Jump to content
Sign in to follow this  
Followers 0
GrizzFlyer

True Meridian in Ohio

Recommended Posts

Yesterday I headed over to the Mansfield Ohio area to do a little benchmarking, but wanted to stop by a cemetery in Bucyrus to check out a geocache that used a True Meridian marker as a starting point. The geocache page has a photo of the marker. It brings to mind a couple of questions.

 

What actually is a True Meridian? It is dated 1884, so it seems to be much younger than any of the Ohio meridians mentioned in this list. I read somewhere that meridians were established in pairs, should there be another one to look for in the area? And whats in that locked box at the top? The plate with the lock on it is just a plate covering another metal piece that may be the front of a metal box. Dumb question, but who would have the key? I'll take a WAG and say its probably the County Engineer, who is the official surveyor for each county in Ohio.

 

It is not listed in the NGS database, so no PID.

Share this post


Link to post

Boundary surveys in the U.S. were determined by the use of a compass, which gives magnetic bearings (directions). Surveyors understand that magnetic declination changes from place-to-place and over time. In order to correct magnetic bearings to "true" bearings it is necessary to perform a geodetic observation, typically an astronomic azimuth, to determine the difference, called the magnetic declination, at some location. Until the development of an easily accessible national geodetic network, which didn't happen until after 1900 in Ohio, C&GS and others would establish these meridian stations where the differences were well defined so local surveyors could compare their compass to determine the local magnetic declination. In most, but not all cases these sites would consist of two markers, spaced a couple of hundred feet apart that served much the same function as a triangulation station and it's azimuth mark. Regrettably, many of these markers were never tied into the national geodetic networks and are a forgotten part of our surveying history.

Share this post


Link to post

We looked at the photo announcing Robespierre's find of this cache. A fabulous object! We suppose your guess about who has the key is as good as ours, but if we were in that area we would be all over the phone trying to find out. It's tempting to think that occasional checks of the azimuth have been made and then recorded for placement in the box. (This is assuming that the other mark is still extant somewhere within a few hundred feet.)

 

There are two sets of meridian markers on Nantucket Island, one in town and one out on the south side of the island. We'll be back in a little while with more info about them; getting it together right now might take long enough to time us out.

Share this post


Link to post

More on the Nantucket meridian markers.

 

The older set is a pair, surveyed and placed in 1840. They are not in the NGS database. They are handsome but worn marble obelisks about three and a half feet tall; one is on the north side of Main Street opposite the intersection with Fair Street, and the other is about 340 feet south up Fair Street on its west side. A few years ago, local astronomers checked it out with a K&E transit and found it to be 3.5 plus or minus .8 minutes off, which they considered too big an error for a skilled operator in 1840. They guess that construction disturbances caused the error.

 

The more recent set was placed in 1887, and consists of three octagonal stone posts originally about two feet high. They are in the NGS database; south to north, they are LW4252, LW4251, and LW4184. Fiddling with their coordinates with one program or another will demonstrate that they are not dead on true north either; the data sheets put the error at 28 minutes. It should be noted here as elsewhere that the south stone was broken off below ground level many years ago, but its base is still in place about nine inches from the surface of the ground. The south and north stones are 132.7776 meters apart, and the middle stone is a little over a meter north of the mid-point.

Share this post


Link to post

Thanks everyone for the info on meridian markers, much appreciated.

 

When looking at the MERIDIAN UT benchmark posted by GEO*Trailblazer 1 above, I was amazed at the number of recoveries logged. I counted 111. Most by usually-not-benchmarking geocachers, of course, but logs nonetheless. Apparently there is a geocache in the area that attracts them, and the meridian benchmark gets "found" as a secondary activity.

 

That might qualify as the most correct logs for any one benchmark. Even beats out the one at Four Corners (AZ/NM/CO/UT) unless one adds in the recoveries from the destroyed BM with it.

Share this post


Link to post

The Principal Meridians and Base Lines of the Public Land Surveys, as far as we know, rarely or never coincided with the shorter meridian lines discussed above. Their purposes are different. The short meridian lines were laid out so that surveyors in the locality could calibrate their compasses. The PLS meridians and base line parallels of latitude established intersections from which the townships, sections, and smaller divisions of sections could be numbered and located. The PLS required regular astronomical checks of the meridian lines, rather than much use of the compass. Nevertheless, this map is a great help to anyone concerned with the history of the Public Land Surveys.

Share this post


Link to post

If I'm not mistaken, that is one of the drawbacks of being one of the original 13 colonies. Different history in terms of land survey. Maybe someone else can elaborate. Doesn't explain ALL the missing ones above, but some.

Edited by Klemmer & TeddyBearMama

Share this post


Link to post

In New Jersey, for instance, there were no 'public lands'. Thus no need for PLS survey. Any land not owned by anyone else belonged to the East or West Jersey Board of Proprietors.

Share this post


Link to post

Meridian Stones have cropped up here several times in the past. And they have little to do with the Principal Meridians and Baselines established as the basis for the Public Land Surveys. In fact they are primarily found in older states where lands and land claimswere being surveyed (probably as late a1 1900) principally by the magnetic survey compass.

 

Do a search on the term "True Meridian" and your state. You may find that there is or has been legislation which provided for the establishment of meridians in local areas to assist the local surveyors. It was a really good idea, but it doesn't seem like they were used as much as one would like. Many of these laws are still in effect, although not used for maybe 100 years.

 

Given a set of posts established on the true astronomic north merdian, surveyors could come to the line, set up their survey compass and set off the proper magnetic declination so that their compass would read north when pointed north. The needle on the compass points along the lines of the earths magnetic field, which differ from true north. The difference which can be referred to as variation or declination varies with location and changes with time. A good survey compass had a provision to set off this value (some with a vernier) so that the reading on the compass (the needle points to corresponds to ) 0 or north when the compass is sighted north. At that setting all the bearings read from the compass will correspond closely with the 'true meridian', or astronomic north.

 

If all the surveyors in a county or small region set their compasses this way every year or so, then all the surveys they performed 1) would be on or close to a true and consistent basis of bearing, 2) would match each other and 3) would not be subject to WHEN they were done.

 

I think I posted on the topic, perhaps in the geocaching forum, a few years ago when one particular stone was found.

 

If I find my post, I will copy it up here.

 

- jerry wahl

Share this post


Link to post

Folks should be aware of CGS Special publication #110, "Astronomic Determinations" (1925) (which you can down load from the NOAA Special Publication site). It has a huge list of all the stations in all the states including the original 13. These stations weren't quite the same as the one's used by local surveyors, but were used to determine latitude, longitude (using telegraph) and azimuth in the early surveys including that of the Eastern Oblique Arc.

 

Here's the link: http://docs.lib.noaa.gov/rescue/cgs_specpu...s_specpubs.html

 

The historic publications obtainable from this site is nothing short of a treasure trove.

Share this post


Link to post

Lots of interesting stuff here.

 

I can't seem to get #13 (1922) to load. Does anybody find it?

The requested URL /rescue/cgs_specpubs/QB275U35no131922.pdf was not found on this server.

 

Did I miss where to find an index?

Edited by Bill93

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  
Followers 0

×
×
  • Create New...