New elevations

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Is this really worth it?

Poll ended at Fri Dec 09, 2005 12:01 am

Yes
1
25%
No
2
50%
Maybe So?
1
25%
 
Total votes : 4

New elevations

Postby DSunwall » Mon Nov 28, 2005 4:56 pm

hey John, I just noticed that your 14er list has the old elevations, whats up with that?
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Re: New elevations

Postby John Kirk » Tue Nov 29, 2005 12:04 am

DSunwall wrote:hey John, I just noticed that your 14er list has the old elevations, whats up with that?


You have 10 days... vote if you'd like the new elevations included - in the meantime, I say maybe? :P
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Postby Layne Bracy » Tue Nov 29, 2005 10:28 am

I voted no because 1)I have only heard of updated elevations for the 14ers and wouldn't want the lists to be a mix of elevations using old and new data 2)there are no new topos out based on the new data that I know of - could be frustrating if you're trying to find point X and it doesn't exist on the maps.

Ultimately I agree to using new and improved data, but would prefer the change to be complete. Does anyone know if there are updated topo maps or updated elevations for lower peaks, too?
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Postby DSunwall » Fri Dec 02, 2005 8:30 am

I understand, and it is not really important, but just of general interest.
The only current guide book I could think of is Dave Coopers, Colorado Scrambles, he uses the new elevation for Crestone Peak and the old elevation for Sneffels. thats a start I suppose. Personally I think we should use the new elevations in our lists and just deal with the maps until they change.
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Postby cftbq » Sun May 20, 2007 3:25 pm

Use the new elevations. It will take time, but they will all become available eventually.
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Postby John Kirk » Sun May 20, 2007 7:12 pm

I think I'll refrain until quads are reprinted, because while elevation of peaks may be more accurate, the elevation of the saddles is not being updated. Why does this matter? Imagine Dallas Peak dropping to the 101st highest because Drift Peak's new elevation makes it a ranked peak (the saddle elevation didn't move up while the summit elevation did). Many other new ranked peaks may emerge that really are unbalanced comparisons.
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Postby cftbq » Mon May 21, 2007 1:31 pm

Excellent point about the saddles, as this impacts prominence figures. So why, exactly, aren't saddle elevations being updated? At all? Surely these figures will be updated at some point, right??
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Postby Layne Bracy » Mon May 21, 2007 2:53 pm

As I understand it, nothing was remeasured. The geoid was redefined, so for any particular area, the elevation was increased by 5-10ft. A question I have is - where is the conversion listed? Besides the new 14er elevations, I don't know of any resource. Ideally, there should be somewhere to plug in coordinates, say (39N, 106W) and be told that the elevation increase is 6.8ft or whatever.

This means that anywhere a peak elevation increased, the saddle increased by almost the same amount, unless the saddle is VERY far from the summit. So, no new ranked peaks should be created just by the geoid redefinition, since it would be unlikely for a soft-ranked peak to have a distant saddle. (What's the most isolated soft-ranked peak? - probably something on the plains?) You'd need a peak with 299' prominence where the summit gained say, 6' and the saddle only 5'. A typical 280' soft-ranked peak will not get the extra 20' by the geoid change!

With the example of Drift, if the peak gained 6' then the saddle would too. Unfortunately, this creates ugly values - an interpolated summit of 13906 with an interpolated saddle of 13626.

New contour maps with the new elevations may actually require a complete resurvey if the contours are to stay at the nice 40' values. (Or is this the opportunity to jump to metric?) Or, a computer could just estimate where the new 5-10' higher contours probably fall - also unsatisfying.

Sorry to anyone who actually read this long post!
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Postby kirkmallory » Tue May 22, 2007 9:17 am

In my opinion, only saddles with listed elevations would be changed. Interpolated elevations for both saddles and summits would probably not change, since they already had a margin of error of 40 feet anyway. Interpolating is really just an estimate, a rule of thumb, and a rule we shouldn't change. I don't think we should start saying all interpolated values are half-way between the two contours plus 5 to 8 feet. So it seems to me that several summits & most saddles would remain unchanged, unless new maps show that a new contour line is added with the 5-8 extra feet. Then what do we do? Add 40 feet?

So, for a summit like Greenback Mountain, which is a soft-ranked 12er at 12,997 feet, it would become a hard-ranked thirteener if it's summit increased 5-8 feet, since it's saddle would remain at 12,700.

