View Full Version : Mile Measurements on the AT

KilroyWasHere

04-03-2018, 09:26

Hi Everybody,

Just curious, are miles on the AT measured by a measuring wheel these days or by GPS? More specifically, is all the walking on switchbacks part of that measurement or are switchbacks measured as the crow flies?

Thanks in advance

Gambit McCrae

04-03-2018, 09:37

The trail is measured as the trail wonders, not as a crow flies. I am almost sure that it has or is measured by wheel and GPS as well, depending on who is doing the measuring. I would say that it is one of the most accurate trail mileages out there. I know that when I carried GPS on parts of the BMT that my results were was off from the data books...Like, miles off along the lakeshore trail

It's the wheel. I have encountered them several times. I do think that they cheat in the AMC. Those quarter of a mile signs around all the huts are more like a half mile.

I would say that it is one of the most accurate trail mileages out there.

the GSMNP redid their measurements years ago and its quite fascinating how the guy measured them all...

link below....

http://www.smhclub.org/Stories/Lochbaum.htm

Odd Man Out

04-03-2018, 11:53

I've seen this discussed before. I'm not sure what the OP was meaning by "as the crow flies" since with high enough resolution, a GPS track can measure every twist and turn of the trail as one would with a wheel. However the other thing that people have asked is does a GPS track take into account the additional mileage due to elevation gain and lost. The answer is that it doesn't really matter as much as most people think. You can estimate the difference with geometry. Compare two hikers. One hikes 10 miles a path that is perfectly flat (horizontal) straight line. The other hiker also hikes to a point that is 10 miles away (on a horizontal line). He also hikes a perfectly straight line, but follows the contours of hills up and down which adds some extra distance. If we assume the incline up and down is always on a 10% grade (I use 10% because I recall reading somewhere that the AT averages 10% grade over the length of the trail, but that could be wrong. I think MapMan measured it once), you can use geometry to calculate that the first hiker hikes exactly 10 miles and the second hiker hikes 10 miles plus 263 feet, which over 10 miles isn't much. Over a 2000 mile trail, the difference is only about 10 miles. From the point of view of a cartographer, it is in interesting questions. From the practical point of view for the hiker, the difference isn't particularly relevant, unless you are taking a bee-line hike from the summit of El Capitan to the bottom of Yosemite Valley.

the GSMNP redid their measurements years ago and its quite fascinating how the guy measured them all...

link below....

http://www.smhclub.org/Stories/Lochbaum.htm

I very thankful there are people as dedicated as this guy in the hiking community.

AllDownhillFromHere

04-03-2018, 13:53

Avery supposedly wheel-measured the whole thing back in the day.

Avery supposedly wheel-measured the whole thing back in the day.

yeah....i believe he did...

but, the trail has changed an awful lot since then...

Sarcasm the elf

04-03-2018, 15:01

Avery supposedly wheel-measured the whole thing back in the day.

yeah....i believe he did...

but, the trail has changed an awful lot since then...

If I recall, there is a story that the original trail (since rerouted) carved a particularly grueling path up a steep mountain in the South the name of which escapes me. The route as supposedly flagged as a joke by the trail builders because they wanted to see of Avery and his wheel could make their way up the darn thing.

Hi Everybody,

Just curious, are miles on the AT measured by a measuring wheel these days or by GPS? More specifically, is all the walking on switchbacks part of that measurement or are switchbacks measured as the crow flies?

Thanks in advance

Around 2000, +- a year I met a group of four hiking up Stratton Mountain on the AT in Vermont. I remember one of their names. It was Dr, Dell. One of the hikers was carrying a large devise on his back that was what I would think was some kind of GPS unit. They told me that they were doing a satellite map of the trail. They had a support vehicle that would meet them at road crossings. They would than relay the info that they collected, by downloading it by phone. They were doing this to establish accurate measurement of the trail.

They were doing this before todays small GPS units and cell phones were in common use.

Some years later I saw an article about the project and that Dr. Dell had passed away.

AllDownhillFromHere

04-03-2018, 15:54

Around 2000, +- a year I met a group of four hiking up Stratton Mountain on the AT in Vermont. I remember one of their names. It was Dr, Dell. One of the hikers was carrying a large devise on his back that was what I would think was some kind of GPS unit. They told me that they were doing a satellite map of the trail. They had a support vehicle that would meet them at road crossings. They would than relay the info that they collected, by downloading it by phone. They were doing this to establish accurate measurement of the trail.

They were doing this before todays small GPS units and cell phones were in common use.

Some years later I saw an article about the project and that Dr. Dell had passed away.

That was Deldoc! I met him in 1999, somewhere in the mid-Atlantic. Backpack mounted GPS unit.

gpburdelljr

04-03-2018, 16:09

Since GPS data is now available for the entire trail, I would assume that current trail measurements are based on GPS. GPS measures horizontal distance, not slope distance.

AllDownhillFromHere

04-03-2018, 16:54

Deldoc info:

http://www.xyht.com/spatial-itgis/mapping-the-appalachian-trail-part-2/

Odd Man Out

04-04-2018, 08:42

Avery supposedly wheel-measured the whole thing back in the day.

There's a photo of him with his measuring wheel in the Appalachian Trail book.

There’s a sign at each end. Does it really matter how far apart those two signs are?

Wayne

There’s a sign at each end. Does it really matter how far apart those two signs are?

Wayne

when discussing the theoretical difference due to elevation change not being incorporated, no.

if, as the OP was asking, the measurements excluded accurately measuring the switchbacks.... well yeah, a 2200 mile trail that was actually 2600 miles might be an issue.

when discussing the theoretical difference due to elevation change not being incorporated, no.

if, as the OP was asking, the measurements excluded accurately measuring the switchbacks.... well yeah, a 2200 mile trail that was actually 2600 miles might be an issue.

The AT has been around long enough to have a decent idea of the gap between the two end points.

Asking if switchbacks are included in the total distance is.......

Y'all have fun.

Wayne

Asking if switchbacks are included in the total distance is.......

on one hand i agree totally. on the other, as dumb as it is, it does seem like some maps of some trails are measured in ways that dont include the walking length of the switchbacks in the total mileage.

or maybe people who insinuate such things arent correct. i dont know. but at a minimum there is chatter to that effect.

Pondjumpr

04-04-2018, 16:14

To answer the question more specifically, than it has already been answered.... As the crow flies, it is right at 1,117 miles, or just over half of the actual mileage taking into account for the "switchbacks." Credit Google maps for the measurement.

Odd Man Out

04-04-2018, 17:50

To answer the question more specifically, than it has already been answered.... As the crow flies, it is right at 1,117 miles, or just over half of the actual mileage taking into account for the "switchbacks." Credit Google maps for the measurement.

Yes it all depends on the resolution of the measurements. The coastline paradox states that if you make enough measurements, the distance of a highly convoluted path can approach infinity. No wonder hiking the AT is so hard. https://en.wikipedia.org/wiki/Coastline_paradox

johnacraft

04-05-2018, 14:55

are miles on the AT measured by a measuring wheel these days or by GPS? More specifically, is all the walking on switchbacks part of that measurement or are switchbacks measured as the crow flies?

Without knowing which specific trail or dataset you're referring to, I don't think anyone can answer your first question. But I can talk a little bit about how, for example, your phone app tracks your hike, which is similar to how a trail would be mapped via GPS (spoiler alert: whether wheel or GPS, "as the crow flies" from end to end has never been how it's done).

Your phone app starts by getting a GPS fix (http://www.satsig.net/maps/finding-lat-long-with-gps.htm), the more accurate the better (https://learn.sparkfun.com/tutorials/gps-basics). From GPS observations, the device makes an initial series of calculations to determine your latitude, longitude, and elevation, and the accuracy of those calculations.

Here are some sample data from around Max Patch:

42432

In that data you'll see a timestamp, the primary calculations based on GPS observation (grey), and also secondary calculations (green) based on the primary calculation results.

There is no bearing or speed calculation in the first row, because the secondary calculations in green are based on comparing two adjacent rows of data. If I hike for two hours, and store a trackpoint e.g. every 5 seconds, I will record 1440 trackpoints, and can calculate 1439 sets of values between adjacent points (point1 -> point2, point2 -> point3, point3 -> point4 . . . . point1439 -> point1440).

The Haversine formula (https://en.wikipedia.org/wiki/Haversine_formula) can be used to solve for horizontal distance between two trackpoints. Vertical distance is the difference between two <ele> values. The hypotenuse of the resulting right triangle is the distance hiked. (Add up the values of those 1439 hypotenuses, and you have total distance hiked.) Grade, speed, and compass bearing between each pair of points can be calculated as well.

If you have concerns about the accuracy of the initial observations (for example, if your device is in the forest, inside your pack brain), the same calculations can be performed between non-adjacent points (point1 -> point3, point1 -> point4, etc.) can be performed to check and smooth the resulting plot. (I can't really hike at 15mph.)

42434

The screenshots below show three different datasets plotted. The white dashed line is Google's plot of the AT (which, as you can see, is not always accurate). The red line is the ca. 2008 dataset from TNLandforms. The blue line is what my phone recorded on a hike in 2016.

42431

42433

The Haversine formula (https://en.wikipedia.org/wiki/Haversine_formula) can be used to solve for horizontal distance between two trackpoints. Vertical distance is the difference between two <ele> values. The hypotenuse of the resulting right triangle is the distance hiked. (Add up the values of those 1439 hypotenuses, and you have total distance hiked.) Grade, speed, and compass bearing between each pair of points can be calculated

Question:

Do you have any estimate of additional walking distance added to the AT due to elevation changes?

While my heart tells me it could be more than a few miles, my head tells me the distance added would be very, very small indeed.

Thoughts?

Question:

Do you have any estimate of additional walking distance added to the AT due to elevation changes?

While my heart tells me it could be more than a few miles, my head tells me the distance added would be very, very small indeed.

Thoughts?

It's about 8.75 miles. The average grade on the AT, whether going up or down is 9%. You get that number by dividing the total number of feet in ups and downs (around 515,000 feet of ups and around that many downs as well, depending on which end you start and end at) by the distance of the trail (around 2191 miles these days x 5280 feet per mile). That's around 1,030,000 feet divided by 11,568,480 feet, and that is a grade of 8.9%. Let's round that to 9%. Nine squared is 81. One hundred squared is 10,000. Add those. You get 10,081. Take the square root of that. You get 100.4 (with rounding). That means you hike an extra four tenths of a mile for every 100 miles you hike. Multiply that four tenths by 21.91 (the number of 100 mile legs in the 2191 mile trail) and you get about 8.75 miles of added distance.

Question:

Do you have any estimate of additional walking distance added to the AT due to elevation changes?

While my heart tells me it could be more than a few miles, my head tells me the distance added would be very, very small indeed.

Thoughts?

the reason a lot of us feel that way is because we're used to looking at elevation profiles with vertical exaggeration. if we draw an elevation profile of the entire trail, even if drawn fairly large (lets say 10 feet long) without vertical exaggeration you'd be looking at a flat line with a couple small bumps in the whites and a couple small bumps in the smokies. no matter how steep a hill feels over any actual practical gradient the additional horizontal distance added is almost nothing.

Hiking that far may cause my feet to hurt but all that math is causing my head to hurt.

It's about 8.75 miles. The average grade on the AT, whether going up or down is 9%. You get that number by dividing the total number of feet in ups and downs (around 515,000 feet of ups and around that many downs as well, depending on which end you start and end at) by the distance of the trail (around 2191 miles these days x 5280 feet per mile). That's around 1,030,000 feet divided by 11,568,480 feet, and that is a grade of 8.9%. Let's round that to 9%. Nine squared is 81. One hundred squared is 10,000. Add those. You get 10,081. Take the square root of that. You get 100.4 (with rounding). That means you hike an extra four tenths of a mile for every 100 miles you hike. Multiply that four tenths by 21.91 (the number of 100 mile legs in the 2191 mile trail) and you get about 8.75 miles of added distance.

That was a good explanation.

johnacraft

04-06-2018, 08:52

Do you have any estimate of additional walking distance added to the AT due to elevation changes?

If you measure the length of a trail by using a wheel, or by the method outlined in my post, then the answer is that elevation changes are already factored into the length, and there are zero additional miles to consider.

If you want to separate the horizontal miles from the vertical miles, that's a bit more difficult to tease out. If you give credence to the "equivalent to climbing Mt. Everest 16 times" claim, that's about 80 miles of vertical. That also implies about 80 miles of downhill hiking as well. But as map man's post show, taking square roots of squares complicates simple estimates of horizontal distance and vertical distance.

Highland Goat

04-06-2018, 09:05

If I recall, there is a story that the original trail (since rerouted) carved a particularly grueling path up a steep mountain in the South the name of which escapes me. The route as supposedly flagged as a joke by the trail builders because they wanted to see of Avery and his wheel could make their way up the darn thing.

You may be thinking of the Pinnacles of Dan.

mrcoffeect

04-07-2018, 07:43

If I recall, there is a story that the original trail (since rerouted) carved a particularly grueling path up a steep mountain in the South the name of which escapes me. The route as supposedly flagged as a joke by the trail builders because they wanted to see of Avery and his wheel could make their way up the darn thing.

That was the "peaks of otter".

That was the "peaks of otter".

So the trail did once go through there? Hiking in that area recently I found myself wondering that. Was a relo done because of the parkway?

peakbagger

04-08-2018, 12:25

Avery got plenty of practice in Maine, Despite the major relocations, the trail mileage is still just an approximation. As an example the Hunt Trail going up Katahdin has section where a hiker is petty well jumping from boulder and up and over house sized boulders. No really good way to wheel it. A GPS is going to be off as its not going to get the frequent climbs over boulders.

Highland Goat

04-08-2018, 18:26

So the trail did once go through there? Hiking in that area recently I found myself wondering that. Was a relo done because of the parkway?

