Reset Benchmark

[+bvrballs]

I am new to benchmarking and have recently started submitting recovery notes to NGS. I am not sure how to recover this one, so I thought I would ask here.

 

When approaching the BM, the coordinates on GC.com were surprisingly accurate, which made me think there was a problem. Te description from '54 indicates the mark to be underground. The mark I recovered is not only set at curb level, but is also stamped 1988. The number (it is a city of Long Beach mark) matches the description. Placed a call to the city engineer who told me the original mark was destroyed in 1987 and replaced, in a slightly new location. It is now about 10' south and 1.8' West of the original. I have the correct updated description and height (in NGVD 29) direct from the city engineer.

 

So, how do I report it. Is this a destroyed BM and a new one, or is this a recovery with an update of a reset mark?

[holograph]

You should report "not found", and include what you discovered from the city engineer about the mark being destroyed. The fact that a new mark was set 10 feet away is almost irrelevant, other than noting that it is not the station described by the datasheet.

 

You can attempt to get the station status set to destroyed, but generally the NGS requires you to have the old disk in hand, or to submit photographic evidence showing the old disk out of position.

[+Black Dog Trackers]

bvrballs -

 

Welcome to benchmark hunting!

 

It isn't easy. Concerning your find, which I believe is DY0381, none of the logs of it are correct. The 1988 disk that was photographed is not a find of DY0381. In order to righly post Found It, you must find a disk which is marked "114 C OF LB".

 

As Holograph says, you should report Not Found for DY0381. It would be very useful if you could also take a picture of the mark and state in your Not Found log that the 1988 disk pictured is not DY0381 so that other people looking for DY0381 will be less likely to log Found It in error.

 

There are thousands, probably hundreds of thousands of disks, that are not included in the GC database because they are not on the NGS database, and GC got its copy of the NGS database around 2000. Occasionally, these are near the same place where a disk on the NGS database no longer exists or is no longer accessible. In these cases, I figure the local surveying community misses that marker and gets a new one set. What you found is probably such a case. However, as is also common, whoever set the 1988 disk did not submit its data to the NGS, so it is not in the NGS database.

 

The main point here is that in order to be able to claim Found It, you must find the exact disk described. In this case, it's a disk that existed in 1954 and was marked "114 C OF LB".

 

Another issue is how 'far off' the coordinates on a datasheet are. Note that on the datasheet for DY0381, 2 lines under the coordinates, are the words "location is SCALED". This is extremely important to note when hunting a disk. It means that the coordinates can be as much as a few hundred feet off. Other datasheets say "location is ADJUSTED". The coordinates that say that are much more exact than you can measure with a handheld GPS receiver.

[+BuckBrooke]

bvrballs,

Once you're done logging with the NGS and Geocaching (Not Found as well), I would suggest you log this mark as a Waymark, </a>. I haven't seen a City of Long Beach disk before, and don't have a link/picture of one on the benchmarkign agency <a href="http://www.unm.edu/~creelbm/pages/agencies.html" target="_blank">site. Could you send me a photo, or put it on Waymarking so I could link to it? Thanks.

 

Good work on figuring out the disk.

 

Oh, figured out the link to the photos, thanks BDT. Very obvious.

Edited August 3, 2006 by BuckBrooke

[+Harry Dolphin]

Sometimes the resets are listed, as well as the original: KV0152 KV0153

On the other hand: This is the reset, not listed, for one not found: OB0163.

Found another pair where the mark and the reset were listd as being within inches of each other. The original mark is now listed as destroyed.

[+bvrballs]

You should report "not found", and include what you discovered from the city engineer about the mark being destroyed. The fact that a new mark was set 10 feet away is almost irrelevant, other than noting that it is not the station described by the datasheet.

 

You can attempt to get the station status set to destroyed, but generally the NGS requires you to have the old disk in hand, or to submit photographic evidence showing the old disk out of position.

 

I never got the city engineer to admit it (maybe he didn't know the full history), but the area looks to me like they did road and/or sidewalk work in the area about that time. I suppose I could measure it out and take a picture of the new sidewalk where the underground mark used to be, but somehow I doubt they would buy it.

 

So the message I get is, the mark is the mark. Any other mark is a different mark. Got it. Will report correctly. Now if I could just get NGS to accept the new mark . . .

 

I suppose they don't have a way for us to report new marks to them. Oh, well.

 

Scott

[+bvrballs]

bvrballs -

 

Welcome to benchmark hunting!

 

--- snip ---

 

Another issue is how 'far off' the coordinates on a datasheet are. Note that on the datasheet for DY0381, 2 lines under the coordinates, are the words "location is SCALED". This is extremely important to note when hunting a disk. It means that the coordinates can be as much as a few hundred feet off. Other datasheets say "location is ADJUSTED". The coordinates that say that are much more exact than you can measure with a handheld GPS receiver.

 

Thank you.

 

As for the coordinated being off. I realize that. My comment was kind of tongue in cheek. I was actually surprised to walk up on the listed coords and find a disk. This is actually harder then geocaching, but I think I will find it more rewarding in a way.

 

I run with a club and have found it easy to load caches in the GPS without any hints and have been quite successfull. Can't do that with benchmarking. I think this will be a hobby that requires considerably more planning.

 

Scott

[holograph]

I suppose they don't have a way for us to report new marks to them. Oh, well.

 

Well, the NGS does accept reports of new marks, but they require rigorous documentation, copies of the original survey notes, and proof that the survey met the standards for inclusion into the NSRS. That's something that even professional surveyors find burdensome. The process is called "blue booking", named after the standards document that describes the process.

[Z15]

I reset many NGS Bench Marks and assisted the NGS adivsor in resetting a few triangulations stations, one we repositioned with GPS back in 1992. ANY MARK THAT IS RESET IS AUTOMATICALLY DOWNGRADED TO THE LOWEST LEVEL ACCURACY, I.E. 3RD ORDER BECAUSE THE INTERGRITY OF THE MARK IS IN QUESTION.

 

Its it lot of work, the survey part also but building the mark can take a day sometimes if you have to dig a hole 5ft deep x 12-in dia and pour concrete. Often get 2 ft and hit rock and start over. Its going to cost you money for materials, not reembursed.

 

I have seen some BM's that were reset by local agencies or private firms and they never documented the field work so the elevation is untrustworthy. No checks on the field notes. To a great many close is good enough but is a sin in the surverying professional to have that attitude.

 

I even encountered someone who dug up a concrete post and moved it out of his way. If I had not been to that BM before within months, its possible it would have beena accepted as original due to the many changes in the area. That mark was destroyed under direction of NGS.

Edited August 4, 2006 by Z15