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Lidar elevations - Candace66 - 2021-12-16
(Scroll to the bottom to see precisely why I posted this on a DV forum!)
The project to gather accurate elevations via Lidar recently came to my attention because a few individuals are analyzing data to determine accurate summit and peak elevations in Colorado.
What is Lidar data?
Added: Detailed explanation of how the data is analyzed
This is important to peakbaggers, because the results will affect elevation-based lists. For some peaks, either the summit elevation is changing, the summit may turn out to be a different high point than thought, or the peak's status as ranked/unranked is changing.
For the uninitiated, "ranked" means there is at least 300 feet of rise from the highest saddle to the summit. This is an arbitrary number chosen so that every little high point on a ridge doesn't end up being considered a summit. When people set out to complete lists such as the "Centennial Peaks" (the 100 highest peaks in Colorado), typically that means they want to climb the 100 highest ranked peaks in the state.
By the time all this analysis is done, people who thought they had completed a certain list will find the goal post moved!
The Centennial list has changed, as some peaks were dropped and some added. And the same is true for other peaks lists.Here are a couple of discussion threads on 14ers.com, a site dedicated to higher peaks in Colorado. They'll give you an idea how the analysis is being done, what they're finding, and what the results are.
Colorado Lidar Findings discussion
Challenger Peak is not ranked!
North Maroon Peak is ranked!
How this relates to DV: I'm not sure who will do a detailed analysis of the data regarding peaks in DVNP. But I would think someone would be interested in figuring out where the low point of the valley is! So far, people who wish to visit that point simply go to the -282' spot elevation on the USGS topo map. Which may or may not be the true low spot OR the correct elevation. Hopefully we'll get an exact location soon.
RE: Lidar elevations - Sparky of SoCal - 2021-12-17
(2021-12-16, 07:46 PM)Candace66 Wrote: (Scroll to the bottom to see precisely why I posted this on a DV forum!)Very interesting none the less. The folks using the old school methods for decades were still pretty close, that is another story.
The project to gather accurate elevations via Lidar recently came to my attention because a few individuals are analyzing data to determine accurate summit and peak elevations in Colorado.
What is Lidar data?
This is important to peakbaggers, because the results will affect elevation-based lists. For some peaks, either the summit elevation is changing, the summit may turn out to be a different high point than thought, or the peak's status as ranked/unranked is changing.
For the uninitiated, "ranked" means there is at least 300 feet of rise from the highest saddle to the summit. This is an arbitrary number chosen so that every little high point on a ridge doesn't end up being considered a summit. When people set out to complete lists such as the "Centennial Peaks" (the 100 highest peaks in Colorado), typically that means they want to climb the 100 highest ranked peaks in the state.
By the time all this analysis is done, people who thought they had completed a certain list will find the goal post moved!
Here are a couple of discussion threads on 14ers.com, a site dedicated to higher peaks in Colorado. They'll give you an idea how the analysis is being done, what they're finding, and what the results are.
Colorado Lidar Findings discussion
Challenger Peak is not ranked!
North Maroon Peak is ranked!
How this relates to DV: I'm not sure who will do a detailed analysis of the data regarding peaks in DVNP. But I would think someone would be interested in figuring out where the low point of the valley is! So far, people who wish to visit that point simply go to the -282' spot elevation on the USGS topo map. Which may or may not be the true low spot OR the correct elevation. Hopefully we'll get an exact location soon.
RE: Lidar elevations - trailhound - 2021-12-17
Since the low point is on the salt flat, I wonder how stable it is. I would not be surprised to find out that both the location and the elevation change with wet conditions.
RE: Lidar elevations - DAW89446 - 2021-12-17
During the course of research for my various historical writing endeavors, I’ve seen the elevations posted for Death Valley, Telescope Peak and Mount Whitney vary widely over the decades of the eastern Sierra Nevada newspapers, especially before 1900.
Early news accounts give Death Valley’s elevations less than -100 feet to more than -300 feet. Mount Whitney has been reported to be more than 15,000 feet. As well, it was common for the peak to be reported to be 14,494 and 14,495 simultaneously in the same time period.
I haven’t followed up on it, but in the mid 2000s, when I was still living in Big Pine, I remember a newspaper article stating that there was some evidence that White Mountain Peak (14,252’) was higher than Mount Whitney, as measured with new technology. But they left it open ended, as in no actual claim. I checked with my contacts at both Inyo National Forest and the White Mountain Research stations in Bishop and I got no answers. No denials, no confirmations. I got the impression that they were purposely being mum about it.
I am sure no one wanted to come out publicly if true, as that would definitely hurt the Lone Pine economy as well as the potential to impact traffic over the Pacific Crest Trail.
RE: Lidar elevations - DVexile - 2021-12-17
There’s been plenty of conspiracy theories about Whitney compared to White not to mention peaks in CO. The reality is the altitude difference between Whitney and White is so large that even a cellphone GPS can show you Whitney is clearly taller. Whitney’s official altitude has changed slightly over the years but this mostly has not had anything to do with surveys of Whitney changing but instead with the sea level datum changing due to improved models of mean sea level and the geoid. So in those small changes to the datum White’s elevation has changed right along with Whitney’s.
