LiDAR - US State High Points

[14erFred]

Nice work in obtaining the critical measurements required to determine the exact location of Pennsylvania's true high-point, Eric. I admire your tenacity and ingenuity in overcoming the logistical challenges involved, your ability to surmount the physical obstacles that conspired to thwart your mission, and your technical knowledge and skills regarding the geological survey work. And your succinctly written narrative report was a joy to read. Well done, sir. Well done!

[Eli Boardman]

On Monday Sept 9 I brought a dGPS (spectra promark 220 with ashtech antenna) to Mt Davis and the northern and southern candidate PA highpoints that Lidar data measured higher. I took a 5hr measurement on the boulder, 2hr measurement on the northern candidate, and 2 hr measurement on the southern candidate. I processed data with OPUS and PPP.

I found that the traditional boulder summit is still the highpoint of PA.

Traditional boulder summit: 3213.3 ft +/- 0.2 ft
Davis North: 3210.0 ft +/- 0.1 ft
Davis South: 3209.8 ft +/- 0.1 ft

(NGVD29 datum, same as quad uses)

Detailed trip report with analysis here:
https://www.countryhighpoints.com/mt-da ... nt-survey/

And this is why we can't trust the lidar "ground" classification.

Nice work Eric!

[Candace66]

I have always been under the impression that GPS isn't particularly accurate with regard to elevation. At least not as accurate as it's calculation of location in the horizontal plane. Not that it matters a lot to me as I don't pursue elevation-based lists, but the Lidar project and this debate are interesting.

I'm curious why you took a 5-hour reading in one spot, but 2 hours each at the other spots?

[climbingcue]

Nice work, happy I don’t need to revisit Pennsylvania.

[EricGilbertson]

I have always been under the impression that GPS isn't particularly accurate with regard to elevation. At least not as accurate as it's calculation of location in the horizontal plane. Not that it matters a lot to me as I don't pursue elevation-based lists, but the Lidar project and this debate are interesting.

I'm curious why you took a 5-hour reading in one spot, but 2 hours each at the other spots?

You're correct that a conventional consumer-grade GPS would not be accurate enough for this survey, and vertical errors are generally 2x-3x horizontal errors for GPS. Errors on a consumer-grade GPS can easily be 20ft vertical. I used a survey-grade differential GPS, which is different and much more accurate. This is what surveyors use, and you'll see these in use at construction sites. It has access to many more satellites, uses an external antenna to help with multipath errors and sky visibility, and records data that can be post processed to correct for atmospheric distortions using nearby base stations located around the country. I can typically get errors down to +/-0.1ft vertical with a one-hour measurment. Longer measurements yield lower error.

I took a 5 hour measurement on the boulder because that's as long as my battery lasted (I could probably tweak the sampling rate in retrospect to get that longer). The boulder has overhead tree branches with leaves that will add error so I wanted a longer measurement to reduce error. The north and south candidates were in low brush that I could clear out and get my 2m antenna rod above, so sky visibility was much better. That's why I went for a 2 hour measurement there. 2 hours is the cutoff time between 2 different processing methods on OPUS (rapid static vs static). If I'm going to do more than 2 hours and processing with OPUS I'd better go for 3+ hours to actually get improved results, and that didn't seem necessary in those conditions.

[bdloftin77]

I found that the traditional boulder summit is still the highpoint of PA.

Thanks for your hard work and attention to detail, Eric! It's much appreciated. The LiDAR class 1 returns of the summit boulder were only a few inches lower than what you measured, but the ground classification algorithm for the dense shrubs was definitely inaccurate. John updated LoJ to show the traditional boulder as the true PA high point. https://listsofjohn.com/peak/17861

Thanks for taking a look at Mt Rainier as well! The snow definitely melted a lot from the old location. Sharing your COHP email below.

"I brought a dGPS up Rainier two weeks ago and found Columbia Crest has melted down 21.8ft since the last dGPS survey in 1999. The new highpoint is on the SW crater rim, at 14,399.6ft +/-0.1ft (NGVD29 datum, same as quad uses). Location 46.851731, -121.760396. I estimate the highpoint location switched around 2014.
This affects the Pierce county, WA highpoint.

If you want to read the extensive analysis I put up a trip report here:
https://www.countryhighpoints.com/mt-ra ... on-survey/"

If you ever go to Arvon/Curwood in MI and Timms/Pearson in WI, your results will be highly anticipated! Also if you check out Black Mesa.. There are a few decent-sized, natural-looking rocks near the trees near the traditional high point that LiDAR might have not picked up (different from the big man-made cairn). In the LiDAR location, there are some shrubs, the base of which might have been misclassified by the ground point algorithm.

