Question for Mike G. -- Gold Dust Peak summit elevation?

[RyanSchilling]

Mike, I was wondering if you could shed some light on the summit elevation for Gold Dust Peak? The quad indicates a summit elevation of 13,365', whereas your book seems to be the place where the elevation of 13,382' was introduced. This can't be an interpolated value, can it?

[John Prater]

Ryan, have a look at this 14erWorld post. The appendix in G&M addresses this. The 13,365 elevation apparently applies to the eastern closed contour on Gold Dust. G&M must have concluded in the field that the western closed contour is higher. Thus, they "estimate the elevation to be midway between the printed elevation and the next higher contour." (13400+13365)/2 = 13382.5, so they use 13,382 for Gold Dust. Hopefully, Mike can confirm this when he checks in.

I am a bit curious why they didn't choose to use the extrapolated elevation for the higher summit if that extrapolated elevation is higher than the printed elevation of the lower summit. In this case, why not use the extrapolated 13,380 rather than 13,382? Maybe to use a consistent approach in the cases where this applies?

[RyanSchilling]

Thanks for the information, John! I poked around in G&M's book, but I didn't see the note you called my attention to. I think you're right about the consistency issue. The only thing I don't like about this solution is that it makes it more difficult to identify summits with interpolated elevations while perusing the list (since they're usually found in increments of 40').

BTW, I noticed your table in your FW post. Did you ever hear from Roach about the discrepancies b/w his list and G&M's?

[Mike Garratt]

Yes the west summit is higher.
The best elevation is 13380 according to the 'rules'.

It was 13380 in the 1st and 2nd edition.
Got changed in the 3rd edition when we updated the lists to replace the data from 15 minute topos with 7.5 minute topos.

Not sure how this got into the book as 13382.
Bob is the guy with the transit/level.
He climbed it between the 1st and 3rd edition.
I am sure he had some good argument at the time as to why it should be that way.
Damned if i know.

Mike

[kirkmallory]

Garratt & Martin established a modified interpolation rule for summits higher than the area with a printed elevation on the map, explained on page 182-183 of the third edition:

"Another problem is determining an exact elevation for some summits. Many writers and users of topographic maps regard the elevation of a mountain to be the figure printed on the topographic map if there is a number printed near the summit. In many cases, however, a measured elevation printed on the map is not at the high point. For example, at the top of West Needle Mountain there are three closed contours of 13,040 feet. The southwest one has a listed elevation of 13,045. We found, however, that the northeast high point is higher. In such cases, we estimate the elevation to be midway between the printed elevation and the next higher contour, thus making 13,062 feet the elevation of West Needle Mountain.

Another example is the unnamed summit between Blanca Peak and Iron Nipple. There are two closed contours of 13,080 feet. The southwest one has a listed elevation of 13,081 feet. We found that the northeast one is higher. Its interpolated elevation is 13,100 and that is listed as the elevation of this summit. Our general rule is: If an interpolated elevation of a closed contour is higher than the elevation listed on the map for another closed contour, the interpolated elevation is used unless we have first-hand knowledge from climbing the peak that the elevation is the high point. Other examples of summits higher than the printed elevation are Gold Dust Peak and Mount Flora."


So in the case of Gold Dust Peak, the listed elevation is 13,365. They determined from climbing the peak that the west summit is higher. Therefore, 13,400 (the next higher contour) minus 13,365 = 35. 35 / 2 = 17.5. Add 17.5 to 13,365 and you get 13,382.5. Obviously it's rounded down.

In the example of Mt. Flora - the southern summit is listed as 13,132. It has been determined that the unlisted northern summit is higher. The next higher contour would be 13,160, less 13,132 = 28. 28 / 2 = 14. 14 + 13,132 = 13,146 as listed in their book.

Another summit like this is Unnamed 13,463 on the Independence Pass Quad south of Red Mountain, southwest of Middle Mountain. The listed elevation is 13,447, but the contour to the south is not listed, but has been determined to be the summit. The next higher contour would be 13,480, less 13,447 = 33. 33 / 2 = 16.5. 16.5 + 13,447 = 13,463.5. Round down and you get 13,463.

In the case of UN 13,100 between Blanca & Iron Nipple, interpolating between the listed elevation (13,081) and the lowest contour (13,080) gets the same number - 13,100.

So why use this rule and not simply use an interpolated elevation using just the contours? I've wondered that myself.

But what if the listed elevation was higher than the interpolated value of the neighboring contour that has been determined to be higher? Example: What if there was a summit listed at 13,470 within a 13,440-foot closed contour. Then a second 13,440-foot closed contour next to it, without a listed elevation, was determined to be higher. It would be interpolated at 13,460 using only the contours. But interpolating between the listed elevation (13,470) and the next higher contour (13,480), it would be 13,475. It would then be listed as being higher than the 13,470 point, as it should. I'm not aware of any cases like this, but perhaps the rule has been set to establish consistency for when it does.

It's interesting to note that in Roach's 13er book, he agrees with Garratt & Martin for UN 13,463, Gold Dust, and West Needle; but uses 13,081 instead of 13,100 (a.k.a. "Huerfanito"), and lists Flora as 13,132 instead of 13,146.

[Layne Bracy]

That all makes sense. But, values like 13382 and 13146 give the false appearance of measurements that are accurate to the foot.

In these cases, interpolated elevations of 13380 and 13140 are better, in my opinion, because they do not pretend to be anything other than interpolated values.

Hopefully these discussions will become irrelevant in the future as GPS improves in accuracy and we can re-measure everything.

[John Kirk]

Long time since this was posted, but in the interest of consistency I am changing 13463 to 13460 and Gold Dust to 13380.