Colorado LiDAR Findings

[Boggy B]

Nice work and interesting research, Jed!

The data prep sounds intensive. One of the LAS I was fiddling with had 20 million points. Using DEMs to isolate summit elevations is a clever way to tackle the challenge of huge datasets. Saddles are a sticky problem, even as you demonstrated if you're working within some radius of a known saddle location, but especially if you want to algorithmically discover saddles with no foreknowledge of the coordinates--to this end DEMs are much easier and faster to process, but at some point you have to perform a computationally expensive search on the raw data to isolate which point it is, which in highly rugged terrain is subject to errors in the method used to determine whether two given points in an LPC are actually adjacent.

Am I reading correctly that you promoted El Diente to ranked status?

[Teresa Gergen]

Boggy B, I independently analyzed El Diente today, then brought in the lidar lat/long that is currently on the LOJ page to compare my results, and found that I had chosen the exact same lidar points as the summit and saddle that were selected for LOJ (thus the same elevations and resulting prominence).

Jed, would you be interested in doing a manual lidar analysis of El Diente and letting us know how it compares with your automated results?

[Boggy B]

I'm guessing it was a typo. His study summit/saddle elevation tables mostly align with LoJ (saddle -2 feet). Too bad..

[Teresa Gergen]

Jed's El Diente study summit elevation, Table 2, page 27 of the .pdf file: 14175.
Jed's El Diente study saddle elevation, Table 6, page 30 of the .pdf file: 13909.
Jed's study prominence for El Diente: 14175 - 13909 = 266, unranked.
Jed included El Diente in Table 9, .pdf page 33, of peaks promoted from unranked to ranked, with a listed prominence of 335.

I didn't notice this until Boggy B brought up the possibility of a typo.

[geojed]

Jed's El Diente study summit elevation, Table 2, page 27 of the .pdf file: 14175.
Jed's El Diente study saddle elevation, Table 6, page 30 of the .pdf file: 13909.
Jed's study prominence for El Diente: 14175 - 13909 = 266, unranked.
Jed included El Diente in Table 9, .pdf page 33, of peaks promoted from unranked to ranked, with a listed prominence of 335.

I didn't notice this until Boggy B brought up the possibility of a typo.

Oops! Yes, it was an inconsistency on saddle points used when I calculated new prominences. Thank you for catching that.

As I stated in the first sentence of my discussion on my Saddle Point method (PDF pg 37):
"Saddle points are a more difficult attribute to measure and their determination did not
turn out to be quite as clean. That was why they were a secondary objective of this study."

In Figure 13 (see attached image below), I gave an example of a common error for my saddle point method. This example is actually for El Diente! When I saw that my method calculated El Diente as being ranked, I investigated it because I knew LOJ had determined that it was still unranked. So, the value of 13,909' I gave in Table 6 was actually found manually when I investigated this erroneously low saddle point. When I calculated Table 9 though, Unranked Ranked Peaks, I used the erroneously low saddle point that my automated method had determined (the red triangle in Fig 13 below), and not the 13,909' that I measured manually from my DEM at the LOJ saddle point.

My apologies for the inconsistency leading to confusion. My saddle points definitely need to be taken with a grain of salt and QC'd before using.

[lukePlumley]

Looks like another round of new Ranked CO LIDAR peaks! Keep them coming John & CO!!

[bdloftin77]

Yep! All of Colorado now has coverage via either TNM or OIT.

Some notable findings by John:

Steamboat Rock (unclimbed 5.xer) is ranked. https://listsofjohn.com/peak/6464

Clark (https://listsofjohn.com/peak/865) is 11' higher than Richthofen (https://listsofjohn.com/peak/877), and is therefore the uncontested HP of Jackson county.

Nokhu Crags (https://listsofjohn.com/peak/1307) is indeed higher than Nokhu Crags South (https://listsofjohn.com/peak/212566) by 5'.

Signal Butte (https://listsofjohn.com/peak/6280), asked about previously, remains at 299' of prominence and is now soft-ranked.

Currently peaks are ranked if they have >=299.5' of prominence (rounding up; lidar possibly missing the true HP and true saddle). The lidar soft-ranked window is 1 foot lower than this: 298.5 to 299.4999' of prominence. For quality 2 data, the lidar error of any particular point is X+- ~8 inches (+-19.6 cm; 95% confidence interval). Since both the summit and the saddle might have this error, 1.5' seems like a logical lower bound for the soft-ranked status to catch more than 95% of the maximum summit + saddle errors.

[cougar]

Great work on analyzing this latest batch.

Looks like at least one newly ranked 11er (glad I got it)

https://listsofjohn.com/peak/2254

I didn't see anything newly ranked in RMNP this round. Soft ranked 12er Baker mtn is 277 ft prominence.

[JoeGrim]

Just wanted to let you all know about a couple NoCo ranked peaks that I recently found to be more than a mile away from where topo maps indicated they should be.

The first is former ranked peak 6227; there is a point on the ridgeline a little over a mile north that is 9 ft higher (newly-discovered ranked peak 6238). John Kirk has kept the previously-presumed summit on LoJ and created a new summit.

The second peak that loses its ranked status to another nearby peak is "10833", which it turns out is 5 ft lower than Shipman Mountain (not 5 ft higher, as topo maps indicate.) So, Shipman moves up to ranked, while 10833 is no longer ranked.

One final interesting summit find is that Chimney Rock is 133 ft taller than what topo maps indicate (though remains unranked.) Spires like Chimney Rock are the most likely candidates to have a considerable change in their elevation when using LiDAR data.

[bdloftin77]

Good finds! Bummer that Chimney isn't ranked, that's a big elevation error.

The highest 200 CO peaks are now analyzed as well.

[CheapCigarMan]

The highest 200 CO peaks are now analyzed as well.

For those of us that are LoJ illiterate is there a link that provides CO’s Bi-Cents, all 200, ranked in order?

[Jon Frohlich]

The highest 200 CO peaks are now analyzed as well.

For those of us that are LoJ illiterate is there a link that provides CO’s Bi-Cents, all 200, ranked in order?

https://listsofjohn.com/PeakStats/selec ... n=200&s=CO