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Total elevation gain JMT

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Total elevation gain JMT

Postby longri » Mon Jun 17, 2013 10:46 am

Has anyone here measured (altimeter or GPS or ?) or know of a measurement of the total elevation gain of the JMT?



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Re: Total elevation gain JMT

Postby maverick » Mon Jun 17, 2013 12:48 pm

HST= Wilderness Adventurer who knows no bounds, except for their own imagination.

Have a safer backcountry experience by using the HST ReConn Form 2.0, named after Larry Conn, a HST member: http://reconn.org
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Re: Total elevation gain JMT

Postby Wandering Daisy » Mon Jun 17, 2013 1:09 pm

OK, I am not good at math, but if you start in Yosemite Valley at 4,500 feet elevation and gain 46,000 feet and loose 38,000 feet, 46,000 - 38,000 = 8,000 more gain than loss. 4,500 feet + 8,000 feet = 12,500 feet elevation. Whitney Portal is a lower than 12,500 feet elevation.
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Re: Total elevation gain JMT

Postby AlmostThere » Mon Jun 17, 2013 3:22 pm

The JMT officially ends on top of Whitney, not at the Portal.
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Re: Total elevation gain JMT

Postby The Other Tom » Mon Jun 17, 2013 4:04 pm

AlmostThere wrote:The JMT officially ends on top of Whitney, not at the Portal.

Hmmm,yes,but if you start at happy isles ~4000 ft and end at the top of Whitney ~14500, then overall elevation gain is 10500. So we're still missing 2500 feet.
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Re: Total elevation gain JMT

Postby longri » Mon Jun 17, 2013 6:48 pm

The wikipedia entry (which I had checked before posting in the first place) is clearly flawed.

Surely somebody has actually measured it.
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Re: Total elevation gain JMT

Postby maverick » Mon Jun 17, 2013 7:07 pm

Summitpost has an elevation profile/graph.
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Re: Total elevation gain JMT

Postby longri » Mon Jun 17, 2013 7:41 pm

maverick wrote:Summitpost has an elevation profile/graph.


Yes, thank you, but I've seen that as well as most of the obvious such graphs that show up in a google search. I'm looking for a measured value, not one estimated by looking at the map and using the major elevation changes, not one generated by plotting the route on TOPO!, and not one merely asserted without some source.

I know people who measure almost every hike with an altimeter or GPS and the JFMT has been hiked at least twenty-nine trillion times. So surely it's been done.
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Re: Total elevation gain JMT

Postby longri » Tue Jun 25, 2013 7:38 pm

I plotted Yosemite Valley to Whitney Portal on TOPO! and got 47950 feet gain southbound and 43600 gain northbound. Then I asked a friend with an altimeter watch who had "sort of" walked the JMT with it. He had diverged in a couple of places so it wasn't a pure JMT, but he said that he got something around 55,000 feet gain (southbound).

I also came across a dataset from somebody's GPS on the web. It has about 20,000 elevation data points. That sounds like a lot but it works out to about one point every 50 horizontal feet of hiking or about 4 samples per minute at a normal pace. I tried to analyze this but lacking any signal processing knowledge I couldn't really make sense of it. I found I could get pretty much any number I wanted out of that data.

Total elevation gain is kind of a nebulous thing, a bit like asking how long the coastline of Norway is. But there should still be a reasonable answer. I know another friend who has both GPS and altimeter and says they tend to agree reasonably well.
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Re: Total elevation gain JMT

Postby fishmonger » Wed Jun 26, 2013 5:39 am

we didn't do the exact JMT but the GPS recorded 47855 feet gain. Had we taken the proper route it would have been a little more due to the roller coaster along 1000 Island, Garnet and Shadow lakes we bypassed on the much smoother PCT. Our Fish valley drop and climb to Silver pass may also have shaved a few feet off the regular route, but since we did the TM to Happy Isle in both directions, there's 2604 feet uphill to offset that.

http://didnt.doit.wisc.edu/outdoor/Muir ... g2010.html

My GPS includes a barometer and is calibrated - rarely are my elevations more than 20 feet off the posted elevations, which in some cases may not be accurately mapped anyway. Distances are really where GPS and maps disagree. I am convinced the JMT is at least 10 miles longer than what the maps and guide books tell you.
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Re: Total elevation gain JMT

Postby HikeSierraNevada » Wed Jun 26, 2013 6:02 am

longri wrote:
maverick wrote:I know people who measure almost every hike with an altimeter or GPS and the JFMT has been hiked at least twenty-nine trillion times. So surely it's been done.

If you're looking for the most accurate answer to this question, altimeter measurements is not it. Altimeters measure barometric pressure and convert it to elevation based on your last calibration point. Any changes in weather (high pressure or low pressure) throws it off considerably (up to hundreds of feet). Over the average 2-week hiking period, these errors could be quite significant. If the hiker were to calibrate the altimeter to a known topo map point regularly (several times per day), then this error can be minimized, but the calibrations tie it all back to the topo map that you wanted to avoid for some reason.

Topo map accuracy is not perfect either, but it doesn't drift on you. GPS uses either satelite calculations, a stored topo map value (interpolated), or an internal altimeter, depending on your model. The accuracy of GPS satelite calculations for vertical control (GPS elevation) is typically not as good as horizontal control, depending on the number of satelites available and quality of the receiver.

So in the end, I think you're best off using some form of topo map data if accuracy is your issue. What is the point of all this anyway, just curious.
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Re: Total elevation gain JMT

Postby maverick » Wed Jun 26, 2013 8:23 am

Hi HikeSierraNeveda,

I did no write that , Longri did. Mav
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