PDA

View Full Version : Map miles vs. actual miles



timcar86
02-26-2008, 14:09
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
02-26-2008, 14:14
it's 32 miles. not 60. yes you can do it easily in 3 days.

rafe
02-26-2008, 14:15
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
02-26-2008, 14:21
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
02-26-2008, 14:25
That's good to hear, I'll send him this page.

rafe
02-26-2008, 14:28
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
02-26-2008, 14:31
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
02-26-2008, 14:31
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
02-26-2008, 14:41
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
02-26-2008, 14:52
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
02-26-2008, 15:03
Just go off the map miles, you'll be fine.

Rain Man
02-26-2008, 15:05
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.

Rain:sunMan

.

wrongway_08
02-26-2008, 15:26
http://anchoredbygrace.com/smileys/headscratch.gif - What..... I'll take your word on that :D

rafe
02-26-2008, 15:27
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
02-26-2008, 15:36
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
02-26-2008, 16:38
http://anchoredbygrace.com/smileys/headscratch.gif - What..... I'll take your word on that :D

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
04-06-2008, 15:49
:-? Yea what them people said that must of been Mustang saying that :p.;)

Scaper
04-06-2008, 16:09
Someone in Warrens group measured the entire trail with a wheel one year.

JAK
05-05-2011, 16:01
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
05-05-2011, 17:18
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.
.

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.

Wise Old Owl
05-05-2011, 17:41
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.

Doesn't hold true when you are not on the AT, there have been times where the GPS says .6 back to the lot and a wooden sign says 1 mile!

tolkien
05-05-2011, 18:00
http://anchoredbygrace.com/smileys/headscratch.gif - What..... I'll take your word on that :D

x^2 + 30^2 = 60^2
x^2 + 900 = 3600
x^2 = 3600-900 = 2700
x = square root of 2700
x = 51.92

Dogwood
05-05-2011, 18:34
It's wheeled!!! Someone wallks with a hand held wheel that converts on ground distance to miles, as Terrapin stated.

....People who ascend Mt Everest climb less than 5 miles. - Rainman

Think about this! STOP! Think about this! ^^^

Carl in FL
06-07-2011, 18:53
A flat mile is 5280 map feet and 5280 travel feet.
A 20% grade that is 5280 map feet is about 100 feet longer in travel.
That's about a 2% difference. It tells you essentially nothing though.

Slo-go'en
06-08-2011, 12:17
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?

Figuring out distances from maps using a ruler gives you the straight line distance between points, which is fine if the path between those two points is indeed a straight line - which it rarely is.

Therefore, to know what the exact distance between those points are, someone would have had to physically measure the distance on the ground. Which has been done for all roads and major trails. This actual measured distance is often marked between selected points on maps.

No doubt google maps has access to the measured distance data base and uses that when calculating distance for directions.

snick
07-28-2012, 11:05
Figuring out distances from maps using a ruler gives you the straight line distance between points, which is fine if the path between those two points is indeed a straight line - which it rarely is.

Therefore, to know what the exact distance between those points are, someone would have had to physically measure the distance on the ground. Which has been done for all roads and major trails. This actual measured distance is often marked between selected points on maps.



There are problems with maps that depict three dimensional surfaces on a hlat surface, and there is also a problem with scale and the relationship between the line on a map and the trail in the woods. If you are scaling distances on a map and the map has a large scale, then you are missing many of the small curves that are on the ground. I was surprised to see that the A.T. has been measured with a wheel. I guess that it was a way for someone to get paid to take a vacation. Wheels are inherently inaccurate, because the wheel doesn't measure all of the surface; it only measures what it has touched.


I doubted the accuracy of A.T. map distances from day one, but I realized that such impressions are rather subjective. Then I noticed that some sections agreed with my impression, and those pieces were straight and even. Then there was the day in Connecticut when it took me five hours ttravel 2.8 miles, and the next day was worse: it took me more than an hour to cover 0.3 miles. That's 1584 feet; I can throw a stone almost a fifth of that distance, and it took me an hour to walk it. The map distances are just wrong.

