High Sierra Topix

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 ....[/quote]



Why?


Does it really matter? I mean, if you think about it there's no way to track every single little up and down you cover over 200 miles... Even if someone hiked it with a well calibrated altimeter, it would still just be an estimate..

Not trying to question you, just feeling a little philosophical

DavePloessel wrote:Does it really matter?

No, nothing really matters.... or maybe it does. I'm not sure.

But in the mean time, I'm amusing myself in various ways.

HikeSierraNevada wrote: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)...

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.

The problem with topo maps is how does one plot the course? I have the National Geographic TOPO software and it is horrible for estimating distance because you can't easily follow a trail with it. So I don't trust the elevation totals either.

Altimeters are subject to errors due to changes in the barometer as well as the thermometer.

GPS elevation values are rather poor in quality. One approach is to use the X/Y values which are more accurate and a map dataset to determine the elevation. This works pretty well, but there is still a problem since the X/Y error can result in significant elevation error. For example, if you're walking a flat trail next to a cliff and the X/Y error puts you on the cliff, then back near the trail, then back on the cliff, you get a huge elevation gain that is simply an artifact.

Combining altimeter and GPS might be the best, but it's beyond what little I know about the subject, which is already more than I ever wanted to know.

I just wanted a reasonably accurate number. But apparently it isn't known and that surprises me.

What is the point? None really, just interested.

Float that question over at the JMT yahoo group. There are a lot of "gearheads" over there. I bet someone has GPS'ed it!

FWIW. Someone over at JMT Yahoo tallied Wenk's waypoints in her JMT book 42,773- HI to Whitney summit.

John Dittli wrote:FWIW. Someone over at JMT Yahoo tallied Wenk's waypoints in her JMT book 42,773- HI to Whitney summit.

John, thanks for posting over there on my behalf.

I responded on Yahoo and maybe it doesn't make sense to cross-post, but here is a summary of the values I have obtained so far for the total elevation gain for Yosemite to Mt. Whitney (in thousands of feet):

46.0 - Wikipedia
46.9 - TOPO!
42.8 - "Wenk's waypoints"
77.7 - Parkay Maps GPS elevation data (unfiltered)
56.8 - Parkay Maps GPS XY data, converted via GPS Visualizer
55.0 - Altimeter watch accumlator from friend who walked JMT + detours