For those interested in the preliminaries of the NGS's third geoid slope validation survey in southern Colorado (GSVS17), here is a PowerPoint presentation given by Derek van Westrum and Pamela Fromhertz on March 7, 2018 at the PLSC conference.
The Basis of NGS' New Geopotential Datum and the Geoid Slope Validation Survey of Southern Colorado
Pamela Fromhertz also wrote a companion article in the PLSC's latest issue of Side Shots entitled, NGS Geoid Slope Validation Survey 2017 Conducted in Southern Colorado Summer of 2017
The article begins on page 17.
ETA:?ÿ The photos of the "dimple-ometer" on page 20 are intriguing.?ÿ I'm shocked that a certain someone had not brought this dimple depth gauge to market!?ÿ ??ÿ
Thanks for the links.?ÿ I wish I had known when they were working on the Iowa GSVS14 operation, only a few miles from home, so I could have seen some of the work in person.
The dimple-ometer is interesting.?ÿ The need for such a thing was mentioned in a recent thread.?ÿ You have to be careful that the meter and the rod both have either the same radius or both a small enough radius to hit the bottom.
Something I hadn't realized until recently is that they will not use the GSVS results to constrain the new geoid.?ÿ It is only for checking the accuracy of the model.
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Me too!
I am more excited about the GSV17 results than anything to come down the line in a long time.
I "suspect" that the final results will be an real "eye opener" for a lot of folks.
I wish that the NGS had the time and MONEY to run a similar survey along Interstate 80 (coast to coast), but GSV17 should answer the questions that are on many of our minds out here in the Mountain West.
Loyal
edit...whoa, what happened to Mike's post that I was replying to?
No skullduggery involved. I had some problems with my settings resulting in the display of my email address. I deleted the post to eliminate the unwanted display.
The post Loyal responded to included a link to a ??One-Pager? by NGS containing lots of details about the fundamentals.
See:?ÿ https://www.ngs.noaa.gov/GEOID/GSVS14/GSVS14SurveyOverview.pdf
I also bemoaned the fact that none of the surveys have resulted in a Final Report which might allow a better understanding of what the surveys achieved.?ÿ
Unfortunately, I no longer have free access to the Journal of Geodesy where a number of the significant findings have been presented in dense, rich, mathematical detail.?ÿ
In the most recent survey in Colorado, I had hoped to see something on the deficiencies with Helmert heights when working in high elevations.
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Mike, you posted a link not long ago to a paper that used a better definition than Helmert. Have you seen any indication that NGS will move to something like that in 2022??ÿ
Bill93, I have no insight into NGS plans. I had hoped a final report and supporting data would be made available to see how the data was analyzed.?ÿ
I do not know whether there is any discussion of the advantages of changes to the current Helmert-based orthometric heights. It seems a shame to not take advantage of the better data/equipment and understanding/theory now available.
In the real world of budgets, decisions must be made.?ÿ
The three GSVS?? provide lots of data for researchers. Let??s hope they are given unfettered access. I could see the issue of orthometric height definitions as a good M.S. topic.
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