Retro
07-28-2012, 15:52
I've always believed that the constant side-stepping of obstacles such as roots, rocks, and blowdowns also adds quite a bit of mileage to the trek since it's more like zig-zagging along the trail than walking in a straight line. Try and measure that.

Pedaling Fool
07-28-2012, 16:22
There are problems with maps that depict three dimensional surfaces on a hlat surface, and there is also a problem with scale and the relationship between the line on a map and the trail in the woods. If you are scaling distances on a map and the map has a large scale, then you are missing many of the small curves that are on the ground. I was surprised to see that the A.T. has been measured with a wheel. I guess that it was a way for someone to get paid to take a vacation. Wheels are inherently inaccurate, because the wheel doesn't measure all of the surface; it only measures what it has touched.


I doubted the accuracy of A.T. map distances from day one, but I realized that such impressions are rather subjective. Then I noticed that some sections agreed with my impression, and those pieces were straight and even. Then there was the day in Connecticut when it took me five hours ttravel 2.8 miles, and the next day was worse: it took me more than an hour to cover 0.3 miles. That's 1584 feet; I can throw a stone almost a fifth of that distance, and it took me an hour to walk it. The map distances are just wrong.
Dude, you can argue all you want about errors introduced in maps by various factors, but your examples are not map errors. Sounds like you just slipped into another dimension, happens all the time, just be happy that you somehow managed to slip back into this dimension. http://criticalbelievers.proboards.com/index.cgi?board=paranormal&action=print&thread=2570





;)

Biggie Master
07-28-2012, 16:23
Folks, this is much more easily understood if you simply realize that it doesn't matter if it's 31.2 miles or 32.5 miles or 33.7 miles... You will only get there by continuing to put one foot in front of the other... Are we going to start calculating the number of steps saved if we take the "low side of the track" around turns? Just keep walking until you reach your destination. Dome to Dam 3 easy days.

MuddyWaters
07-28-2012, 16:46
smokies maps have distances marked on the trails
At guidebook has correct distances too

Now, if you were talking about a grand canyon map, you could be way off trying to read just 2D distance. The GC maps caution against that.

gpburdelljr
07-28-2012, 22:01
Using the profile function on DeLorme Topo 9.0 there is a 1.6% difference in terrain miles and horizontal miles from Fontana Dam to Clingmans Dome.

BabySue
07-28-2012, 22:42
I hiked from Sugar Run Gap, VA, to Wapiti Sheter today. The guidebook mileage is short by about 1.5 miles. Conclusion: The guidebook has errors. But neither that error nor any other has been caused by measuring map miles or aerial miles as opposed to actual miles. As has been emphasized above, elevation change has accounted for. This is true of the guidebook, of www.atdist.com, and of the Trails Illustrated maps.

Wise Old Owl
07-28-2012, 22:55
Nothing new here RainMan nails the answer - I have pondered this for a few years and asked a few people smarter than me - The Old Man - dad caught me on it at a park

http://i250.photobucket.com/albums/gg275/MarkSwarbrick/GPS.jpg

Wise Old Owl
07-28-2012, 22:58
Algebra was my archelis heal and bunion... feel free to correct me - but jap programming is the culprit in the Garmin.

BabySue
07-28-2012, 23:20
Maybe the ATC should change the 2000 mile club to the 2032 club.

Wise Old Owl
07-30-2012, 09:39
But most Garmin has the topo in it, it can correct the mistake, So FYI if you are purchasing one without a base map - this is going to happen.

StealthHikerBoy
07-30-2012, 10:01
I got my geek on a bit and calculated the difference for a tough climb I am familiar with... going from the bottom of the Grand Canyon up the S. Kaibab Trail to the top. This is a 6.15 mile hike with a vertical gain of 4790 feet.
If you assume a constant grade for the climb, if you took the hill out rather than 6.15 miles the hike would be 6.082 miles. Or, about 359 feet shorter. This is pretty much the length of a football field including the end zones. You'd have to make a climb like this almost 15 times in order to add a mile to the distance because of the hill. So, if you went about 90 miles up a grade like this, it would add about 1 mile to the hike length as opposed to hiking flat.

