"Sunlight Spire" LiDAR Elevation

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Salient
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Re: "Sunlight Spire" LiDAR Elevation

Post by Salient »

I wonder if LIDAR technology could be used to differentiate long time questions in mountain height around the world. Eg. Pico Cristobal Colon vs Pico Simon Bolivar, Hkakabo Razi vs Gamlang Razi or whether certain mountains that haven't been climbed or properly measured are off by a decent amount like how Ulugh Muztagh was considered 800m taller than it actually was back in the day.
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Re: "Sunlight Spire" LiDAR Elevation

Post by bdloftin77 »

Boggy B wrote: Fri Nov 05, 2021 10:02 am On 2nd look, given your 45' figure for scale, your view is probably limited to the area designated in this photo from the N.
In this case your "saddle" is the shallow notch to the left (E) of the highpoint, and the 13732.03 point is just E of that.
If that's true, it would seem LiDAR missed the highest parts of those narrow summit blocks as the area to the E was at least several feet below them.

weolusN.jpg
Your last picture matches well! I think you are correct. Below is a picture further zoomed out to match your last picture.

If the true summit is at least several feet (and not a fraction of a foot) above the 13,732.03 point, then it looks like the lidar might have been near summit area, but not the true summit.

I'd say that this summit is indeed ranked, even though lidar says it's a half foot below that threshold. From your picture, I'd agree that the small summit block area is at least a few feet higher than the flatter/larger block to the east containing its 13,732.03 high point. As for the exact summit, it would more likely be ranked if the actual summit was caught by lidar as the "13,732.45" point, instead of the actually lower "13,732.55" point 6 feet to the WSW.

Is this correct? Would you say that the true summit is in the vicinity of the "13,732.45" point right next to the drop-off to the east? How much lower do you think the rocks behind Kylie/to the west are? Since it caught a 13.732.55 point to the west which is actually lower (correct me if I'm wrong), then we can add at least X amount of feet to that point to get the true summit... = however much lower the western rocks are below the true summit, we can add that to the 13732.55 elevation to estimate the true elevation.

Below that is a screenshot of what I see for W Eolus' saddle. I labeled 5 candidates, of which I like "B" the best.
A: 13,433.67
*B: 13,433.08
C: 13,433.44
D: 13,433.01
E: 13,433.24
W Eolus Profile (left is east, right is west)
W Eolus Profile (left is east, right is west)
W Eolus Profile.png (428.35 KiB) Viewed 1385 times
West Eolus, further zoomed out
West Eolus, further zoomed out
WEolus.png (585.44 KiB) Viewed 1403 times
West Eolus Saddle
West Eolus Saddle
WEolus_Saddle.png (123.88 KiB) Viewed 1403 times
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Re: "Sunlight Spire" LiDAR Elevation

Post by bdloftin77 »

Here's the more zoomed-in screenshot again for easier reference.
W Eolus Labeled
W Eolus Labeled
WEolusLabeled.jpg (134.01 KiB) Viewed 1384 times
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Re: "Sunlight Spire" LiDAR Elevation

Post by Boggy B »

bdloftin77 wrote: Fri Nov 05, 2021 2:05 pm If the true summit is at least several feet (and not a fraction of a foot) above the 13,732.03 point, then it looks like the lidar might have been near summit area, but not the true summit.

I'd say that this summit is indeed ranked, even though lidar says it's a half foot below that threshold. From your picture, I'd agree that the small summit block area is at least a few feet higher than the flatter/larger block to the east containing its 13,732.03 high point. As for the exact summit, it would more likely be ranked if the actual summit was caught by lidar as the "13,732.45" point, instead of the actually lower "13,732.55" point 6 feet to the WSW.

Is this correct? Would you say that the true summit is in the vicinity of the "13,732.45" point right next to the drop-off to the east? How much lower do you think the rocks behind Kylie/to the west are? Since it caught a 13.732.55 point to the west which is actually lower (correct me if I'm wrong), then we can add at least X amount of feet to that point to get the true summit... = however much lower the western rocks are below the true summit, we can add that to the 13732.55 elevation to estimate the true elevation.
We should have been on the spot labeled 13732.45, as directly E of the summit block was the notch, as shown in the photo of Kylie. That makes 13732.55 the slightly lower block. From where the photo was taken on a platform E of the notch, the summit was above my head. We walked over to the E end of the 13732.03 area before descending, and I don't recall thinking it was a summit contender (certainly not within 1 foot).

My guess is neither of the summit blocks were sampled precisely (which wouldn't be a surprise considering their diameter), and that this peak is ranked. Of course I don't wish that on anyone not interested in playing with this particular blend of gravel. I'm happy to call it officially unranked until a survey with better horizontal resolution proves the contrary.

