*PSA* - Ranked Lists Changing based off LiDAR Analysis

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Scott P
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Re: *PSA* - Ranked Lists Changing based off LiDAR Analysis

Post by Scott P »

bdloftin77 wrote: Tue Oct 26, 2021 4:46 pm+ Was Sunlight Spire surveyed correctly in the first place? Is it higher or lower than we think it is?
It is worth mentioning that the elevation is only a telemetery elevation rather than a spot elevation.
+ How high is Mt Powell A?
LoJ and most other lists use the 7.5 minute maps and they are typically the most up to date, but as a cost saving measure a lot of spot elevations were eliminated. Several of the Gores lost their spot elevations. Some older maps and sources, for example, have a spot elevation of 13,432 feet for Eagles Nest, but it is not on the latest 7.5 minute maps, though it does correlate with the elevation range of contours of 13,400-13,440 from the 7.5 minute maps. Interesting, all maps that I'm aware of that give Mt. Powell give a spot elevation list it as13,534 which does not correlate with the 7.5 minute maps.
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Re: *PSA* - Ranked Lists Changing based off LiDAR Analysis

Post by DArcyS »

jkirk wrote: Tue Oct 26, 2021 11:45 am
DArcyS wrote: Mon Oct 25, 2021 2:42 pm
bdloftin77 wrote: Mon Oct 25, 2021 11:14 am I can say with certainty that no one has completed the 12ers in Colorado. [quoting John Kirk]
The correct statement is "I can say with certainty that no one has completed the 12ers in Colorado according to a new criterion for establishing what constitutes a ranked peak."

There is no "certainty," just different ways of obtaining elevation data (i.e., more accurate means through time) and interpreting elevation data (i.e., the subjective 300' rule), where the elevation data of geologic features changes as a function of time (i.e., erosion and rising sea levels).

To each their own.
I have to disagree. LiDAR has revealed that contours are missing from the map in this case, and in fact the unclimbed peak has over 450' of prominence. There is no new criterion here, if a peak possesses more than 300' of prominence, it possesses more than 300' of prominence.
Yup, I was wrong regarding this peak, my apologies, John.

Although my point about the uncertainty about the manner of ranking peaks is still germane.

Within probability and statistics, there's a fundamental concept that the more data points, the better. Currently, determining whether a peak is ranked is based upon two points, the saddle elevation and the summit elevation. As is quite evident, there's a large degree of uncertainty and error involved in determining elevations. Based upon the LOJ LiDAR chart, I can see elevations are being determined to within a foot, but what is the error associated with those calculations? I've wandered about the hills a little in my life, and I've seen boulders that stand many feet above the surrounding ground, so how does a stray boulder just laying around on the saddle affect the confidence in a LiDAR calculation?

John initially called the soft ranked peaks the "elephant in the room," which is indicative of the uncertainty of using two points to determine whether or not a peak is ranked. The statistically better way to determine whether a peak is ranked is to count the number of contour lines "crossed" from the saddle to the summit, as contour lines are created from a multitude of points (eh, I'll avoid the hyperbole that mathematically there's an infinite number of points in a line).

Generally, 300' is used as the ranking criterion, which is most closely associated with crossing eight contour lines (at least 280') or nine contour lines (at least 320'). This gets away from the 300', but as Roach stated in at least one of his books, there's nothing magical about 300. (However, I've bowled a 300 game, so I'll assert that there's something quite magical about 300 at a bowling alley -- ha, ha sorry about the brag.)

I can make the case that 10 contour lines would make a good criterion. Ten is a round number and ten lines (at least 360') corresponds to the contour line scheme on the 7.5' topographic maps (i.e., one bold line and four fine lines every 200' on the map). Applying this to the 14ers, three 14ers are lost: Challenger, Bross, and Ellingwood. Or maybe go with 400' and 11 contour lines.

Given the lists are going through a transformation, at this point maybe some thought should be given to now using contour lines for the ranked peak criterion. Perhaps this might alleviate the burden of obtaining point elevations via LiDAR. In this day and age of computers, maybe you have multiple lists, e.g., the historic USGS list, the LiDAR list, the 8 contour line list, etc., noting that when it's all said and done, selecting the ranking criterion is quite subjective.
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Re: *PSA* - Ranked Lists Changing based off LiDAR Analysis

Post by aholle88 »

bergsteigen wrote: Tue Oct 26, 2021 1:58 pm Top of my list for demoted peaks is Bartlett. Please please! I know it will happen eventually.
Surprises me to hear you say that considering how quality a ski it is! Figure chances of getting caught or blown up are pretty slim in the spring when it’s caked in white.
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Re: *PSA* - Ranked Lists Changing based off LiDAR Analysis

Post by bdloftin77 »