Sure feels like a heck of a lot more when you are doing it though!

RED-DOG
07-30-2012, 10:09
What is this MATH class, it don't matter if its 30 miles or 90 miles from point A to point B it is what it is.

TheBirdman
07-30-2012, 17:36
This thread is like a time capsule... Started in 2008, randomly continued after 3 years of inactivity in 2011, randomly started after another year of inactivity in 2012. Can I leave a DVD and newspaper clipping here so people in the future know what it was like in the past?

tdoczi
07-30-2012, 21:57
This thread is like a time capsule... Started in 2008, randomly continued after 3 years of inactivity in 2011, randomly started after another year of inactivity in 2012. Can I leave a DVD and newspaper clipping here so people in the future know what it was like in the past?

and the funniest thing about it to me, is that while it is not an invalid question it is one that has a simle straightforward answer that is really not open to interpretation, debate or discussion. the mileages listed account for elevation. even if they did not the degree of inaccuracy would be miniscule. end of discussion on topic.

but some people insist on trying to argue otherwise. it reminds me of a kid in my HS physics class who would attempt to debate the teacher on the validity of the laws of physics. he just didnt believe gravity could REALLY work that way. not kidding.

tdoczi
07-30-2012, 23:06
Wheels are inherently inaccurate, because the wheel doesn't measure all of the surface; it only measures what it has touched.



ok, i was really trying to avoid asking this, but what the heck does that statement even mean exactly?

dale1627
07-31-2012, 05:29
tdoczi, I trend to agree with the statement. I can think of several areas where the wheel would not be accurate. Example, covering the rocks on the trail going from Hump mountain to 19E. Just too rough of a terrain to roll the wheel. I will say this however, my logged gps mileage was within .1 of a mile compared to the listed mileage of the Carvers Gap to 19E section. I believe that the .1 of a mile difference was from when I walked out of the tree line and saw Hump mountain Saturday evening. I promptly turned around and camped at the Bradley gap campsite.

dale1627
07-31-2012, 05:33
Please disregard my last comment. I just reread the comment in question and am now also confused by it.

Montana
08-01-2012, 11:13
Wheels are inherently inaccurate, because the wheel doesn't measure all of the surface; it only measures what it has touched.

Exactly... If you had a microscopic wheel to measure with, the distance from GA to ME would be nearly infinite! :D

bencarlinson
08-02-2012, 06:26
There is a difference will be there between the map and actual miles. Map are used mainly for directional signs and simultaneously distance about the area also. A treasure map is drawn to a scale of 2 inches = 3 miles, like-wise different types of maps are available according to the needs and specification areas also. Please produce some more attachments about the topic for view detail information.

snick
08-02-2012, 14:31
That means that wheels can't be trusted to measure anything except for a flat surface, no bumps and no depressions.

Pedaling Fool
08-02-2012, 15:27
The wheel not completely going over (touching) every inch of rocky surface area is a non-issue, since our feet also don't touch every inch of rocky surface area we walk over. And if one were to shoot a laser from point A to B it (the lasar) would not measure all the surface area it passes over, not to mention it wouldn't even measure the zig-zags.

tdoczi
08-02-2012, 18:57
The wheel not completely going over (touching) every inch of rocky surface area is a non-issue, since our feet also don't touch every inch of rocky surface area we walk over. And if one were to shoot a laser from point A to B it (the lasar) would not measure all the surface area it passes over, not to mention it wouldn't even measure the zig-zags.

but but but BUT the maps HAVE to be WRONG! I just KNOW it!!!!!!!!!!

