How can benchmarks possibly be helpful to anyone?

[Rubbertoe]

Okay, I could understand it if a city was littered with benchmarks - it might help surveyors get measurements a little easier... but how on earth can a few benchmarks peppered over many miles really help with anything?

 

I live near Lancaster Ohio, and there really aren't that many benchmarks around - here is an overhead view of the town, along with the benchmarks in the area, as downloaded from this site: Lancaster Ohio Map Link

 

As you can see, it doesn't really look like there are enough marks to help with anything... and, the few that I've found so far - quite a few of them were considerably off from the posted coordinates.

 

Just wondering the logic of these little disks. []

 

Rubbertoe - Webcam - Image Archives

--== http://www.bigfoot.com/~rbatina ==--

[+unclerojelio]

You are only seeing USGS benchmarks in the database. Many other organizations have used them as starting points to fill in the empty spaces.

 

... Two roads diverged in a wood, and I--

I took the one less traveled by, ...

 

unclerojelio

[Magellin]

However, I do belive that a BENCHMARK is SUPPOSED to be very easily seen/found (light house, courthouse, church) There should be at least 2 in an area with some line of site. This would be a starting point for ANYONE to locate an area (like my property that the neighbors have a cattle graizing on :-)).

 

A Land Boundry Marker (LBM) would be placed by any organization that has the authority to do so, like the U.S. gov, State, County and as well as private survayors.

 

Although I have no idea what I'm talking about.

 

Now if I can only find that rock I dropped into the shag carpet.

[survey tech]

Rubbertoe

Unclerojelio is correct. Imagine a giant fish net covering the entire country. This is what the network of control markers looks like. Your city may lie in one of the gaps or holes in the net. But in fact I'm quite sure that there are plenty of markers all around you, set mostly by private surveyors and some by local government agencies, that are unknown to the public. Remember that most benchmarks have only approximate coordinates, for the purpose of referring you to the right USGS quad map for you to use to find the marker. So trying to use GPS to find these markers will usually be misleading. The best way to find them is to use the description in combination with the appropriate map. Horizontal control points, such as Triangulation Stations, however, will always be found precisely at the coordinate location given in the description.

 

Magellin

I think you are also confusing horizontal control points with vertical control points. You are right that horizontal control points should ideally have a wide range of visibility to be most useful, still there are many that do not, due to local circumstances. Benchmarks, which are vertical control points, have no such requirement and can be useful regardless of visibility. So you will find benchmarks in many seemingly bizarre locations. Also, benchmarks are in no way connected to land boundaries, they are used for mapping, civil engineering and construction purposes and are vital to our economy.