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#41412 - 01/16/15 11:31 AM Re: 14,508: Mt Whitney Elevation [Re: saltydog]
dethMarch Offline


Registered: 06/30/11
Posts: 18
Loc: SLO
This reminds me of a conversation I had with a colleague years back, who was working in geomapping, with some very sensitive GPS equipment. She shared a shocking fact with me, that any given point on the earth's crust, is flexing up and down on a daily basis, mostly due to tidal forces - (sun and moon gravitational forces, and also in response to ocean tides). Depending on what the ground is made of, local faults, etc, it can be as much as a few centimeters. Most geological survey data doesn't take this into account, except as a "margin of error" baked-in to permanent measurements.

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#41439 - 01/18/15 02:19 PM Re: 14,508: Mt Whitney Elevation [Re: dethMarch]
SierraNevada Offline


Registered: 09/05/11
Posts: 1134
Loc: NorCal
This is really interesting stuff, DethMarch. Its like our planet is breathing with tides. Did you perhaps mean millimeters per day instead of centimeters? I didn't realize the earth's surface fluctuated vertically so much.

Surveying for vertical control is based on leveling back to the previous benchmark, which is within eyesight, so both points move up or down about the same amount. So the fluctuations you're describing are not detectable between points close together using standard survey methods. GPS, based on satellite measurements with a global perspective can measure the up and down movement of both points, or any point for that matter.

GPS has allowed measurement of uplift of mountain ranges, fault slip, and tectonic drift. One way this is used is in predicting the probability of an earthquake on a particular fault. The chance of an earthquake occurring is based on an average annual "slip." The horizontal movement builds up stress over the years, and then lets go suddenly.

The most active reaches of the San Andreas fault move horizontally about an inch per year, and when it lets go, it can offset up to 30 feet near the epicenter. Here's a paper describing how they measure the slip rate with GPS.

Here's a paper comparing a leveling survey network with GPS measurements in Poland.

Edited for more detail and to add another link.


Edited by SierraNevada (01/19/15 07:58 AM)

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#41612 - 01/27/15 04:21 PM Re: 14,508: Mt Whitney Elevation [Re: SierraNevada]
dethMarch Offline


Registered: 06/30/11
Posts: 18
Loc: SLO
In most places, millimeters. In *some* places, centimeters. (was my understanding).

Some of that also has to do with tides bringing water into the water table (and back out) on a daily basis, which causes expansion and contraction as well. I think Whitney would more likely be millimeters. Because; granite.

I should write a grant proposal to get funding to bring one of those fancy $10,000 GPS receivers up there, to collect data for a few days. Not that that would settle any arguments. laugh


Edited by dethMarch (01/27/15 04:21 PM)

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#41616 - 01/27/15 08:36 PM Re: 14,508: Mt Whitney Elevation [Re: dethMarch]
Steve C Offline


Registered: 09/22/09
Posts: 7556
Loc: Fresno, CA
> I should write a grant proposal to get funding to bring one of those fancy $10,000 GPS receivers up there, to collect data for a few days.

DO IT! You will get help from the hiking community!

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#53724 - 06/28/18 12:33 PM Re: 14,508: Mt Whitney Elevation [Re: Steve C]
Steve C Offline


Registered: 09/22/09
Posts: 7556
Loc: Fresno, CA
Updating this thread... Just curious to see whether anything has been updated or changed.

NGS (National Geodetic Survey) has an updated "Survey Marks and Data Sheets" web page, with links to an interactive map: NGS Data Explorer

Using the explorer map and zooming in on Mt Whitney, we can find the highest elevation data sheet: PID : GT1809

That Data Sheet shows the elevation of 14508.

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#53741 - 06/30/18 04:44 PM Re: 14,508: Mt Whitney Elevation [Re: Steve C]
SierraNevada Offline


Registered: 09/05/11
Posts: 1134
Loc: NorCal
14,508 ft is only 0.021% higher than 14.505 ft, relative to sea level, which is the hikers perspective. By surveying standards, this is a HUGE discrepancy over the relatively short horizontal distance involved. So what government agency is going to overcome the logistical and funding challenges to get the world a reasonable answer? Will a private company step up? Does anybody really care?

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#53743 - 06/30/18 05:45 PM Re: 14,508: Mt Whitney Elevation [Re: SierraNevada]
Steve C Offline


Registered: 09/22/09
Posts: 7556
Loc: Fresno, CA
As you're well aware, SN, there is a much worse and more pressing problem lying all over the Whitney Zone, and we've been waiting and hoping a government agency would "overcome the logistical and funding challenges to get the world a reasonable answer... Does anybody really care?"

We sure do care, but I'm not sure about the others.

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#53747 - 07/01/18 09:17 AM Re: 14,508: Mt Whitney Elevation [Re: Steve C]
SierraNevada Offline


Registered: 09/05/11
Posts: 1134
Loc: NorCal
Steve, I can only guess what problem is lying all over the Whitney Zone. Does it come in a plastic bag and smell like crap? Its peak season, and I'm sure people will start bringing it up again. There's a new technological breakthrough ( toilet tech ) that seems to be working well under similar conditions as Whitney. There's reason for hope.


Edited by SierraNevada (07/01/18 12:40 PM)

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#53787 - 07/04/18 08:46 PM Re: 14,505 or 14,508 -- Mt Whitney Elevation? [Re: AxeMan]
Eugen Offline


Registered: 01/01/18
Posts: 4
Loc: Oregon
In world system it is ONE METER. How cares?

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#53799 - 07/05/18 10:40 PM Re: 14,505 or 14,508 -- Mt Whitney Elevation? [Re: Eugen]
skiroc Offline


Registered: 09/08/12
Posts: 6
Loc: Cal
I've been communicating with the NGS Geodetic Advisor for the SW Region about this topic over the Spring and hope to discuss with him next week during a conference we will both be attending.

He has provided a lot of history and info on why there are so many published elevations, it is clearly a topic he is both professionally and personally interested in. In summary he makes two points:

- 14,500 ft is the most "defensible" value for Mt. Whitney using current benchmarks and datums, but the highest point of the peak is likely higher

- there will be new datums in 2022 so the references for both lat/long and elevation will be changing - Whitney and other elevations will be decreasing by (estimated) a little under 3 feet

I'll report back if I learn more.


Edited by skiroc (07/05/18 10:42 PM)

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#53809 - 07/08/18 07:46 PM Re: 14,505 or 14,508 -- Mt Whitney Elevation? [Re: skiroc]
SierraNevada Offline


Registered: 09/05/11
Posts: 1134
Loc: NorCal
The should sell t-shirts and other swag with velcro numbers to keep up with these changes.

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#53847 - 07/11/18 10:40 AM Re: 14,505 or 14,508 -- Mt Whitney Elevation? [Re: SierraNevada]
cantare Offline


Registered: 04/07/14
Posts: 17
Loc: California
What I love most about this whole elevation debate is the 1930 NPS plaque installed by someone lacking an understanding of significant figures: "14,496.811 Ft". That's an implied precision of 0.3 millimeters, or the size of a small grain of sand. laugh

Also waiting for some sufficiently large group of burly DIYers to stack, upend, or reorient any of the most prominent boulders just to mess with people. What constitutes the "summit" of a loose rockpile?

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