, backtracking because you lost the trail, and all that stuff? I doubt anyone keeps track of it. Add maybe 100 miles and you're good.

[Jim Adams]

The mileages on the AT have all been measured with a wheel and also with GPS. I have seen Warren measuring with a wheel on my thru hikes, a party unknown to me measuring with a wheel and I do believe that DellDoc measured it with GPS (2002?). When You are out there the time and distance that a thru takes, you become very in-tune with time vs mileage. The only distance that seemed way off to me was from the road crossing after Moosilake to the next shelter at the base of South Kinsman...seemed way too far ( 2 miles? )in both distance and time walking...both thrus.

geek

[LIhikers]

........ I do believe that DellDoc measured it with GPS (2002?). .......
geek

I think he did it twice actually. My wife and I met him on the trail and he had a backpack full of GPS and recording equipment. He explained to us that he hiked the center of the trail as it appeared to him and the equipment recorded his position every few seconds. So I guess the wheel isn't the only kind of equipment used for measuring the trail.