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Maps, Signs, and reality

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Maps, Signs, and reality

Postby balzaccom » Wed Sep 19, 2012 11:12 am

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.
Balzaccom

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Re: Maps, Signs, and reality

Postby giantbrookie » Wed Sep 19, 2012 7:21 pm

This reminds me of a series of roadsigns of I5 north of the 505-I5 junction. I don't know if those signs are still there but there were two consecutive road signs spaced over several miles that certainly contradicted each other. Let's say the second one would imply that the destinations were moving north faster than the car.

I can recall other cases of discrepant mileages and totals on other trails, but I don't recall exactly which ones. All of those memories were overshadowed by one unforgettable one (has been fixed since). This was the trail from Blue Lake to Dingleberry Lake. As recently as 1983 this trail had this absurd winding track including one enormously long hairpin loop that went down one side of a gully and back up to the other with no more than 100 yards of separation at the top (and a total distance that felt like over a half mile). This was merely the greatest of the insults along this stretch of trail. An old wood sign at Blue Lake read Dingleberry 1 mile, an estimate probably short by a factor of two. Someone before me, no doubt feeling the same degree of frustration had carved in a zero after the "1".

Regarding the map deal, I suspect the funny trail situation is on the Tom Harrison map. If you compare the trails on the Harrison map to the USFS John Muir Wilderness/Seki topo I've found the trails in that area to be accurately reflected on USFS version but not on the Harrison. I seem to recall this difference between two maps (Harrison vs USFS) in a few other places as well, such as the Woodchuck Country.
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Re: Maps, Signs, and reality

Postby RoguePhotonic » Thu Sep 20, 2012 2:24 pm

I have noticed this problem with a great number of signs around the Sierra. When you start the High Sierra Trail it's really bad. sometimes as much as 20 miles off.
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Re: Maps, Signs, and reality

Postby paul » Thu Sep 20, 2012 7:55 pm

The worst seem to be Forest Service signs. The national parks are a little better in my experience. I have seen Forest Service sings where the posted mileage to a destination actually increases as you approach it. Which is why I sometimes refer to "Forest Service miles" as opposed to to real world miles. Their signs are good for directions only. Take the mileages with a large pinch of salt.
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Re: Maps, Signs, and reality

Postby oleander » Mon Sep 24, 2012 4:09 pm

I admit I am pretty reliant on the Tom Harrison maps.

Anyone offer an opinion on their mileage accuracy?

The only obvious problem I've had with a Harrison map is with the Hoover Wilderness one. There is a section of trail where the Harrison mileage seemed way off.

It would be fun to learn a little more history and context on map-making, to understand where and how errors occur and how they are or are not corrected.

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Re: Maps, Signs, and reality

Postby paul » Mon Sep 24, 2012 4:46 pm

The Tom Harrison Maps always seem pretty reasonable on their mileages in my experience.
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Re: Maps, Signs, and reality

Postby cmon4day » Mon Sep 24, 2012 5:51 pm

On my recent trip to Emigrant Wilderness, the new signs there didn't post mileage, they just pointed you in the right direction. The post would have an arrow and a name (Long Lake, Wire Lakes, Whitesides Mdw, etc.) That worked for me since I already knew about how far is was anyway.
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Re: Maps, Signs, and reality

Postby MountainMinstrel » Mon Sep 24, 2012 5:54 pm

paul wrote:The Tom Harrison Maps always seem pretty reasonable on their mileages in my experience.


I agree. The only issue I have had with a Tom Harrison map is the Yosemite High Country Trail map. While the mileage seems accurate the elevation contours have been very inaccurate.
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Re: Maps, Signs, and reality

Postby oleander » Tue Sep 25, 2012 7:55 am

MountainMinstrel wrote:
paul wrote:The Tom Harrison Maps always seem pretty reasonable on their mileages in my experience.


I agree. The only issue I have had with a Tom Harrison map is the Yosemite High Country Trail map. While the mileage seems accurate the elevation contours have been very inaccurate.


That's interesting. Which specific regions of Yosemite seem to be poorly represented (contour-line wise) on the Tom Harrison map? And that also begs the question: What does Harrison himself use as his source maps? (That implicates the source maps, too.)

Not really being critical, just curious. Mapmaking is an insanely tedious job.

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Re: Maps, Signs, and reality

Postby AlmostThere » Tue Sep 25, 2012 9:12 am

A friend told me he met Harrison out on the trail, pushing a wheel to measure the miles.

All commercial maps use USGS maps as their base map.
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