If you or someone you trust with the GPS ever feel adventurous, there's one 13er summit in Colorado that few people have ever climbed which might very well be ranked (summit minus saddle elevation >= 300 ft), and worthy of being added to the Colorado 13er ranked list: https://listsofjohn.com/peak/155

[bdloftin77]

For Black Mesa, the (natural-looking) rocks to the right of the tree were probably not caught by LiDAR (not to be confused with the man-made cairn in the foreground).

Traditional Summit Area

Black Mesa Traditional2.jpg (349.31 KiB) Viewed 16659 times

The LiDAR summit area ground point classification algorithm might have been influenced by the base of the trees/shrubs in the picture below. The traditional monument is on the far right.

LiDAR (Ground Points) Summit Area

Black Mesa LiDAR2.jpg (366.59 KiB) Viewed 16659 times

[KentonB]

If you ever go to Arvon/Curwood in MI and Timms/Pearson in WI, your results will be highly anticipated!

As a former Michigander, the debate between Arvon and Curwood has raged for decades (and probably longer). Both summits have a lot of trees, so I wasn't too sure how accurate LiDAR could be.

Anyway, yes, if you ever make it to Michigan to survey Arvon/Curwood, please post the results!

[12ersRule]

If you ever go to Arvon/Curwood in MI and Timms/Pearson in WI, your results will be highly anticipated!

As a former Michigander, the debate between Arvon and Curwood has raged for decades (and probably longer). Both summits have a lot of trees, so I wasn't too sure how accurate LiDAR could be.

Anyway, yes, if you ever make it to Michigan to survey Arvon/Curwood, please post the results!

I found a really good GPX for the route between Arvon/Curwood somewhere, maybe the cohp.org site or maybe loj or maybe ChrisInAZ? There was a tree in the road about 4 miles from the summit to Curwood, so I had to get out and walk/jog the rest of it, but GPX was very helpful. On the way out from Curwood though, it was a disaster. Had to turn around thanks to a pond sized puddle in the road southwest of the peak. And then another road led to nowhere.

My money is on Arvon being the highest point. Those old timey surveyors rarely ever got it wrong on something like a state HP. Just look at the PA situation, they were right all along.

[Scott P]

Those old timey surveyors rarely ever got it wrong on something like a state HP.

Utah seems to be the biggest exception. It wasn't until 1966 that Kings Peak became the known high point. Before that it was listed as South Kings Peak and before that Gilbert peak and before that Mount Emmons and before that Reids Peak.

They got it wrong at least four times and 1966 is a pretty late date for a state high point to be "discovered". I believe that it is possible that Kings Peak was the last US State Highpoint to have its first ascent. The earliest known ascent seems to be 1946 which is seven years after the first ascent of Granite Peak said by many sources to be the last US State Highpoint climbed. Before 1966 though, the wrong Kings Peak was thought to be the highpoint. A 1946 team intentionally climbed the "second highest peak in Utah" (which was actually the highest).

[HikesInGeologicTime]

Those old timey surveyors rarely ever got it wrong on something like a state HP.

Utah seems to be the biggest exception. It wasn't until 1966 that Kings Peak became the known high point. Before that it was listed as South Kings Peak and before that Gilbert peak and before that Mount Emmons and before that Reids Peak.

They got it wrong at least four times and 1966 is a pretty late date for a state high point to be "discovered". I believe that it is possible that Kings Peak was the last US State Highpoint to have its first ascent. The earliest known ascent seems to be 1946 which is seven years after the first ascent of Granite Peak said by many sources to be the last US State Highpoint climbed. Before 1966 though, the wrong Kings Peak was thought to be the highpoint. A 1946 team intentionally climbed the "second highest peak in Utah" (which was actually the highest).

Did LiDAR confirm Kings as the high point? I seem to remember that being a question that came up in one of the LiDAR threads when all the new data first came out, but I don't recall if it was ever confirmed (or deemed something that needed to be confirmed).

[madmattd]

Did LiDAR confirm Kings as the high point? I seem to remember that being a question that came up in one of the LiDAR threads when all the new data first came out, but I don't recall if it was ever confirmed (or deemed something that needed to be confirmed).

LOJ shows King's is still the highpoint, and gained ~3' from LiDAR (13528->13531). Second is South Kings Peak, picking up 6' from LiDAR to sit at 13,518'.