It also wouldn't be that hard to mine a foot of gravel off the top of either of those blocks.

I took a look at the 2018 bare-earth 1-meter DEMs for this area, and the biggest summit/saddle delta I found was 286'. I thought that DEM is the rasterized version of these LPCs? But there were 2 overlapping lidar and DEM files each, so maybe I grabbed the wrong one.
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Re: "Sunlight Spire" LiDAR Elevation

Post by bdloftin77 »

Boggy B wrote: Fri Nov 05, 2021 2:56 pm
bdloftin77 wrote: Fri Nov 05, 2021 2:05 pm If the true summit is at least several feet (and not a fraction of a foot) above the 13,732.03 point, then it looks like the lidar might have been near summit area, but not the true summit.

I'd say that this summit is indeed ranked, even though lidar says it's a half foot below that threshold. From your picture, I'd agree that the small summit block area is at least a few feet higher than the flatter/larger block to the east containing its 13,732.03 high point. As for the exact summit, it would more likely be ranked if the actual summit was caught by lidar as the "13,732.45" point, instead of the actually lower "13,732.55" point 6 feet to the WSW.

Is this correct? Would you say that the true summit is in the vicinity of the "13,732.45" point right next to the drop-off to the east? How much lower do you think the rocks behind Kylie/to the west are? Since it caught a 13.732.55 point to the west which is actually lower (correct me if I'm wrong), then we can add at least X amount of feet to that point to get the true summit... = however much lower the western rocks are below the true summit, we can add that to the 13732.55 elevation to estimate the true elevation.
We should have been on the spot labeled 13732.45, as directly E of the summit block was the notch, as shown in the photo of Kylie. That makes 13732.55 the slightly lower block. From where the photo was taken on a platform E of the notch, the summit was above my head. We walked over to the E end of the 13732.03 area before descending, and I don't recall thinking it was a summit contender (certainly not within 1 foot).

My guess is neither of the summit blocks were sampled precisely (which wouldn't be a surprise considering their diameter), and that this peak is ranked. Of course I don't wish that on anyone not interested in playing with this particular blend of gravel. I'm happy to call it officially unranked until a survey with better horizontal resolution proves the contrary.

It also wouldn't be that hard to mine a foot of gravel off the top of either of those blocks.

I took a look at the 2018 bare-earth 1-meter DEMs for this area, and the biggest summit/saddle delta I found was 286'. I thought that DEM is the rasterized version of these LPCs? But there were 2 overlapping lidar and DEM files each, so maybe I grabbed the wrong one.
Thanks for the helpful info! I'd agree that West Eolus is most likely ranked. John might keep it labeled as unranked based off the lidar results only, but for those who are wanting to cover their bases, keep this peak in mind! Many lidar point-clouds we've been using claim to have an average of 2 points per meter. It looks like this area might have a slightly higher concentration than that, however those points appear to not have hit the summit high point.

John's been using the lidar point-cloud (LAS/LAZ) files only, and not DEMs. Unfortunately DEMs are less accurate because they take averages of point-cloud values, flattening summits and saddles. Even worse, they sometimes miss entire summit blocks altogether because they often use the ground class only. I had to turn on both class 1 (Unclassified) and class 2 (Ground) to see Sunlight Spire's summit block, otherwise the whole spire was missing using class 2 only.

For West Eolus, I took another look using both Unclassified and Ground, and using Ground only. Below are the results. Using Ground only, the entire summit ridge is completely filtered out. This probably explains the 186' prominence value you found (I found high values of 13704-13706 near the summit ridge, but higher values than that completely west of and below the summit ridge were not filtered out (perhaps your algorithm picked those up).

Note that class 1 and 2 are checked in the first image, and only class 2 is checked in the second.

Using the ground class only is sometimes helpful though, as shown earlier in this thread with building tops and tree tops. It really depends on the situation as to whether which one is best. If you're above treeline, using both classes is often helpful, as there are more points, and you're better able to catch the summits and saddles. However, large man-made cairns/rock walls are often caught. Below treeline or near man-made structures, using class 2 (Ground) is helpful as it usually filters out these objects pretty well.
West Eolus Class 1 and 2 (Unclassified and Ground)
West Eolus Class 1 and 2 (Unclassified and Ground)
WEolus_Class1_and_2.png (406.55 KiB) Viewed 1237 times
West Eolus Class 2 Only (Ground Only)
West Eolus Class 2 Only (Ground Only)
WEolus_Class1_Ground_Only.png (238.34 KiB) Viewed 1237 times
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