Quad surface area

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Quad surface area

Postby TWorth » Tue Sep 13, 2011 10:48 am

Worked this up months ago, never posted it.

Which USGS quads in Colorado have the greatest surface area? In other words, if you took all the mountainous terrain in a given quad and flattened it out until it's a plane, how many square feet/meters/miles would it contain compared to its original geographic area?

Rank,Quad,SA Ratio

SA Ratio=ratio of surface area to geographic area
*West of I-25 only*

Top 10:

1 Vail East 1.133649
2 Grouse Mountain 1.126781
3 McHenrys Peak 1.125496
4 Isolation Peak 1.125257
5 Mount Powell 1.119894
6 Hayden Peak 1.113013
7 Crestone Peak 1.108145
8 Trail Ridge 1.108045
9 Mount Big Chief 1.106854
10 Monarch Lake 1.104552

Bottom 5( All San Luis Valley):

1076 Alamosa West 1.000018
1077 Hooper East 1.000012
1078 Hooper SE 1.000012
1079 Center South 1.00001
1080 Hooper West 1.000006

Whole list:

http://ned-files.com/listq3.cgi?st=co&list=8

Surprise: No San Juan quads in the top 10. Highest is Snowdon Peak at #25

Quad with the lowest average elevation in the top 50 is Eldorado Springs(#47).

This was done using digital data and many trig calculations(~500,000 per quad).

Is there practical use of this information? Not really, other than expanding ones knowledge.
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Re: Quad surface area

Postby RyanSchilling » Wed Sep 14, 2011 9:12 am

That's really interesting, Tim. Grouse Mountain quad sticks out to me because, unlike others in the top 10, it has neither a lot of peaks (it only has five ranked peaks) nor the numerous, serrated ridges of the Powell or Hayden quads.
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Re: Quad surface area

Postby MikeRodenak » Wed Sep 14, 2011 12:12 pm

Interesting stuff indeed, I agree with Ryan, Grouse is a surprise. Especially seeing as the Mt Jackson quad immediately to the south has almost 5 times as many peaks and plenty of rough ridges!

There is a lot of vertical relief in the Grouse Mtn quad, however, the quad starts in the valley at nearly 7500' and over 13k as it starts to creep up the northern ridges of Jackson and Finnegan. That must be a big factor in why it has so much more surface area than Mt Jackson. Vail East is like that as well, it includes parts of the town of Vail before climbing back up to over 11k south of I-70. I think deep valleys must be a strong influence on the stats.
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Re: Quad surface area

Postby JoeGrim » Wed Sep 14, 2011 1:28 pm

Interesting information, Tim. How does this equate to average slope steepness for the entire quads? I'm trying to think of some way to obtain average slope from this information, but haven't figured it out yet.
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Re: Quad surface area

Postby TWorth » Thu Sep 15, 2011 8:17 am

Thanks for the comments guys. I'm always looking for new angles with this DEM stuff, gets my mind off sore muscles on those long hikes back to the trailhead.

Grouse seemed out of place to me as well.....so I even ran it again and got the same results. Digital data errors are always a possibility. It does seem a large elevation span is a big factor vs just a lot of rugged ridges or lots of summits. Looking at all those San Juan quads, Snowdon Peak seems to have the most SA due to the Animas River valley.

Joe, The surface area figure came from the average of thousands of hypotenuses which reflect elevation change from one individual DEM square and its adjascent squares. So like for Vail East the 1.13 can also be looked at as the z value of a triangle representing the overall average, where x is set to 1. So slope being y/x, and with x at 1, just find y and that's average slope. So(doing some quick trig) for Vail East average slope ends up being .532. At the low end, Hooper West ends up having an average slope of .00346. This is just an estimate, better resolution data would improve accuracy and there are more sophiticated methods to get surface area, but the quad by quad comparisons probably wouldn't change much.
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