What type of benchmark is this?

[+Doit2it]

My guess would be an Elevation disk. What is the correct (full) name for this type disk?

It's not in the Geocaching database of Benchmarks so the only place to log it is the Waymarking website, correct?

[kayakbird]

My guess would be an Elevation disk. What is the correct (full) name for this type disk?

It's not in the Geocaching database of Benchmarks so the only place to log it is the Waymarking website, correct?

 

Doit2it

 

Obviously it is a USGS bench mark disk, not the standard Coast and Geodetic Survey disk that make up the bulk of the listings in GEOCACHING.COM. However, out west many, many, USGS marks (and not just BM's) do have PID's and maybe there is some kind of clerical error that could be determined if you would supply us with State, County, Lat/Long, presence and types of RM's, AZ or a Witness Post.

 

Remember, there on no secrets on this side of the game board.

 

According to GSAK, I have recovered to NGS 93 USGS placed marks in Montana alone. kayakbird

[+Doit2it]

State, County, Lat/Long, presence and types of RM's, AZ or a Witness Post.

 

Remember, there on no secrets on this side of the game board.

 

According to GSAK, I have recovered to NGS 93 USGS placed marks in Montana alone. kayakbird

 

Thanks for your help.

 

Tennessee

Davidson

36.052355,-86.805220 (via Google Maps)

No witness post, don't know what RM or AZ mean

 

The strange thing about this Benchmark disk is it is embedded in the porch of a building.

The Dyer Observatory was build in 1953 (the same date on the disk)

 

The really strange thing is I couldn't find where someone else had listed it on the Waymarking site.

 

Looking at this picture, the disk is just left of the front door, about 6 inches from the wall

Edited March 12, 2011 by Doit2it

[Wintertime]

My guess would be an Elevation disk. What is the correct (full) name for this type disk?

That's a triangulation station disk. Here's a log a friend of mine posted for one in Yosemite:

 

http://www.geocaching.com/mark/log.aspx?LUID=e1a48aea-95c7-4298-b845-ec2bf8f4fefb

 

As you can see from the following posting to these forums, there should also be an azimuth mark and some reference marks near the one you saw--assuming that USGS treats triangulation stations the same as NGS does.

 

http://forums.Groundspeak.com/GC/index.php?showtopic=185361

 

Patty

[+Doit2it]

As you can see from the following posting to these forums, there should also be an azimuth mark and some reference marks near the one you saw--assuming that USGS treats triangulation stations the same as NGS does.

 

Patty

 

Thanks Patty.

But if I'm using the search engine correctly (Geocaching & the NGS websites) there are no AZ or RM within 1.4 miles of this Triangulation disk. Would they be that far away, or are they just not in the database? Or am I using the database incorrectly?

[+LSUFan]

As you can see from the following posting to these forums, there should also be an azimuth mark and some reference marks near the one you saw--assuming that USGS treats triangulation stations the same as NGS does.

 

Patty

 

Thanks Patty.

But if I'm using the search engine correctly (Geocaching & the NGS websites) there are no AZ or RM within 1.4 miles of this Triangulation disk. Would they be that far away, or are they just not in the database? Or am I using the database incorrectly?

 

Doit2it, here is a tutorial on triangulation stations and the disks that go with them. Sometimes the reference marks and azimuth mark may have their own PID (thus separate datasheet). but most of the time they are only referred to on the datasheet for the triangulation station benchmark.

 

http://forums.Groundspeak.com/GC/index.php?showtopic=185361

 

If the USGS triangulation station has not been bluebooked (listed in the NGS database), then you are going to have to do some research to find the datasheet on it, and thus see if there were reference mark and azimuth mark disks set with it. You can contact the USGS, and tell them where it is, and they will find the datasheet in their file cabinet to send you a copy. Here is a link on how to contact them:

 

http://gallery.usgs.gov/audios/130

 

Usually a NGS triangulation station has a name stamped on it (like the property owner, town, etc), which I didn't see in your pic. I don't have enough experience with USGS triangulation stations to know if they use the same kind of guidelines or if a triangle on their disk means the same as the NGS..........or if they had to place a name on it to get bluebooked in the NGS database.

Edited March 12, 2011 by LSUFan

[AZcachemeister]

In any case, it looks like an awesome place to bring people to...whether by a waymark for the disk, a waymark for the observatory, or a Geocache (if the property owners are receptive).

[kayakbird]

No witness post, don't know what RM or AZ mean

 

The strange thing about this Benchmark disk is it is embedded in the porch of a building.

 

Doit2it,

 

Good, solid, somewhat public buildings are used a lot by the many setting agencies - can pick up a lot of history along the way.

 

Sorry about the abrev's - hope that you have had time to read through the links from LSuFan.

 

Through the magic of a GSAK filter it appears that there are 533 marks placed by the USGS in Tenn THAT HAVE PID's and nine of those are in Davidson County. Plotted the two closest ones on Google and plucked info from the 'View Original Datasheet' link on the 'Details for Benchmark: AA####'page.

 

9.7 miles ESE

 

GC0414_MARKER: DD = SURVEY DISK

GC0414_SETTING: 36 = BRIDGE

GC0414_STABILITY: B = PROBABLY HOLD POSITION/ELEVATION WELL

GC0414

GC0414 HISTORY - Date Condition Recov. By

GC0414 HISTORY - UNK MONUMENTED USGS

GC0414 HISTORY - 1952 GOOD NGS

 

8.4 miles WNW

 

GC0471_MARKER: Q = CHISELED SQUARE

GC0471_SETTING: 36 = BRIDGE

GC0471_STABILITY: B = PROBABLY HOLD POSITION/ELEVATION WELL

GC0471

GC0471 HISTORY - Date Condition Recov. By

GC0471 HISTORY - UNK MONUMENTED USGS

GC0471 HISTORY - 1948 GOOD NGS

 

A lot of us here salivate over chisel marks.

