NGS Reference Mark Question

> The datasheet has a geodetic bearing and distance in meters from the station. Is it possible to use the lat/long of the station, and then use the geodetic azimuth and distance to calculate the coordinates of the two reference marks?
I suppose so, after all, that's basically what the reference marks are for, but ...

"...The horizontal coordinates were established by classical geodetic methods and adjusted by the National Geodetic Survey in February 2000.... The orthometric height was scaled from a topographic map...."

The position you get isn't going to compare to OPUS very well.

Thanks for the quick reply.

I am trying to get close to state plane. It doesn't have to be supertight, but I want it close.

There are not many horizontal monuments in the area that I can find too easily, and occupy with the GPS.

Yes, and they would be almost of the same positional quality as the main station.

I have found that as good as the triangulation teams could locate stations tens of km apart, they often had some difficulty getting accurate obs to the reference marks. Not sure what the reason for this is. So, it depends on how far apart they are, how far away was the azimuth mark, what the terrain was like in between, etc. But certainly you could use that info to compute decent positions for those marks. As Norman said, though, this was a third order station, never GPS'd in the NSRS, so don't expect it to match a HARN or CORS better than to a decimeter at best (nor does it have 2007 or 2011 coords). But, I have used that method to get a decent NAD27 or NAD83 (1986) coordinate.

> I have an older datasheet for NGS Monument GD1801. It is a third order horizontal monument, and was reset in 1970.
I had a similar situation this spring. Station LOGAN was within the limits of my project. The station mark itself had been unearthed and vandalized. A 2' lump of concrete was on the surface and the brass disk had been chiseled off. But 2 reference marks were nearby and undisturbed.

National Geodetic Survey, Retrieval Date = MARCH 8, 2013
FJ1087 ***********************************************************************
FJ1087 DESIGNATION - LOGAN
FJ1087 PID - FJ1087
FJ1087 STATE/COUNTY- OK/KINGFISHER
FJ1087 COUNTRY - US
FJ1087 USGS QUAD - CASHION (1981)
FJ1087
FJ1087 *CURRENT SURVEY CONTROL
FJ1087 ______________________________________________________________________
FJ1087* NAD 83(1993) POSITION- 35 50 30.38724(N) 097 44 44.03297(W) ADJUSTED
FJ1087* NAVD 88 ORTHO HEIGHT - 322.90 (+/-2cm) 1059.4 (feet) VERTCON
FJ1087 ______________________________________________________________________
FJ1087 GEOID HEIGHT - -27.35 (meters) GEOID12A
FJ1087 LAPLACE CORR - -2.11 (seconds) DEFLEC12A
FJ1087 HORZ ORDER - THIRD
FJ1087 VERT ORDER - THIRD ? (See Below)
FJ1087
FJ1087.The horizontal coordinates were established by classical geodetic methods
FJ1087.and adjusted by the National Geodetic Survey in November 1994.
FJ1087.
FJ1087.The NAVD 88 height was computed by applying the VERTCON shift value to
FJ1087.the NGVD 29 height (displayed under SUPERSEDED SURVEY CONTROL.)
FJ1087
FJ1087.The vertical order pertains to the NGVD 29 superseded value.
FJ1087
FJ1087.The Laplace correction was computed from DEFLEC12A derived deflections.
FJ1087
FJ1087. The following values were computed from the NAD 83(1993) position.
FJ1087
FJ1087; North East Units Scale Factor Converg.
FJ1087;SPC OK N - 93,427.145 622,985.650 MT 0.99996147 +0 09 00.6
FJ1087;SPC OK N - 306,518.89 2,043,912.09 sFT 0.99996147 +0 09 00.6
FJ1087;UTM 14 - 3,967,125.377 613,287.552 MT 0.99975814 +0 44 04.6
FJ1087
FJ1087! - Elev Factor x Scale Factor = Combined Factor
FJ1087!SPC OK N - 0.99995362 x 0.99996147 = 0.99991509
FJ1087!UTM 14 - 0.99995362 x 0.99975814 = 0.99971177
FJ1087
FJ1087: Primary Azimuth Mark Grid Az
FJ1087:SPC OK N - LOGAN AZ MK 086 19 15.5
FJ1087:UTM 14 - LOGAN AZ MK 085 44 11.5
FJ1087
FJ1087|---------------------------------------------------------------------|
FJ1087| PID Reference Object Distance Geod. Az |
FJ1087| dddmmss.s |
FJ1087| FJ1080 CRESCENT MUNICIPAL TANK APPROX.18.3 KM 0472641.0 |
FJ1087| CL4775 LOGAN AZ MK 0862816.1 |
FJ1087| CL4778 LOGAN RM 3 14.947 METERS 16421 |
FJ1087| CL4776 LOGAN RM 1 15.015 METERS 16444 |
FJ1087| CL4777 LOGAN RM 2 15.081 METERS 26658 |
FJ1087|---------------------------------------------------------------------|
FJ1087

Calculating the station position by double distance off the reference marks I get an SP position of N306520.05 E2043911.77 on my redundantly OPUS'd and LS adjusted project control. That differs from the datasheet by 1.16' in the northing and 0.32' in the easting. Note that the datasheet position is NAD83(93), and the project control is NAD83(2011).

Are Not NGS Reference Mark Usually Visible Without A Tower?

