Restamping Altitude

[+Harry Dolphin]

Curious. I'd never seen this before. KV1464

 

 

KV1464.WARNING-Repeat measurements at this control monument indicate possible

KV1464.vertical movement.

 

The data sheet does warn of vertical movement, but does not mention the additional stamping, nor when it was done, nor by whom.

 

Tossing in a few more questions...

 

 

KV1469 is listed as a triangulation station with scaled coordinates? Coords pretty far off. I have asked Deb about this one.

 

And:

 

 

KV1472 has been hit a few too many times by the lawnmowers. The center points seems in good condition. Good? Or Poor?

 

(Just in case anyone needs photos of Lafayette College disks...)

Edited October 6, 2009 by Harry Dolphin

[+Mega Scooter]

And the Data Sheet says: 195.47 (feet) Adjusted

 

MS

[Bill93]

See KV1464 data sheet. The larger characters 196.217 match the size of the date stamping and are in the position intended for elevation, so I would guess them to be oldest. The note about movement was probably added after the data sheet value was changed to 196.174, which can be found as the NGVD29 value under superseded data (conversion from meters matches 3rd decimal place).

 

Note that the size of stamping matches the college disk in the next picture, suggesting who did the restamping. Most CGS/NGS disk, of course, are not stamped for elevation.

 

The current 195.472 value (converted from meters) is in the NAVD88 datum.

 

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kv1469 has no conflict except that the stamping says first order bench mark and the NGS data sheet lists it as SECOND order vertical. It does NOT say it is a first order triangulation station. The college used one of their triangulation station disks and may have decent horizontal data on it. C&GS leveled to it to make it an elevation bench mark, which is what the college added to the stamping (somebody there was crazy about stamping). The 363.008 is the superseded NGVD29 elevation.

 

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KV1472 is probably GOOD. The elevation can still be found to pretty good accuracy by avoiding any metal which has been changed and using a point that remains on the original domed face. Horizontal position (if college has data on it) can be determined quite well. altitude is VERTCON, so it is certainly good enough for that tolerances. I see the same stamping enthusiast was at work there, too.

Edited October 6, 2009 by Bill93

[+Klemmer]

"Survey Marker Stamping 101" engineering course?

[+Harry Dolphin]

 

Yes, they seemed to be enthusiastic with stamping. A Reference Mark without an arrow!

This is Reference Mark Eight Trustees (for KV1466 Centennial. Centennial is a Lafayette College Disk with only the altitude. It is a triangulation station with two CGS reference marks.

[NGS Surveyor]

Three different, early, USC&GS survey disks, and many disks from other agencies, had blank spots for stamping the elevation. USC &GS soon learned that stamping the elevation on the disk was a bad idea. This is because the published elevation for a given mark changes over time due to: (1) the elevation determined in the field being preliminary and different from the final elevation determined by a mathematical adjustment in the office, (2) actual changes in the elevation of the disk due to land movement, (3) re-leveling of the area in later years, and (4) new mathematical adjustments of the leveling data in the area resulting in, hopefully, more accurate elevations.

 

So, it is not a good idea to stamp the original elevation on the disk, and one should not stamp anything on an existing disk.

 

GeorgeL

NGS