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base9geodesy
(@base9geodesy)
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October 22, 2018 12:49 pm  

What a great day to be a surveyor.  After two years of nagging the University of Cincinnati, this morning a small group of us were finally allowed to search for the remnants of the telescope pillar of the old latitude observatory (1899-1915).  With the use of ground penetrating radar we were quickly able to identify the most likely area and the first push of a probe we knew we had it.  It's hard to describe to non-surveyors what it feels like when you've uncovered a mark not seen in 100+ years.  The Professional Land Surveyors of Ohio will work with UC to come up with an appropriate commemorative monument and host a dedication event sometime next spring. 

DSCN0706
DSCN0720


RADAR, Jerry Hastings, Bill C and 4 people liked
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Wendell
(@wendell)
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October 22, 2018 12:53 pm  

I've always said that the treasure hunt is the most fun part of surveying. Congrats and thanks for the photos! 🙂

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SPMPLS
(@spmpls)
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October 22, 2018 1:07 pm  

I have had the pleasure of visiting the Latitude Observatory in Ukiah California with our NGS Regional Geodetic Advisor.

Observatory Park

https://www.ngs.noaa.gov/web/news/NOAA_Heritage_Asset_on_Loan.shtml

I knew there had been one in Cincinnati during the early years of the project. That is very cool that your were able to locate the remnants of the pillar and that the site will be memorialized in some way. The long term viability of the Ukiah observatory really needs to be secured so that this historical site is around for many generations to come.


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SPMPLS
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janebrowe
(@janebrowe)
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November 8, 2018 5:25 am  

Good morning!

I'm helping Underground Detective who worked on this project with you on a blog post about the project.

I'm wondering if I could quote your post above within the blog.  I'd be happy to provide a backlink to any professional site you'd like me to reference.

My email address is [email protected]  Phone number: 513-521-5129.

Thank you!


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Paul in PA
(@paul-in-pa)
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November 8, 2018 6:25 am  

Will you be comparing record latitude observations with current GNSS observations?

Paul in PA


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base9geodesy
(@base9geodesy)
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November 8, 2018 7:53 am  

While it is certainly our intention to try and perform GPS observations at the site we expect that our effort may be impacted by a rather significant tree just slightly to the southeast of the pillar.  Even if we do get good results it is always a struggle to compare a coordinate that was derived from astronomic observations with a geodetic position.  Even the best deflection of the vertical model such as DEFLEC12 is only a good approximation.  A couple of years ago I performed an analysis of 80 USC&GS astronomic stations using their published astronomic coordinates and DEFLECT12 to compute their geodetic coordinates and then comparing those stations with their published NAD 83 values - my results indicated a 2 sigma difference of 1.04" in latitude and 1.65" in longitude. 


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GeeOddMike
(@geeoddmike)
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November 8, 2018 11:39 am  

Time to break out the T3!

For those interested, here’s a link to the Manual of Geodetic Astronomy: ftp://ftp.library.noaa.gov/docs.lib/htdocs/rescue/cgs_specpubs/QB275U35no2371947.pdf

Ah, the ancient arts...

I imagine the leaves will be off before long. 

This post was modified 2 weeks ago by GeeOddMike

“To be surprised, to wonder, is to begin to understand,” - Ortega y Gasset


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GeeOddMike
(@geeoddmike)
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November 8, 2018 1:27 pm  

83D21124 DB24 4825 9829 23E3C5680560

Actually the Wild T-4. See:  https://celebrating200years.noaa.gov/theodolites/wild.html

 

“To be surprised, to wonder, is to begin to understand,” - Ortega y Gasset


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RADAR
(@dougie)
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November 8, 2018 3:13 pm  

my results indicated a 2 sigma difference of 1.04" in latitude and 1.65" in longitude. 

@base9geodesy I'm not an expert, but these numbers seem to be a lot, to me. Would you care to elaborate? 

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base9geodesy
(@base9geodesy)
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November 8, 2018 3:38 pm  

It pretty simple really.  I have collected 80 stations with NAD 83 coordinates published as part of the National Spatial Reference System that were originally established as either an astronomic latitude and/or longitude station.  There are several hundred astro stations in USC&GS Special Publication 110 "Astronomic Determinations."  Using the NGS tool DEFLEC12A it's quite simple to compute the north-south (Xi) and east-west (Eta) deflection components.  Using the standard formulas for converting an astronomic value to a geodetic value (see page XI in the Manual of Astronomy that GeeOddMike referenced) you can then get a value that you can compare with the published NAD 83 coordinates.  It's then a simple matter of subtracting one from the other and computing the average and then at the 2 sigma (95% confidence) of the set of 80 values, which for those stations I used returned the values of 1.04" in latitude and 1.65" in longitude.  I am hoping to find the time to do the same comparison but instead use the predicated IGS08 values and deflection tool in the current xGEOID18 Beta tool from NGS that will give us a closer idea of what NATRF2022 will look like.  I've done a couple already and was very impressed with the results.


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GeeOddMike
(@geeoddmike)
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November 8, 2018 10:02 pm  

Another C&GS publication of relevance is: ftp://ftp.library.noaa.gov/docs.lib/htdocs/rescue/cgs_specpubs/QB275U35no1101925.pdf

SP110, Astronomic Determinations, by Sarah Beall, from 1925

Lots of interesting history.

“To be surprised, to wonder, is to begin to understand,” - Ortega y Gasset


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Larry Scott
(@larry-scott)
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November 9, 2018 4:39 pm  

So doesn’t converting Astro to geodetic (Xi, Eta) return approximate geodetic in the original datum? Did you do a drum transformation from NAD27(?) to NAS83?

the longitude may’ve been relative to the Naval Obsebatory meridian. 

Just asking


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