Furthermore wrote: Tue Oct 26, 2021 7:04 pm
Chicago Transplant wrote: Tue Oct 26, 2021 4:12 pm + Are High Dune, 8860, and Star Dune ranked?
Having done a recent GIS LIDAR project for something in the vicinity, I can confirm that High Dune is indeed ranked. I would have to spend some time but it would be easy for me to figure out 8860 and Star. (Matching of LIDAR tiles, easy but time consuming with my limited GIS skills)

EDIT: It should be noted that High Dune was ranked the day of the LIDAR flight (2014) and could currently be in a different position, have a different saddle, and/or summit elevation.
Thanks, good to know!
Scott P wrote: Tue Oct 26, 2021 9:56 pm
bdloftin77 wrote: Tue Oct 26, 2021 4:46 pm+ Was Sunlight Spire surveyed correctly in the first place? Is it higher or lower than we think it is?
It is worth mentioning that the elevation is only a telemetery elevation rather than a spot elevation.
+ How high is Mt Powell A?
LoJ and most other lists use the 7.5 minute maps and they are typically the most up to date, but as a cost saving measure a lot of spot elevations were eliminated. Several of the Gores lost their spot elevations. Some older maps and sources, for example, have a spot elevation of 13,432 feet for Eagles Nest, but it is not on the latest 7.5 minute maps, though it does correlate with the elevation range of contours of 13,400-13,440 from the 7.5 minute maps. Interesting, all maps that I'm aware of that give Mt. Powell give a spot elevation list it as13,534 which does not correlate with the 7.5 minute maps.
I was wondering how they got survey equipment up there. So they basically triangulated where it was relative to the peak they were on, and that's how they came up with that number? So Sunlight Spire's elevation is much more of an estimation than we'd think, it sounds like. Is there a way to tell what's a spot elevation on the map, and what's a triangulation/telemetry one?

Didn't know that about Powell and other peaks! That's sad that a bunch were eliminated to save costs. Though interesting that the spot elevation that was given for Powell doesn't match with the 7.5' maps.
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Re: *PSA* - Ranked Lists Changing based off LiDAR Analysis

Post by bdloftin77 »

Anima wrote: Tue Oct 26, 2021 7:14 pm Through some quick googling, I found that LiDAR Data can be found here:

https://prd-tnm.s3.amazonaws.com/LidarE ... dex.html#/
The other website with a lot of LiDAR for Colorado is ColoradoHazardMapping.com. There's an FTP link where you can download data from around half the 64 counties. For the rest that show up on the coverage map, but not in the FTP site, you can fill out a LiDAR request form and hopefully receive the other data from them. The county LAS files from the FTP site are pretty big and take a while to download. Haven't tried out the request form yet.

The map has current and planned coverage - some areas aren't available for download on the FTP site (at least I haven't found them). The missing areas either might be planned only, or the request form might be able to access them.

Coverage Map: https://coloradohazardmapping.com/lidar
Request form: https://docs.google.com/forms/d/e/1FAIp ... Q/viewform
FTP site: https://gisftp.colorado.gov/#/State%20D ... /Counties/
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Re: *PSA* - Ranked Lists Changing based off LiDAR Analysis

Post by Boggy B »

DArcyS wrote: Wed Oct 27, 2021 2:09 am John initially called the soft ranked peaks the "elephant in the room," which is indicative of the uncertainty of using two points to determine whether or not a peak is ranked. The statistically better way to determine whether a peak is ranked is to count the number of contour lines "crossed" from the saddle to the summit, as contour lines are created from a multitude of points (eh, I'll avoid the hyperbole that mathematically there's an infinite number of points in a line).

[...]

Given the lists are going through a transformation, at this point maybe some thought should be given to now using contour lines for the ranked peak criterion. Perhaps this might alleviate the burden of obtaining point elevations via LiDAR. In this day and age of computers, maybe you have multiple lists, e.g., the historic USGS list, the LiDAR list, the 8 contour line list, etc., noting that when it's all said and done, selecting the ranking criterion is quite subjective.
I believe the elephant is the fact that, in lieu of better data, we've been using the low-res contours to guess whether peaks on the threshold are ranked.
Relative to each other, the LiDAR point elevations for saddle and summit are highly accurate and yield a much greater degree of confidence in the calculated delta. And, the ranking criterion isn't subjective--it's 300 feet.