Candance’s point is much more interesting with peaks crossing the threshold from ranked to unranked since these are often minor peaks likely not super well surveyed and small changes crossing the 300 for threshold for ranking.
RE: Lidar elevations - GowerGulch42 - 2021-12-18
I've tried using available lidar data to pinpoint the low point, but the relative noise inherent in the data collection method means that it isn't quite accurate enough at the publicly-available level. That's not saying that it's being obscured, rather that it would require analysis and know-how (software) that I don't have or know how to use.
Lidar itself does not give accurate data on elevation right off the bat. In fact it can vary noticeably from known, established benchmarks because of the resolution of the reflection points and the aerial-acquisition method has inherent noise. Your elevation model is only as good as your ground-control points and your calibration/calculation of the data.
Re: the stability of the low point… it is known to move around quite a bit. I don't know how much it changes on a year-to-year basis, but you could figure it out by flying new LIDAR. If it were acquired from a UAS ("drone") or ground-based system then you could absolutely get the accuracy and precision needed for that analysis. That'd be a huge - and largely unsatisfying - undertaking.
RE: Lidar elevations - Candace66 - 2021-12-18
(2021-12-17, 04:32 PM)DAW89446 Wrote: I haven’t followed up on it, but in the mid 2000s, when I was still living in Big Pine, I remember a newspaper article stating that there was some evidence that White Mountain Peak (14,252’) was higher than Mount Whitney, as measured with new technology. But they left it open ended, as in no actual claim. I checked with my contacts at both Inyo National Forest and the White Mountain Research stations in Bishop and I got no answers. No denials, no confirmations. I got the impression that they were purposely being mum about it.
I am sure no one wanted to come out publicly if true, as that would definitely hurt the Lone Pine economy as well as the potential to impact traffic over the Pacific Crest Trail.
One can get a reasonably close elevation reading with a consumer GPS. Certainly better than 250 feet of accuracy. If White Mt Peak were higher, we'd know it by now, given the amount of traffic on both.
I personally didn't check the elevation when I was on either. But I didn't carry a GPS on either since they're trail/road hikes.
Anyway, why would the USFS care if a few less people came to Lone Pine, LOL. Even if Whitney were lower, it would still be a popular climb as it's a class one 14er that can be reasonably done as a day hike. The PCT is a "bucket list" attraction in itself, regardless of Whitney.
RE: Lidar elevations - Candace66 - 2021-12-18
(2021-12-18, 01:38 AM)GowerGulch42 Wrote: Lidar itself does not give accurate data on elevation right off the bat. In fact it can vary noticeably from known, established benchmarks because of the resolution of the reflection points and the aerial-acquisition method has inherent noise. Your elevation model is only as good as your ground-control points and your calibration/calculation of the data.
At the USGS link I posted earlier, Lidar is described as "...a technology used to create high-resolution models of ground elevation with a vertical accuracy of 10 centimeters."
I haven't attempted to understand step-by-step how John Kirk, BD Loftin, and others are processing and analyzing. They've explained their methods in the 14ers.com threads I posted. They're confident of their findings. And the elevations, rises, and lists on the peakbagging sites will be updated with their results.
With regard to "known, established benchmarks", they were subject to surveying and mapping errors. Not to mention, vertical datums changing over the years. Or, maybe I misunderstood what you meant by benchmarks?
There are some notable errors on the USGS topo maps where one or more contour lines are missing. A great example is the Coxcomb Mountains range in California. There are three high points in close proximity. And the 7.5' map shows the lowest of them as being the highest!
Coxcombs brief analysis
My Coxcombs trip report with map
RE: Lidar elevations - MojaveGeek - 2021-12-23
In addition to getting more accurate readings with the Lidar data, another aspect of the new analyses of elevation data includes a better measure of "sea level". The current assumption is that sea level would simply follow the general curve (geoid?) trend of the surface of the earth. But gravity is not uniform across the surface, and where there is higher gravity, sea level would actually be lower (or could be the opposite if lower gravity) across the continental interior.
I find this all interesting, but I'm not trying to complete the Colorado 14ers or hit all highpoints (by XXX measure) so doesn't matter much to me.
And as for White Mtn, my understanding is that Mt. Elbert in CO is second to Whitney?
RE: Lidar elevations - DeathValleyDazed - 2021-12-23
(2021-12-23, 05:00 PM)MojaveGeek Wrote: And as for White Mtn, my understanding is that Mt. Elbert in CO is second to Whitney?As a funny aside to Mt Whitney and Mt Elbert about ten years ago while showering at The Furnace Creek pool I enjoyed a lively discussion with four young buck climbers from Colorado who feigned (or who knows, maybe they were serious) about "having to drive all the way to California to climb the highest peak in the lower 48 after they had summited most of the tallest which happen to be in their beloved Colorado. It was all in good fun.