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Church Spires as Benchmarks

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What criteria is there for listing Church Spires as Benchmarks?


The reason I ask, is that I have a geocaching friend in New Jersey whom has logged quite a few church spire benchmarks.

Yet, here in southwestern Ohio where I live and cache, there is a proliferation of high church spires, none are listed as being benchmarks.


Is it a state to state thing? If so, that makes no sense to me.




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I don't think it's an State thing, maybe an age/area thing.

Figure most large, 100 year old stone churches are still gonna be around a while.

We've seen some at court houses, post offices, and old schools too.

With benchmarks simply mapped points, probably better there than a spot maybe eventually taken over by development. :)

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And as far as the NGS is concerned they no longer qualify for recovery. They do not want reports on intersection stations any more. So the only place you should record them is on this site.

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Ditto what mloser said.


Some background in more detail:

The list of data sheets includes four kinds:

1. True bench marks, i.e. vertical control marks having ADJUSTED elevation and typically loose coordinates.

2. Triangulation stations, having ADJUSTED coordinates and typically loose elevation. These were occupied with instruments to take sights to other points and are the most accurately known among the "classical" control points.

3. Intersection Stations such as spires, tanks, towers, and chimneys. These were not occupied, but were sighted upon, mostly as a check on the data for triangulation stations. This gave them pretty good coordinates, but not as well-checked as the triangulation stations.

4. More recently, stations measured by GPS. The horizontal is great and the vertical is not in the same measurement system as the classical bench marks.


There are also a few older stations serving both horizontal and vertical purposes.


Elevation bench marks are still of great importance, at least for the next several years until NGS puts out a new GPS and gravity-based vertical datum, and it is adopted by all users, including the national flood insurance program, the Corps of Engineers, and cities that haven't all moved even to the current datum.


Triangulation stations are of decreasing importance due to widespread use of precision GPS, but still are of interest to NGS.


Intersection stations are a.) less accurate, b.) often moved slightly over time by maintenance and nature, and c.) not readily occupied by GPS to allow future use, so NGS has pretty much given up on them.


The lack of intersection stations in your area could be due to you not having any stations of the triangulation network in your immediate vicinity. The elevation and coordinate surveys were essentially independent. Each network was a fishnet mesh stretched across the country and sometimes the holes were 20 miles or more wide. The networks generally don't coincide.


The stations were chosen by different criteria. For vertical (elevation) work you want nice clear sight lines for 300 yard/meter increments, and as few hills as practical. Thus they frequently followed railroads and roads.


For horizontal coordinates, you want to see as far as possible, from a Bilby tower if necessary, so stations were placed on the higher spots available and several miles apart.

Edited by Bill93

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