Rankings could change. The summits interpolated at 13,580 feet wouldn't change, but summits like Chiefs Head (currently 13,579) may become higher.
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Postby cftbq » Tue May 22, 2007 12:10 pm

Lane--don't apologize; detailed discussion is appropriate here!
Now, as I understand it, in addition to the redefinition of the geoid, there were also more accurate measurements. They are doppler radar figures generated by satellites. The old figures are all, ultimately, derived from land-based trigonometric survey values from a survey which was completed in 1929. Aircraft with stereoscopic cameras were used after that to refine intermediate values, but even those refinements still depend on the land-based benchmark figures. The radar measurements are at least capable of a higher degree of precision and, theoretically, this is built in to the results of the National Geodetic Survey (I think that's what it's called). It was actually completed in 1988, but discussions like this are only taking place now mainly because it is such a daunting project to re-do all those maps!
If it turns out that some soft/hard rankings change, then I say so be it. I doubt very seriously that theorder of elevations will change.
Also, as I understand it, while altitude values came up in Colorado, that was an accident due to our placement relative to the redefined geoid, and there may be other places where the new figures are lower than the old ones.
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Postby Layne Bracy » Tue May 22, 2007 12:35 pm

Greenback Mtn is a good example of the problem of only raising spot elevations without changing the contours. It leads to a mixed calculation of the prominence - defining the summit by the new geoid and the saddle by the old geoid.

If the change is 5', raising Greenback to 13002', then there will also be a 1/8 chance(5'/40') that the saddle gains a new contour, making its interpolated elevation 12740', giving a prominence of only 262'. So, of the peaks with prominence 295-299', 7 out of 8 will become ranked, while 1 out of 8 becomes unranked.

Of the peaks with P280-294', none could become ranked, but again 1 out of 8 would become unranked.

Now look at the error range peaks, with P300-319. There would also be a 1/8 chance of these peaks losing 35' prominence(gain of 5 for the summit minus 40 for a higher saddle), making them unranked or soft-ranked.

Surprisingly, even some ranked peaks with over 320' interpolated prominence would become soft-ranked. P335 and above are safe. But, a P334 could gain 5' and then lose 40, making it soft-ranked at P299.

Also, as mentioned, the rank order of peaks would be mixed up based on different maps. Chiefs Head goes to 13584 based on the new system but a 13580 stays as is based on the old, when it would actually have a 1/8 chance to gain 40' and become a 13620!

It is problematic to simply raise the spot elevations without knowing which interpolated saddles and summits get a new contour.
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Postby kirkmallory » Tue May 22, 2007 6:34 pm

I guess the basis for my opinion was that if the USGS ever gets around to reprinting maps, they'd most likely just simply change the numbers, but leave everything else as is. Seems to me that would be an easier project than redrawing every contour line on every map. But maybe I'm totally wrong.

But we should be careful what we wish for. If they want to completely redraw the maps based on the new geoid, they might change to metric, use 20-meter intervals (62+ feet), not list several summit elevations (like they did in CA), and create a gigantic mess for us.

So, if they simply reprinted the map that has Greenback Mtn on it, with a new elevation of 13,002, but the saddle still between 12,680 and 12,720, would we then accept it as a hard-ranked 13er? It's not like that saddle was exactly 12,700 before. Nothing changed about Greenback Mountain in reality - it has either been a ranked peak or unranked peak all along. We've only just guessed based on our limited data - a map with a margin of error of 40 feet.

Until they redraw maps, I agree that we should stick with the old elevations.
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Postby Layne Bracy » Tue May 22, 2007 7:34 pm

cftbq - I missed your post while I was composing mine. Thanks for the additional insight!

Kirk, I guess this boils down to something we've probably discussed before - the hope that one day we have precise maps redone with GPS/satellite technology. I recall from a discussion of an Alaska county highpoint that the satellites have missed summit features like thin flakes, but there's no reason to think that at some point this will be possible.

If the maps are reprinted with new spot elevations but the same contours, I guess we'll have to decide what to do. All the contour lines would then be falsely low.

Personally, I hope we do join the rest of the world with metric some day. I will admit, though, that it would be sad to see 13ers and 14ers go away. On the other hand, the goal of completing all the 4000ers leaves off Lizard Head, I believe!

This would also probably cause us to use a 100m prominence cutoff for ranked peaks, which eliminates Bross, Challenger and Thunder Pyramid from the high 100. (The first two wouldn't be missed much!)

Then there is the contour interval change, which would take getting used to. Probably 10m is too tight for the mountains, and 15m means missing 2/3 of the 100m marks, so 20m probably works best. I'm unaware of the CA situation, but that would be unfortunate if summits were omitted!
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Postby MikeRodenak » Mon Nov 19, 2007 12:25 pm

To add even more confusion... The new Traills Illustrated maps that I have purchased (updated in 2006 or 2007) now are using 50 foot contour intervals. Perhaps this was their solution to the 5-10' increase in the geoid? Now interpolating contours adds 25' to both summit and saddle so the prominence stays the same but the elevations go up 5'.

I haven't seen any new USGS quads released, but I did find it interesting that Trails Illustrated changed countour intervals.

I still use all the old elevations, just because I haven't seen a complete list yet. You know there are a few 12ers that became ranked 13ers but no one seems to care yet.

Oh and Layne you are correct, Lizard Head is NOT 4000M. The cut off for 4000M for peaks in Colorado is "Pika Peak" in the Holy Cross Wilderness. Not taking into account the geoid change of course!
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