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Re: Need a trail mileage

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avatar Need a trail mileage
September 21, 2012 10:48AM
I've been poking around on the internet trying to determine a trail mileage without much luck. I've found several depictions of the trail plus trip reports but nothing with specific mileages. I'm trying to determine the actual mileage from Agnew Meadows trailhead up the River Trail to the Shadow Lake Trail intersection just above Olaine Lake. I'm guessing about 3.5 miles but would like to know the precise distance. I've got mileages from Olaine Lake to Lake Ediza but just can't nail down that first leg. Anybody know?

Jim
Re: Need a trail mileage
September 21, 2012 12:52PM
To find any trail distances as long as the physical trail and map trail are similar, one can simply measure distance with a ruler against a map.

http://mapper.acme.com/?ll=37.68851,-119.11021&z=15&t=T

I just measured that trail as 2.4 miles with a ruler against my monitor here at my workplace. I've measured that trail many times on a paper USGS topo to be 2.0 miles from the AM trailhead to the south end of Olaine Lake and just got the same result. The published values are often no more accurate. How do you think published mileages are generated? All with rolling surveyor's wheels? On rocky mountainous trails, surveyors wheels are not going to be any more accurate than simply measuring against a topo. Trails that have lots of switchbacks that are not accurately drawn on maps are an issue. But that trail has no serious turns. I measure trails all the time in trip planning at 1/4 mile increments, penciling tick marks along trails, and have been doing so for decades. But actually do not use a ruler but rather the edge of a piece of 1 mile long paper marked at 1/4 mile increments. Works better for windy trails and switchbacks. Pretty much match values Wilderness Press comes up with in their guides.



http://www.davidsenesac.com
avatar Re: Need a trail mileage
September 21, 2012 01:04PM
David,

Thank you. I was not familiar w/ ACME Mapper 2.0 and I had no physical map in my possesion on which to measure it. I normally use Natl Geo Trails Illustrated maps but they don't cover that spot. As for steep switchbacks I've noticed Natl Geo does account for the mileage fairly accurately although I don't know how they accomplish it.

Jim
Re: Need a trail mileage
September 21, 2012 07:46PM
Quote
tomdisco
David,

Thank you. I was not familiar w/ ACME Mapper 2.0 and I had no physical map in my possesion on which to measure it. I normally use Natl Geo Trails Illustrated maps but they don't cover that spot. As for steep switchbacks I've noticed Natl Geo does account for the mileage fairly accurately although I don't know how they accomplish it.

Jim

When topozone.com began and produced several Caifornia map products, they had a trail measuring tool that could measure colored lines one would draw as an overlay on their maps. I used it in several places I'd actually hiked and found the results of both mileage and vertical up/down rather incorrect. Thus phoned up the company and reached one of the software engineers that related the positional and elevation data base was not based on the data the map displayed but rather the early USGS digital data system. Somehow that caused otherwise direct lines to wobble back and forth as it connected to the digital points. The result was the mileage and vertical were both higher than it should have been.

I am not familiar with the current state of mapping software automated distance and vertical calculations but I'm sure given GPS and the considerable digital mapping applications today that there are probably canned aps that can measure the length of any drawn line regardless of bends and turns. Simply a matter of adding up incremental short straight line distances at the map resolution. But I would not trust any such application until I had proof it was reasonably accurate.



http://www.davidsenesac.com
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