 

chisel mark thread

 

This is a favorite one of mine from a great road trip just over a year ago:

 

 

EV0852

 

HAPPY HUNTING, kayakbird

 

2114 12MAR11 EDIT

Edited March 13, 2011 by kayakbird

[Wintertime]

Through the magic of a GSAK filter it appears that there are 533 marks placed by the USGS in Tenn

But GSAK needs a database, so you're only talking about the USGS marks that are in the NGS database, right? "Doit2it" already searched the full NGS database (in addition to the older version on Gc.com), so as "LSUFan" noted, he'll need to contact USGS to find out about this one.

 

"Doit2it," I've found the USGS folks very helpful about this in the past, so don't hesitate to contact them. I think this is the best group to contact, but perhaps someone else here can confirm that:

 

National Geospatial Technical Information Center

 

Patty

[Papa-Bear-NYC]

Couple of things

 

1) The USGS (at least for this time frame) used the same disk blank for both Triangulation Stations and Bench Marks. The all say "Bench Mark" and they all have a triangle in the middle. The fact that there is an accurate elevation stamped on the disk tells me it's a bench mark, not a triangulation station. Furthermore, if it's on the front step of some structure, you can be absolutely certain it's not a triangulation station.

 

2) For any USGS triangulation station I've encountered (very few), I have NOT seen reference marks nor azimuth marks. The fact that they were set to make maps which, when done, were no longer needed, is probably the reason.

 

3) I have occasionally seen the USC&GS come along and use an existing USGS tri station disk for their own purposes, but they would generally resurvey it, and add their own Reference marks and maybe an azimuth mark.

 

Bottom line: without the backup information you can't tell what to expect and you shouldn't expect the USGS markers to follow the USC&GS rules.

Edited March 13, 2011 by Papa-Bear-NYC

[southpawaz]

I'm pretty certain that this would not be a triangulation station, despite the triangle in the center. A triangulation station would typically not have an elevation attached to it as stamped on this one, and being so close to the building would significantly affect the sight lines needed to triangulate its horizontal location. Most likely a bench mark disk, with accurately measured elevation but not location.

[+billwallace]

Here is a link to ScardyCat's Benchmark Viewer for Tennessee. Select the MyTopo map option, put your coordinates in the Location Search box, click Go! and zoom in. Looks like there is a triangle symbol there with an elevation next to it.

[+Doit2it]

Here is a link to ScardyCat's Benchmark Viewer for Tennessee. Select the MyTopo map option, put your coordinates in the Location Search box, click Go! and zoom in. Looks like there is a triangle symbol there with an elevation next to it.

 

Hmm, there is a triangle on the MyTopo option in the same location, but the elevation on the map is 1127 vs 1131 on the disk.

That would indicate that the info came from two different surveys, correct?

 

In any case, it looks like an awesome place to bring people to...whether by a waymark for the disk, a waymark for the observatory, or a Geocache (if the property owners are receptive).

 

Yes, they have an open house every month between March and November. That's when I noticed it, Friday night as I was walking out the front door. And a boy scout troop has put a geocache on the grounds, which I logged last fall. I'm going to another open house in August. I plan to ask the curators if there are any other benchmarks on the grounds.

Edited March 13, 2011 by Doit2it

[Wintertime]

I'm pretty certain that this would not be a triangulation station, despite the triangle in the center. A triangulation station would typically not have an elevation attached to it as stamped on this one

 

I don't know what's typical, but if you look at the triangulation station disk log I cited from my friend, you'll see an elevation stamped on it.

 

and being so close to the building would significantly affect the sight lines needed to triangulate its horizontal location.

True. However, I see from later postings that the topo map for the specified area does show a triangle at that location, so apparently this particular building-mounted disk is indeed a triangulation station.

[Wintertime]

Hmm, there is a triangle on the MyTopo option in the same location, but the elevation on the map is 1127 vs 1131 on the disk.

That would indicate that the info came from two different surveys, correct?

Or adjustments to the elevation since the mark was monumented. It's been 58 years!

 

If you looked at the Yosemite Point triangulation station I mentioned, the data sheet says 6939.5 feet, the stamping says 6935, and the topo map says 6936. But the mark has been there since 1905, so those are all referring to the same mark, not a reset. I'll bet the same is true of the one you spotted. Info from the USGS would confirm that for you.

[CallawayMT]

Hmm, there is a triangle on the MyTopo option in the same location, but the elevation on the map is 1127 vs 1131 on the disk.

That would indicate that the info came from two different surveys, correct?

Or adjustments to the elevation since the mark was monumented. It's been 58 years!

 

If you looked at the Yosemite Point triangulation station I mentioned, the data sheet says 6939.5 feet, the stamping says 6935, and the topo map says 6936. But the mark has been there since 1905, so those are all referring to the same mark, not a reset. I'll bet the same is true of the one you spotted. Info from the USGS would confirm that for you.

 

You are quite right; NGVD29 to NAVD88 datums. You are usually looking at 2-4' depending on your location. The other reason is that the level runs were adjusted after computations which could change the station elevations. That is why they stopped stamping the elevations on the monuments.

Edited March 13, 2011 by CallawayMT