Where I have looked for Reference Marks they appear as if they could have been located by an instrument on the ground after the tower was removed. Possibly set only from backsighting the azimuth mark. Some may not be possible to observe today with tree growth. If they were set after the tower was removed, something other than the main instrument could have been used. Using the main instrument from the tower would result in significant vertical angle which could also be a source of additional error. More probably just a less precise instrument,

NGS has much more information for each point than is included on the data sheets. Every reference mark I have found has it's own data sheet, but searching for one at this specific time is impossible.

There is one nearby that I have GPSed and have found both reference marks, but never found the azimuth mark. Someday I hope to set on the mark, sight the reference marks and get a better search location.

Paul in PA

Playing in Google Earth, I just found this LINK for the first time.

Are Not NGS Reference Mark Usually Visible Without A Tower?

Usually the azimuth marks (and reference marks) were visible from the ground. The angles between them were measured from tripod height.

Most reference marks do not have individual datasheets UNLESS they were occupied as part of a survey or if they are also a benchmark. In both cases they would have their own PID. Sometimes a later occupation of a station would use one of the RM's, or they would set a new RM to occupy for whatever reason.

There are also the cases of the "RM A" stations, which were set in the TCT surveys (Transcontinental Traverse). These stations are set about 30 m or so from the main station, so as to form very narrow diamond shaped figures (i.e. every other station had a RM A set). Not all parts of the TCT (done at different times in the 60's-70's) have this configuration. The same obs (angles and EDM distances) were taken at the RM A as at the main station. One of them often had astro obs as well.

h 10974770 LAUREL RM 3 N394955.31663 W0792603.34928 A 83 JW1259 PA 051 1975 (1992)
h PAC_SAC= [ ]
h h
h 10974770 LAUREL RM 3 JW1259
h ST/COUNTY= PA/(051)FAYETTE
h STAMPING =
h MONUMENT = DR REFERENCE MARK DISK
h SETTING = 80 SET IN A BOULDER
h STABILITY=
h MAGNETIC =
h

h
h LAST RECOVERED
h TYPE COND DATE AGENCY SAT TRANS PACK
h ---- ---- -------- ------ --- ----- ----
h H S 1975 NGS P
h
h (Year=1975 Agency=NGS Type=U Cond=S)
h ------------------------------------------------------------------------
h THE STATION IS ABOUT 4 MILES WEST-NORTHWEST OF CONFLUENCE, 5
h MILES SOUTHEAST OF OHIOPYLE, ON THE SUMMIT OF LAUREL RIDGE AND
h ON PROPERTY OF THE PENNSYLVANIA STATE FOREST SERVICE. PERMISSION
h WAS GIVEN BY ROBERT ACHE, DISTRICT SUPERVISOR, OF LIGONIER.
h TELEPHONE- 412-238 9533.
h
h TO REACH THE STATION FROM THE JUNCTION OF U.S. HIGHWAY 40 AND
h STATE HIGHWAY 281 NORTH, NORTHEAST OF MARKLEYSBURG, GO NORTHERLY
h ON HIGHWAY 281 NORTH FOR 5.2 MILES TO A SIDE ROAD LEFT AT A CHURCH
h ON THE RIGHT. TURN LEFT AND GO WESTERLY ON A PAVED ROAD FOR 2.75
h MILES TO A SIDE ROAD RIGHT. TURN RIGHT AND GO NORTH ON A ROCKY
h ROAD, FIRETOWER ROAD, FOR 0.55 MILE TO A FORK. BEAR LEFT AND
h CONTINUE NORTHERLY ALONG AN OLD TELEPHONE LINE ROAD FOR 0.1
h MILE TO A DIAGONAL CROSSROAD. TURN LEFT AND CONTINUE NORTH FOR
h 0.05 MILE TO AN OLD LOOKOUT TOWER AND THE STATION ON THE
h RIGHT.
h
h THE STATION MARK IS A STANDARD DISK, STAMPED---LAUREL 1927 NO 3
h 1975---, CEMENTED IN A DRILL HOLE IN A 3 BY 3 FOOT BOULDER THAT
h PROJECTS ABOUT 1 FOOT ABOVE THE GROUND. IT IS 34.6 FEET WEST OF
h THE SOUTHEAST LEG OF THE LOOKOUT TOWER AND 42.0 FEET SOUTHEAST OF
h THE NORTHEAST LEG OF THE TOWER.
h
h REFERENCE MARK 4 IS A STANDARD DISK, STAMPED---LAUREL 1927 NO 4
h 1975---, CEMENTED IN A DRILL HOLE IN A 1 BY 5 FOOT BOULDER THAT
h PROJECTS 2 INCHES ABOVE THE GROUND. IT IS 24.5 FEET WEST-SOUTH
h WEST OF THE SOUTHWEST LEG OF THE TOWER, 42.8 FEET WEST OF THE
h SOUTHEAST LEG OF THE TOWER AND ABOUT 2 FEET HIGHER THAN THE
h STATION.
h
h LAUREL 1927 IS A STANDARD DISK, STAMPED---LAUREL 1927---, CEMENTED IN
h A DRILL HOLE IN A 6-FOOT TRIANGULAR SHAPED BOULDER THAT PROJECTS
h 30 INCHES ABOVE THE GROUND. THERE WERE NO PROMINENT OBJECTS TO
h REFERENCE THE MARK FROM.
h
h THE DISTANCES BETWEEN MARKS WERE NOT MEASURED DUE TO TREES AND
h BRUSH. CLEARING WAS PROHIBITED.
h THERE WAS NO SUITABLE LOCATION FOR AN AZIMUTH MARK.
h HEIGHT OF LIGHT ABOVE MARK, 22.7 METERS.
h

Not to be confused with U-SMART

DDSM:beer: