Map miles vs. actual miles

[timcar86]

I'll be making a trip from Clingman's Dome to Fontana Dam in April. I have an argument with my friend that says due to elevation change, we'll be walking more like 60 miles instead of 30. So what's the deal? I plan on spending 3 days on the trail and I expect to make it in that time. I realize that the hike will be strenuous and I've been training for it. Is 30 miles in 3 days unrealistic?

[Lone Wolf]

it's 32 miles. not 60. yes you can do it easily in 3 days.

[rafe]

AT distances, as listed in the guidebooks, are distance-over-ground.

Furthermore, in spite of appearances, the verticals don't add much to the distance. Eg, what most thru-hikers would consider an "extremely steep" grade is typically no more than 20% -- ie., 1000 feet of gain in 1 mile. A more typical grade is 1/2 or 1/3 of that.

The profiles shown on the ATC maps generally have enormous vertical exaggeration. 5 to 1 is common, and sometimes it's higher.

[Johnny Thunder]

I'll be making a trip from Clingman's Dome to Fontana Dam in April. I have an argument with my friend that says due to elevation change, we'll be walking more like 60 miles instead of 30. So what's the deal? I plan on spending 3 days on the trail and I expect to make it in that time. I realize that the hike will be strenuous and I've been training for it. Is 30 miles in 3 days unrealistic?

HAHAHAHAHAHAHAHAHAHAHAHAHAHAHA

This has been a pet peeve of mine since I first took my orientation merit badge courses. Geometry tells us that the airial distance shown in maps is incorrect when it comes to the actual mileage of terrain due to changes in elevation.

Funny thing is that I seriously just had this conversation on Friday night with a guy who worked for Google maps. He confirmed that maps were inherently wrong when it came to actual distance. The GMaps project takes GPS distance and elevation readings something like every 5 yards (Friday was a bit hazy). After that it uses these readings to calculate the actual distance you've traveled.

He imagined that when a mapmaker publishes a map that the distances listed are actual distances and not map distances.

Hope that makes sense.

I wouldn't think that you'd be traveling 60 miles over 30...that seems like a lot. See if you can add up the total number of feet gained and the number of feet lost in elevation. Then use that figure as the vertical for figuring out the hypotenuse (spelling?) of the triangle.

[timcar86]

That's good to hear, I'll send him this page.

[rafe]

See if you can add up the total number of feet gained and the number of feet lost in elevation. Then use that figure as the vertical for figuring out the hypotenuse (spelling?) of the triangle.

When you do that, you'll see that the error is fairly small, typically on the order of 5%. In any case, the distances cited in the AT data books are accurate. They're measured with a wheel. They're distance-over-ground.

[Johnny Thunder]

When you do that, you'll see that the error is fairly small, typically on the order of 5%. In any case, the distances cited in the AT data books are accurate. They're measured with a wheel. They're distance-over-ground.

Exactly...1000 feet of elevation loss/gain only tacks on an extra 93 feet of walking over the course of a map mile.

[Appalachian Tater]

In other words, the distance measured between two points on a map is less than the distance listed in the guidebooks. And when Google maps gives directions and milage it takes this into account as well?

[hopefulhiker]

One thing you have to consider is the little bit of extra walking you do to get to a water source or to get to a town....

[Johnny Thunder]

Also, those 30 miles might "feel" more like 60 if you compared them to the 30 miles in Maryland....or 30 miles in Ohio. Maybe it's just me and I'm out of shape...

[wrongway_08]

Just go off the map miles, you'll be fine.

[Rain Man]

The Pythagorean theorem states that the square of the hypotenuse is the sum of the squares of the other two sides, that is,

c2 = a2 + b2 (those "2s" should be superscripted)

If he says you're traveling 60 miles up and down over a 30 mile "base line", then 60 squared equals 30 squared plus "x" squared. "X" being your rise (and fall). You should be able to calculate it as two equal back-to-back triangles, to allow for equal rise and fall for a rough calculation.

If my math is correct, you'd have to climb (and/or descend) 52 vertical miles from Newfound Gap to Fontana Dam in order to travel 60 "straight line" miles.

I don't think so. People who ascend Mt Everest climb less than 5 miles.

BTW, fat old ME did the Fontana-to-Newfound Gap hike NOBO in two and a half days, so I sure bet you can do it SOBO in three, for sure.

RainMan

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[wrongway_08]

- What..... I'll take your word on that

[rafe]

Bottom line is, the figure from Google maps (or a GPS) could be off by a few percent. The figures from the ATC maps and guides are accurate.

[Digger'02]

those distances have been recorded with a wheel an upheld with thousands of foot travelers. trust the maps, the data book and the companion

[rafe]

- What..... I'll take your word on that

Let me try to illustrate this simply. Take a ruler. 1 foot long, right? OK, leave one edge on your desk and raise the other end one or two inches. The horizontal distance "covered" by the ruler hasn't changed by much. The actual slope of the AT, over long distances, is rarely greater than 20%, and even 20% (over the course of a mile) feels like an "extreme" grade.

[Benjy]

Yea what them people said that must of been Mustang saying that .

[Scaper]

Someone in Warrens group measured the entire trail with a wheel one year.

[JAK]

I think he said more 'like' 60 miles than 30 miles. I figure a net elevation gain of 1 mile is equivalent to an additional 10 miles horizontal, so for 30 miles to be equivalent to 60 miles you would only need a cumulative elevation gain of about 3 miles. Assuming equal ups and downs that would be an average grade of 3 in 15, or about 20%. That is steep, but not completely unheard of in particularly uppy downy terrain. The trail surface can make a real difference also, like if there is alot of stumps and hollows, or sand or mud or snow.

[Beachcomber]

The Pythagorean theorem states that the square of the hypotenuse is the sum of the squares of the other two sides, that is,

c2 = a2 + b2 (those "2s" should be superscripted)

If he says you're traveling 60 miles up and down over a 30 mile "base line", then 60 squared equals 30 squared plus "x" squared. "X" being your rise (and fall). You should be able to calculate it as two equal back-to-back triangles, to allow for equal rise and fall for a rough calculation.

If my math is correct, you'd have to climb (and/or descend) 52 vertical miles from Newfound Gap to Fontana Dam in order to travel 60 "straight line" miles.
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Never did cotton to that book-larnin' no-how. We're out in the woods so we won't have to do math OR spelling.