Bottom of marker disk?

[Little Longhaired Outlaw]

Does anyone know what's on the bottom of the disks, and are they all the same? I've been looking for a specific bench mark and all I've found is a block of concrete, similar to the 'concrete posts' I've found several other disks attached to. This one has a rectangular void about 1-11/2" X maybe 3" and about an 1 1/2 deep, like something was mounted in it that's no longer there. From the description of this mark, it should still be there, but I can't find it......

 

Wherever you go.......... there you are!!

[+Kewaneh & Shark]

Most brass disks that are mounted in concrete or stone have a stem, or anchor, of sorts attached to them that is inserted into a drilled hole. The disk is cemented or epoxied in place and only the top disk can be seen. When a disk is removed, it leaves a hole like you've described.

 

A good website to see what unset brass caps look like is Berntsen.com. They manufacture survey merkers of all shapes and sizes. Look up item 'RT35DB' on their site. It is similar to the caps used by the NGS. They also have the installation instructions (if you're curious.) It instructs drilling a hole like you describe.

 

Keep on Caching!

- Kewaneh

[+Black Dog Trackers]

I share your frustration and have also closely examined hunks of cement where a survey marker should be.

 

I think generally, benchmarks are attached to a round shaft in the cement. Fenceposts are square or rectangular.

[Wild T2]

They can be shaped all kinds of ways. The round with the flared notch is probably the most common.

 

The two "used" marks were from bridge replacements and a new bench mark was set after construction.

 

[survey tech]

Excellent examples. The stem is made thicker and stronger than the disk in order to defeat any attempts to pry the disk out of its setting. Under enough pressure the disk will crack and break, disappointing the vandal, and leaving the stem and the remainder of the disk in place.