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How Important Are Bechmarks...


gbod
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I am hoping someone that surveys or makes maps for a living can answer this.

 

I have noticed that responses to questions about bechmarks in the forums here imply that benchmarks are archaic relics from times past. (Of course I mean bechmarks in the GC.com sense: horizontal and vertical control stations.)

 

My observation about the $250 fine not going up over the last 100 years brought this response:

Yes but I think its not as big of a deal then they were back then. My dad is a Civil Engeenier and he told me most of the time they dont even need to use the benchmarks for work its just SLIGHTLY more convenent. He said if he didnt have it to work with (which most of the times he doesnt) they just use there own technology if they need to.

 

Another question about not finding a benchmark illicited this reply:

I would be suprised if many people cared about lost benchmarks, aside from hunters from this website or another like it. We don't really need them anymore, as maps are in great abundance & within easy access.

 

Looking forward to hearing your responses! :lol:

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I'm no professional surveyor, but I think they are pretty important. While I was in school, I spent a summer helping a geology professor with a Gravity survey he was doing. He was trying to find buried faults, in odrder to help deliniate aquafers, or groundwater for wells.

 

In order to properly process the gravity data, we had to know the precise locations & elevations of the gravity stations. This was during the days of SA (1997), and the geology department did not have any differential gps gear, so we had to use tradtional transit surveying. All of our surveying was tied into benchmarks. We couldn;t have completed the study without it.

 

From what I understand, in order to do real surveying with a gps, you still have to tie it into a benchmark.

 

BTW, there were several times when we spent most of a day just trying to find a benchmark, just using a datasheet. It was lots of fun. I just wish that I could remember where they all were, so I could log them. When I finally found geocaching and benchmark hunting, I knew it was for me!!!

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While the posters to this site refer to all survey control monuments as bench marks, in reality that term is appropriately applied to monuments that have a very accurately determined elevation. It is certainly true that in many cases engineers don’t necessarily care about these marks because the vast majority of their projects are small and only require differences in elevations and only occasionally worry about the absolute value of the bench marks. These marks serve a very important part of our national infrastructure by providing a consistent height reference surface and accurate reference system for many applications including: topographic mapping, accurate air and marine navigation, storm evacuation route planning, flood plain mapping, effective applications of fertilizers and pesticides, efficient and reliable water delivery systems, detection and monitoring of crustal motion such as was recently reported in the national news about the Louisiana Coast. This is only a partial list. I hope this gives some insights into the importance of these small monuments.

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As a Professional Land Surveyor, I use these Traverse Stations and Bench Marks on a regular basis.

 

Many of my projects need to be tied into a known datum.

 

These marks are still very important. They were not established just for the purpose of preparing maps. They are needed to determine exactly where on the globe a particular property or structure is located.

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Benchmarks can be 'relics from times past', however they are far from archaic. It's already been stated (restated) that the benchmarks we search for are important in a very real sense, althought the level of importance may vary between different types of surveys and/or projects. Many public agencies such as local governments, water districts, and utility companies, along with private firms use the survey control established by the NGS (USGS, USC&GS, etc.) daily on their engineering and survey projects, in one way or another. While the NGS data might not be directly used for a given project (the project may require the use of a more localized datum) often times the survey control that is used can be tied back to the NGS geodetic marks and data.

 

The marks we seek are simply (if the term simple can be used here) the framework for the geodetic survey control network for the nation and the smaller regional, county, city, and individual survey control networks are developed using the benchmarks of that framework as a tangible startpoint, allowing surveyors and engineers across the nation to be using the same datum to give relativity between projects, whether across town or across the nation. The benchmarks may be seemingly old and unused 'relics', but the framework they represent is very much in use.

Edited by Kewaneh & Shark
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In our surveys that had anything to do with water; i.e. culverts, bridges, erosion, etc had to be tied to NAVD 88 datum . It was required for the permits from all the state and federal government agencies. It was not unusual for our survey crews to runs levels for miles to get to a published mark just to determine high water at a stream crossing a state or federal highway.

 

Also, all of our aerial mapping had to be based on NGS control, both horizontal and vertical.

Edited by elcamino
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Thanks for all of your interesting and informative replies. Next time someone asserts that benchmarks are not important, you can reference this thread! :unsure:

 

(Of course this thread may have more credibility if I had actually spelled benchmark correctly in the tiltle!)

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Another point from this amateur: IF benchmarks and horizintal control points are not important, THEN why does soemone spend so much time, paint and ribbon marking and placing stakes near NGS disks? I estimate that well over 1/2 of the marks that I find have paint. ribbons or wooden stakes nearby. Of course probably I can only find those easy ones that are well marked. :lol:

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