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Maps and how to use them?
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Paul Wagner
(balzaccom) - F

Locale: Wine Country
Maps and how to use them? on 09/19/2012 13:09:54 MDT Print View

On our last trip, we had some fun comparing data with reality. Let's start with the signs marking the various trails we hiked. At Twin Lakes, we started up towards Silliman Pass at a sign that indicated it was 1.3 miles away. Off we went.

When we got down to the other side of the pass, we found another sign. This one told us that Silliman Pass was 2.0 miles back up the trail...and that Twin Lakes was 3.0 miles away.

So at least in this case, 1.3 + 2.0 = 3.0. And we found other cases that were similar. It's almost as if the people making and placing the signs really never looked at what they were doing.

Too bad we can't use that kind of math to resolve the federal deficit. (By the way, our map had completely different mileages for each of these legs, so the real distance really is still anyone's guess.)

When you combine that with a beautifully maintained trail we took that wasn't on the map, and another trail we took that was on the map but was only a rough route that petered out completely on the ground; it all just serves to warn you that the difference between what you see on the maps and signs may not accurately reflect reality on the ground.

That's not to say you shouldn't take a map! We never travel with maps, and often with various scales and verions. On this trip we ended up using ours extensively to figure out how to get out of the deadfall mess that the missing trail had led us into.

And it worked.

And if it hadn't we could have still use the map to start a fire and keep warm.

Maps are good. You just can't always trust them.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Maps and how to use them? on 09/19/2012 13:18:47 MDT Print View

Yes, I remember running into something crazy like that on Silliman Pass heading over toward Ranger Lake. I never figured out what they did wrong. On other trails, if you study the errors, you can see that they got all of the numbers right, but they interchanged the position of two trail signs. That will cause lots of headaches.

Sometimes those areas have forest fires. After the fire is out and they want to restore the trail for use, they decide to realign it. That will change the mileage a little. Sometimes it changes a lot.

I met a gal working for USGS and NPS, and she had just completed solo surveying of the Red Peak Pass Trail in the Clark Range of Yosemite. I think it took her a week or ten days, but she had everything chained to the nearest few inches for every switchback. This was in the time before GPS. Now it would be done with a survey-grade GPS receiver, but it still takes a lot of time to do it right.

A good updated map is a life-saver.


Hk Newman
(hknewman) - MLife

Locale: Western US
Re: Maps and how to use them? on 09/19/2012 13:26:27 MDT Print View

Maps can hide features within their contour intervals, so a smaller scale is often needed. Then more maps are needed which cost more money and they will not likely reflect trail maintenance (or the lack thereof). Drawback of maps can't really be helped. A detailed trip report could help but takes out the mystery.

Eric Lundquist
(cobberman) - F - M

Locale: Northern Colorado
Re: Maps and how to use them? on 09/19/2012 13:30:48 MDT Print View

Most of the trail mileages that I've come across to not take into account elevation change. Some of the time this isn't an issue and they're pretty close but other times, especially in mountainous terrain, the mileages could be off by half a mile or so.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Maps and how to use them? on 09/19/2012 15:03:24 MDT Print View

> Maps can hide features within their contour intervals, so a smaller scale is often needed.


And some older topo maps are absolute gold stars here. We had to get off a ridge which proved impossible (too much scrub, no water), so I picked a side spur which looked reasonable. The end sloped gently down to the river - on the topo. Reality was, when we got to the end of the spur, that there were 50+ m cliffs ALL around the end of the spur. The map makers had not looked closely enough at the aerial photos.

Actually, this problems exists over a bunch of maps in this general area. Rule of thumb now is that a contour line means a cliff, possibly serious.


Stuart R
(Scunnered) - F

Locale: Scotland
Re: Re: Re: Maps and how to use them? on 09/19/2012 15:34:24 MDT Print View

I remember as a youth hiking up to a small lake shown on my map with the intention of doing some fishing. When I got there all I found was a flatish area covered in 2ft pine trees - the lake had obviously burst its bank years previously...