If the horizontal resolution of this new data is 1 meter, then prominences calculated from it probably won't be subject to much revision in the future. I can think of few peaks over 13k where the highest point on the summit or deepest notch in the saddle could potentially not be sampled at that resolution. Needle Ridge, probably. Maybe Gray Needle, The Index, and Little Finger. None of which appear to be in much danger of becoming ranked, though I'm eager to see more results from the Needles. There are towers in there with easily 150'-200' of prominence that barely register on the topos. The contours on the Jagged massif W of the summit are notably bonkers.
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Re: *PSA* - Ranked Lists Changing based off LiDAR Analysis

Post by bdloftin77 »

DArcyS wrote: Wed Oct 27, 2021 2:09 am John initially called the soft ranked peaks the "elephant in the room," which is indicative of the uncertainty of using two points to determine whether or not a peak is ranked. The statistically better way to determine whether a peak is ranked is to count the number of contour lines "crossed" from the saddle to the summit, as contour lines are created from a multitude of points (eh, I'll avoid the hyperbole that mathematically there's an infinite number of points in a line).

[...]

Given the lists are going through a transformation, at this point maybe some thought should be given to now using contour lines for the ranked peak criterion. Perhaps this might alleviate the burden of obtaining point elevations via LiDAR. In this day and age of computers, maybe you have multiple lists, e.g., the historic USGS list, the LiDAR list, the 8 contour line list, etc., noting that when it's all said and done, selecting the ranking criterion is quite subjective.
Kirk's algorithm takes into account all the LiDAR points near the saddle in both the nearby valleys and both ridges and calculates the lowest point on the ridge. He cross-checks this with the interpolated saddle, double-checking everything if the LiDAR saddle is fairly different. He's also making sure the LiDAR classes are filtered such that any trees and man-made structures are not picked up. Trust me - he's being very thorough, and using more than "just one LiDAR point." Looking through the metadata for a few counties from the CO Hazard Map website, the vertical accuracy of the LiDAR is ~0.24 ft. I'd much rather use cutting-edge data like this than counting contours for ranked peaks (in some areas, many contours are wildly inaccurate, especially in very rough terrain). I'm all for refining versus scrapping the current 300' system. If you'd like to do your own work and create contour-counting lists of your own, that's great! Yes, it'll take some time. But these results will be extremely accurate.
Last edited by bdloftin77 on Wed Oct 27, 2021 1:53 pm, edited 2 times in total.
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Re: *PSA* - Ranked Lists Changing based off LiDAR Analysis

Post by Scott P »

bdloftin77 wrote: Wed Oct 27, 2021 7:15 amI was wondering how they got survey equipment up there. So they basically triangulated where it was relative to the peak they were on, and that's how they came up with that number?
Even less than that. It was calculated estimated after the survey was done rather than shot as a specific point (see below).
So Sunlight Spire's elevation is much more of an estimation than we'd think, it sounds like.
Yes.
Is there a way to tell what's a spot elevation on the map, and what's a triangulation/telemetry one?
Yes.
Elbert.JPG
Elbert.JPG (115.28 KiB) Viewed 2432 times
Some newer maps use a slighty different notation, by using an "x" and a "T" for telemetry. If there is an "x" and a "T" it means it was a spot elevation determined by telemetry only and is equivalent to the elevation without an x in the map above.
Last edited by Scott P on Wed Oct 27, 2021 1:23 pm, edited 1 time in total.
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Re: *PSA* - Ranked Lists Changing based off LiDAR Analysis

Post by CheapCigarMan »

I would think that there wouldn't be much difference between Survey Point Benchmark and Spot Elevation Shot from the Survey Point-Benchmark (especially if there was a clear line of site to the highpoint).

I would also think they would be the most accurate measurements. While the Estimated Elevation based on Telemetry would be highly variable.
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Re: *PSA* - Ranked Lists Changing based off LiDAR Analysis

Post by ekalina »

Can you say more about what the process of estimating elevation from telemetry involves? Telemetry means use of GPS, right? Does it mean someone walked a GPS receiver up to the summit and read off the elevation?
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Re: *PSA* - Ranked Lists Changing based off LiDAR Analysis

Post by Scott P »

ekalina wrote: Wed Oct 27, 2021 1:46 pm Telemetry means use of GPS, right? Does it mean someone walked a GPS receiver up to the summit and read off the elevation?
No to both. It means it was done by photogrammetric methods when they drew in the contours in from aerial photographs. Most telemetry elevations on the quads predate GPS.
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Re: *PSA* - Ranked Lists Changing based off LiDAR Analysis

Post by CheapCigarMan »

Scott P wrote: Wed Oct 27, 2021 2:18 pm
ekalina wrote: Wed Oct 27, 2021 1:46 pm Telemetry means use of GPS, right? Does it mean someone walked a GPS receiver up to the summit and read off the elevation?
No to both. It means it was done by photogrammetric methods when they drew in the contours in from aerial photographs. Most telemetry elevations on the quads predate GPS.
That's interesting piece of history.
What's the history of testing that method? What works have been done to verify that data and what were the results?
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