Razor
08-03-2012, 18:37
Just keep thinking that and ask the rest of us on the trail what the distance is,and we will give you the correct answer by reading the maps!

tdoczi
08-03-2012, 18:55
Just keep thinking that and ask the rest of us on the trail what the distance is,and we will give you the correct answer by reading the maps!

a) i think "how much farther?" is the dumbest question on earth. b) if you read more than my last post i was being VERY facetious.

wnderer
08-03-2012, 20:13
Check out the coast line paradox http://en.wikipedia.org/wiki/Coastline_paradox

Basically it says you can't really measure something like a coastline or a trail. The length of the trail will always depend on the length of the ruler you use to measure it. For example we could just draw a straight line from the beginning to the end of the trail, but that would be too short because the trail is wiggly. We could draw a line to the midpoint and from the midpoint to the end and our measurement would get longer. We could continue to break it into quarters, eighth, sixteenths etc. and the trail would always get longer. As the ruler gets smaller and smaller the length of the trail does not converge to any specific length. Now I know a trail isn't a fractal so it won't be infinitely wiggly, but for our purposes the smallest ruler we use is the length of a human pace. Even with the wheel measurements they have to be careful not have it move too serpentine over the trail but have it mimic a human's walking pace or their measurement would be too long.

Wise Old Owl
08-03-2012, 20:36
I work with two wheels to measure houses physical perimeter for termite treatment. As I measure the front vs the back often I am off by 1 foot due to terrain or mulch or some object. Wheels are to get close to the truth, pedometers are USELESS Jokes.

We have had several jobs that have blown up into full arguments with staff over wheel vs Google Earth from practical experience. It has cost me a friendship at work. Everyone wants to be right - just because you think you are right.... doesn't mean you are.

Yea I like this thread.. because it calls out a goofy fact of oops!

gpburdelljr
08-03-2012, 22:36
Who cares? Just get out and hike.

kelvinsmar
09-26-2012, 04:40
I had gone through the post. There is a difference will be there between the map and actual miles. Map are used mainly for directional signs and simultaneously distance about the area also. A treasure map is drawn to a scale of 2 inches = 3 miles, Basically it says we can't really measure something like a coastline or a trail. The length of the trail will always depend on the length of the ruler we can use to measure it, like-wise different types of maps are available according to the needs and specification areas also. Could you please provide some more attachments about the topic.

tdoczi
09-26-2012, 06:43
I had gone through the post. There is a difference will be there between the map and actual miles. Map are used mainly for directional signs and simultaneously distance about the area also. A treasure map is drawn to a scale of 2 inches = 3 miles, Basically it says we can't really measure something like a coastline or a trail. The length of the trail will always depend on the length of the ruler we can use to measure it, like-wise different types of maps are available according to the needs and specification areas also. Could you please provide some more attachments about the topic.


oy, not again already.

tdoczi
09-26-2012, 06:46
I had gone through the post. There is a difference will be there between the map and actual miles. Map are used mainly for directional signs and simultaneously distance about the area also. A treasure map is drawn to a scale of 2 inches = 3 miles, Basically it says we can't really measure something like a coastline or a trail. The length of the trail will always depend on the length of the ruler we can use to measure it, like-wise different types of maps are available according to the needs and specification areas also. Could you please provide some more attachments about the topic.


wait 6 weeks, sign up with a new username and try your post again? interesting technique.

hikerboy57
09-26-2012, 07:21
the maps are wrong I'm staying home.

coach lou
09-26-2012, 07:28
the maps are wrong I'm staying home.

Andy, your holding it upside-down!:D

hikerboy57
09-26-2012, 07:36
but my compass needle is pointing South instead of North.

coach lou
09-26-2012, 07:39
but my compass needle is pointing South instead of North.

Ozjacko is in big trouble next spring!

tdoczi
09-26-2012, 08:39
but my compass needle is pointing South instead of North.

a friend of mine once stated to me his belief that "north is always behind you."

hikerboy57
09-26-2012, 09:04
I would strongly advise him never to head west.

swjohnsey
09-26-2012, 09:20
It is only 1,116 map miles from Springer Mountain to Mount Katahdin, we're gettin' screwed!