If I recall correctly, the AT did not go over any of the three Peaks of Otter (Flat Top, Sharp Top, and Harkening Hill). The current trail is a few miles to the west, but an earlier route went much closer to Flat Top and Sharp Top – to the point where these were oft-taken side trails. I don’t know if the trail was rerouted specifically because of the Blue Ridge Parkway, but the federal government, as a side effect of the Parkway construction, built most of the trail in this area. The land was part of Natural Bridge National Forest when the Appalachian Trail was first built in the Peaks of Otter vicinity. Much of the trail in Natural Bridge National Forest was routed over forest roads, so the trail may also have moved away from the Peaks of Otter as part of efforts to put the AT on its own footbed.

There is an old story that the particularly vigorous route of the AT over the Pinnacles of Dan was a result of some early trail builders deliberately flagging a steep route and then sending Avery over it. The story claims that Avery liked the view, so the prank became the official route. I refer you to Walking With Spring or The Trail of My Life for the full version. I doubt this is true as the trail to the peak was originally a side trail, and then became the route of the AT as a result of dam construction on the Dan River.

Slo-go'en

04-08-2018, 23:05

The Long Trail is 268 miles from border to border. Interstate I91 does the same thing in 177 miles and is not exactly a straight line either. So, between wandering around and going up and down, the trail gained an extra 90 miles. That's a lot of extra miles!

SkeeterPee

04-08-2018, 23:52

when I took up backpacking one of my neighbors mentioned her dad did the first GPS track of the AT. Turns out he was DELDOC mention above. He did all of this after retiring.

If I recall correctly, the AT did not go over any of the three Peaks of Otter (Flat Top, Sharp Top, and Harkening Hill). The current trail is a few miles to the west, but an earlier route went much closer to Flat Top and Sharp Top – to the point where these were oft-taken side trails. I don’t know if the trail was rerouted specifically because of the Blue Ridge Parkway, but the federal government, as a side effect of the Parkway construction, built most of the trail in this area. The land was part of Natural Bridge National Forest when the Appalachian Trail was first built in the Peaks of Otter vicinity. Much of the trail in Natural Bridge National Forest was routed over forest roads, so the trail may also have moved away from the Peaks of Otter as part of efforts to put the AT on its own footbed.

There is an old story that the particularly vigorous route of the AT over the Pinnacles of Dan was a result of some early trail builders deliberately flagging a steep route and then sending Avery over it. The story claims that Avery liked the view, so the prank became the official route. I refer you to Walking With Spring or The Trail of My Life for the full version. I doubt this is true as the trail to the peak was originally a side trail, and then became the route of the AT as a result of dam construction on the Dan River.

interesting, thanks. the choice of trail routing and why often ends up fascinating me.

It's about 8.75 miles. The average grade on the AT, whether going up or down is 9%. You get that number by dividing the total number of feet in ups and downs (around 515,000 feet of ups and around that many downs as well, depending on which end you start and end at) by the distance of the trail (around 2191 miles these days x 5280 feet per mile). That's around 1,030,000 feet divided by 11,568,480 feet, and that is a grade of 8.9%. Let's round that to 9%. Nine squared is 81. One hundred squared is 10,000. Add those. You get 10,081. Take the square root of that. You get 100.4 (with rounding). That means you hike an extra four tenths of a mile for every 100 miles you hike. Multiply that four tenths by 21.91 (the number of 100 mile legs in the 2191 mile trail) and you get about 8.75 miles of added distance.

the miles added by elevation change is insignificant vs the effort added

I have said before, measuring the trail by units of effort with multipliers for weather etc would be a great tool for nerdy overplanners

jersey joe

04-10-2018, 08:43

That was Deldoc! I met him in 1999, somewhere in the mid-Atlantic. Backpack mounted GPS unit.

I met Deldoc on my 2002 thru hike leaving Boiling Springs. He was wearing that giant GPS backpack. That seemed like amazing technology back then.

It's about 8.75 miles. The average grade on the AT, whether going up or down is 9%. You get that number by dividing the total number of feet in ups and downs (around 515,000 feet of ups and around that many downs as well, depending on which end you start and end at) by the distance of the trail (around 2191 miles these days x 5280 feet per mile). That's around 1,030,000 feet divided by 11,568,480 feet, and that is a grade of 8.9%. Let's round that to 9%. Nine squared is 81. One hundred squared is 10,000. Add those. You get 10,081. Take the square root of that. You get 100.4 (with rounding). That means you hike an extra four tenths of a mile for every 100 miles you hike. Multiply that four tenths by 21.91 (the number of 100 mile legs in the 2191 mile trail) and you get about 8.75 miles of added distance.

Excellent breakdown Map Man!!! Good stuff.

Another Kevin

04-18-2018, 17:03

the miles added by elevation change is insignificant vs the effort added

I have said before, measuring the trail by units of effort with multipliers for weather etc would be a great tool for nerdy overplanners

I remember how Nimblewill Nomad on his journal rated trail difficulty in units of "Snickers bars." Then he got to NH and gave up on his rating system.