A couple of data sheet questions

[+m&h]

Yesterday we located a couple of marks each of which raises a small question concerning one item in its data sheet. Both are along Carmel Valley Road in Monterey County, California.

 

GU2098, GWM2 USGS, exhibits many characteristics of a bench mark disk. The words “Bench Mark” are part of its logo casting; its stamping includes an elevation; it has no horizontal order. Yet its marker type in the rundown is given as DD = Survey Disk. What is there about the mark that makes this so?

 

GU2100, X 703 RESET 1951, is a standard USC&GS Bench Mark disk, yet the setting agency is given as CA-053 (Monterey County). Does this happen often? It’s a new experience for us, or so we think.

 

If either of these involves a data sheet error, is it worth letting anyone know? We sent a county correction to Deb Brown in mid-February, and it hasn’t shown up in the database. (That would be DV1977, GATEWAY, listed in Maricopa County, but actually in La Paz County.) We aren’t interested in bombarding the swamped with trivia, but we aren’t fully at ease deciding what’s trivial, either.

[+PFF]

An interesting set of circumstances surrounding each disk. However, I don't see anything which suggests an error. Perhaps NGS or one of our professional surveyors will weigh in on the issues.

 

My theory is that in 1968, NGS made a pass through the area and upgraded some previously-existing marks to NGS standards. Notice that credit to the other agency is given in the HISTORY section of the data sheet, but NGS wrote the DESCRIPTION.

 

In contrast, when the monumenting agency establishes a mark to a high standard, I've noticed that the monumenting agency's description appears (with a data matching the monumenting date). However, with GU2098 and GU2100, the description was written many years after monumentation, and not by the monumenting agency.

 

I'd consider these to be two "regular" marks with scaled coordinates. And it is normal for USC&GS stations to have scaled horizontal coordinates. It would seem that NGS made a good decision, here. If an accurate station was needed in a particular location, it would be more efficient to upgrade an existing mark, rather than setting a duplicate in the immediate vicinity. Besides, it's possible that USC&GS got there first and took the best mounting spot on the rock.

 

Meanwhile, I'd give an "attitude award" to NGS for not being on an ego trip; i.e., for being willing to include in the data base, benchmarks with good stability, set by other agencies--rather than insisting that every mark be stamped with the NGS name!

 

-Paul-

[+m&h]

Thanks, Paul!

 

One question we'd like to put more clearly is this, concerning GU2100: If Monterey County set the disk, why isn't it a Monterey County disk? We've seen plenty of the "non-ego-trip" sort, where NGS has added a state or county or other agency (USGS, say) disk to its database. What we don't recall seeing is evidence that NGS has shipped their disks out to other agencies for setting. Does that happen?

 

Our question about GU2098 was based on an assumption that "Survey Disk" is something more precise than a generic term, but we're having trouble finding in the Blue Book or the like anything that gives the term "SURVEY DISK" particular functions or characteristics. So maybe that one was actually downgraded (the vertical control being not so hot)?

 

Anyway, we're happy with the prospect that there aren't any reportable errors here.

 

Cheers,

[Papa-Bear-NYC]

Thanks, Paul!

 

One question we'd like to put more clearly is this, concerning GU2100: If Monterey County set the disk, why isn't it a Monterey County disk? We've seen plenty of the "non-ego-trip" sort, where NGS has added a state or county or other agency (USGS, say) disk to its database. What we don't recall seeing is evidence that NGS has shipped their disks out to other agencies for setting. Does that happen?

 

...

 

Cheers,

I think the use of NGS (and certainly of CGS disks prior to the 70s) by other groups was not uncommon. I've seen it myself with the IBC using CGS disks for triangulations. It's not every agency or group that has a bunch of disks ready made so I think there was a fairly regular channel to acquire them from the "Feds". Perhaps George (NGS Surveyor) would know the ins and outs of this. Edited April 14, 2008 by Papa-Bear-NYC

[NGS Surveyor]

Here are my thoughts:

For the USGS disk, the current definition for code DD is “Survey disk (other agency)”, see: http://www.ngs.noaa.gov/PC_PROD/DDPROC4.XX...ation.html#A.11 , Section A.12. I also asked our database expert and he says that “DD”, to him, has always meant a disk from another agency. For those not aware, USGS stands for U.S. Geological Survey, and this is different from USC&GS which stands for U.S. Coast & Geodetic Survey (now National Geodetic Survey). These two offices are in different parts of the government.

 

Regarding the other disk listed as set by Monterey County, it may very well have been set by county surveyors as part of a cooperative project with USC&GS/NGS. Over the years, many cooperative projects were done in which a state or local government did some or most of the field work. Cooperative projects still go on today.

 

GeorgeL

NGS

[+m&h]

Many thanks for that helpful response. It moved us to go through our own small database of found marks, to find that our 36 DD's are indeed all either other agencies or, in a small number of instances, cooperative efforts. We're grateful.

 

Cheers,

[Z15]

When ever we reset a NGS mark, this is how it would appear. The NGS advisor provided us (DOT) with a supply of disks and witness posts to move marks and we did all the filed work, sent it to him and he did the rest.

 

AE9966_MARKER: DV = VERTICAL CONTROL DISK

AE9966_SETTING: 66 = SET IN ROCK OUTCROP

AE9966_STAMPING: E 329 RESET 1998

AE9966_MAGNETIC: N = NO MAGNETIC MATERIAL

AE9966_STABILITY: A = MOST RELIABLE AND EXPECTED TO HOLD

AE9966+STABILITY: POSITION/ELEVATION WELL

AE9966

AE9966 HISTORY - Date Condition Recov. By

AE9966 HISTORY - 1998 MONUMENTED MIDT

AE9966

AE9966 STATION DESCRIPTION

AE9966

AE9966''DESCRIBED BY MICHIGAN DEPARTMENT OF TRANSPORTATION 1998 (SHN)

AE9966''STATION IS LOCATED AT NEGAUNEE, ALONG US HIGHWAY 41 AND STATE HIGHWAY

AE9966''M-28, IN THE SOUTHWEST SIDE OF A LARGE PROMINENT ROCK OUTCROP

AE9966''SOUTHEAST OF THE HIGHWAY. IT IS ABOUT 0.17 KM (0.10 MI) SOUTHWEST OF

AE9966''THE JUNCTION WITH COUNTY ROAD 492 (MAAS ST) AND A TRAFFIC SIGNAL, 16.3

AE9966''M (53.5 FT) NORTHEAST OF THE CENTERLINE OF THE NORTHEAST DRIVE

AE9966''ENTRANCE TO THE FERRELL GAS OFFICE/STORE AND BULK PLANT, 10.6 M (34.8

AE9966''FT) SOUTHEAST OF THE BACK OF CURB, 5.2 M (17.1 FT) NORTH OF A POWER

AE9966''POLE, 1.4 M (4.6 FT) SOUTHEAST OF A CALCITE VEIN AT THE NORTHWEST

AE9966''CORNER OF THE ROCK OUTCROP, 0.55 M (1.80 FT) NORTHEAST OF A CARSONITE

AE9966''WITNESS POST, AND 0.3 M (1.0 FT) EAST OF THE NORTHWEST CORNER OF THE

AE9966''LOWEST LEDGE ON THE SOUTHWEST SIDE. A STANDARD VERTICAL CONTROL DISK

AE9966''SET IN A DRILL HOLE ABOUT 1.1 M (3.6 FT) ABOVE LEVEL WITH THE HIGHWAY.

AE9966''DESCRIBED BY MIKE RAFFAELLI, SURVEY TECH - MIDT.

Edited April 18, 2008 by Z15