Jump to content
Sign in to follow this  
Followers 1
k5knt

CB132: Is it or isn't it?

Recommended Posts

EDIT: I just noticed I left out the "0" in the post title... It should be CB0132

 

2076109200039870333dUxgAt_th.jpg

 

CB0132_U.S. NATIONAL GRID SPATIAL ADDRESS: 14RLV623813(NAD 83)

CB0132_MARKER: DD = SURVEY DISK

CB0132_SETTING: 36 = SET IN A MASSIVE STRUCTURE

CB0132_SP_SET: BALUSTRADE

CB0132_STAMPING: 1844.015

CB0132_STABILITY: B = PROBABLY HOLD POSITION/ELEVATION WELL

CB0132_SATELLITE: THE SITE LOCATION WAS REPORTED AS SUITABLE FOR

CB0132+SATELLITE: SATELLITE OBSERVATIONS - November 27, 2003

Ok, The location for this benchmark seems to be correct, although my GPSr was putting it on the other side of the bridge. This bridge has a plaque that identifies it at the Pat Murphy Bridge. As you can see in the photo, there is no stamping of 1844.015.

 

CB0132'DESCRIBED BY NATIONAL GEODETIC SURVEY 1933

CB0132'IN SAN ANGELO.

CB0132'AT SAN ANGELO, TOM GREEN COUNTY, 0.7 MILE WEST OF THE COURTHOUSE, AT

CB0132'THE PAT MURPHY BRIDGE, NEAR THE MIDDLE OF THE BRIDGE, AND IN THE TOP

CB0132'OF THE BALUSTRADE. A UNITED STATES GEOLOGICAL SURVEY STANDARD DISK,

CB0132'STAMPED 1844.015 AND SET VERTICALLY.

 

This is in the top of the balustrade, but I would say it was set horizontally. What am I missing?

 

Kent

Edited by k5knt

Share this post


Link to post

I'll take a stab at this, I'm sure others will have further comments. FIrst, the fact that it is scaled means that you should not depend on the coordinates to lead you directly to the mark. It may be off by as much as 1 second in latitude and/or longitude or 660 feet. So, follow the directions, which is what you did. However, the stamping and mounted vertically are more worrisome. I tried to blow up your picture and there seems to be a smudge on the left side of the disk. Could something have been stamped there, possibly in front of the word "feet"? The numbers in the stamping match the elevation at the time the disk was placed. May bench marks, i.e. an elevation markers, are mounted vertically but by no means all of them. I'm not sure what to make of that problem.

Share this post


Link to post

I didn't notice the "smudge" until I looked at the photograph in my computer at home. I will try to return this next week and take a closer look. Looking at a higher resolution photo, it seems that there is something smeared on the disk. If this is the case, should I try to scrape it off?

 

Kent

Share this post


Link to post

I have run across at least one disk without the described stamping.

Location is scaled. This generally means that it could be off by (as rogbarn noted 660 feet). The description does not state on which side of the bridge set. The desription does say 'on top of the balustrade'. That would be a horizontal setting, not a vertical setting. In 2003, the Power Squadron listed it as 'suitable for satellite'. Well, it was the Power Squadron, but a vertical setting is not suitable for satellite observation. It would seem that they found the same disk as you did.

On the other hand, I doubt that I would claim that I found it, without the stamping. How do I know that this is the right disk? I've been to more than one bridge with several disks. Two I found, one I didn't. ( I really wanted to find the US Harbor Lines Disk! But they all seem to have disappeared. :D )

Share this post


Link to post

Multiple disks occur on the same bridge often enough to make us cautious, but often they are placed by different agencies. I would think it would be highly unusual for the USGS to place two disks on the same bridge, so I would guess that you found the right disk. Rogbarn is correct in pointing out that the stamping would be the elevation, which appears to be damaged or obscured by something. The "set vertically" might just be a mistake.

 

If it was near the middle of the bridge on the balustrade, and if you also looked at the other balustrade and searched throroughly for a vertically mounted disk, but didn't find one, then you can be more confident. The GPS coordinates for this station have no relevance for identifying the disk, other than perhaps helping you locate the bridge itself.

 

Does the bridge plaque indicate a construction date? If the bridge hasn't been replaced or repaired since 1933, you have even stronger evidence that you found the right disk.

Share this post


Link to post

I've uploaded a hi-res closeup of the disk

here. It looks to me that something has been put on the disk to cover the elevation. Notice how the substance appears to have been removed from around the lettering. Is it possible that the elevation was discovered to be incorrect and covered with something? The idea, being to come back later and re-stamp with the correct elevation? How accurate can I expect my GPSr's elevation reading to be (I have a Garmin GPSmap 60c)? Could I check the elevation with that?

 

I will check the plaque for a build date when I go back. I'm also going to look for any evidence of another disk on both sides of the bridge.

 

Kent

Share this post


Link to post

Another discrepancy:

DESIGNATION - 1844.134

STAMPED 1844.015

Superceded 1844.02

 

You would think that the designation and stamping would use the same elevation. That which was supposed to be stamped is close enough to the superceded value.

 

I'd be willing to assume one discrepancy (setting transcribed vertical when it wasn't, or stamping written down and not actually stamped) if a lot of other things check out, but you don't have enough things checking out to support that.

 

I'd say the decision rests mostly on what you can learn of the history of this bridge. It is entirely possible there was a stamped disk there, but the bridge has been refurbished and that disk lost in the process. USGS may have set a new disk in the reconstructed bridge at a similar place and similar elevation, but not gotten around to stamping it.

Share this post


Link to post

It sure does look like something used to be inscribed before the "FEET". Something is not right, somehow. I have had luck in the past checking the county (in my case Orange County, CA) records. Many are now on line. Check your county's website, in logical departments (your results may vary!)

 

Also, notice the disk was set by USGS, although first described by NGS. More chances for errors. This is one DaveD might help out by looking for something in the USGS files he sometimes has access to. Interesting issue. A really good question is the age of the bridge there now. Is it older than 1933?

Share this post


Link to post

I revisited the bridge this morning and discovered the following:

 

The J.G. (Pat) Murphy Bridge was built in 1922. It was widened in 1951 by the Texas Highway Department. The bridge is part of Beauregard Avenue and crosses the North Concho River. Traffic flow is in an East-West Direction.

 

The mark is on the north side of the bridge, twelve balustrades east from the west end of the bridge. It is directly over the river. It is mounted on the top of the balustrade and is set horizontally. The elevation stamping has been ground off. My hand held GPSr gave the coordinates of : N 31° 27.521', W 100° 26.970'. The elevation reading continually fluctuated between 1835 and 1847 feet.

 

There has been some repair work done to the guard railing just east of the disk.

 

After walking both sides of the bridge, I was unable to locate any other disks.

 

I will send Deb and email with this information and photographs to see how this should be logged with NGS. I have made a note on the log here at GC.

 

 

 

Kent

Share this post


Link to post

I received a reply from Deb this morning. She suspects the disk is a reset that wasn't reported to the NGS. She also said that she was going to send it to Burt Smith, who would make the determination on what to do with this mark. She asked him to contact me directly.

 

Anyone know who Burt Smith is?

 

Kent

Share this post


Link to post

I received a reply from Deb this morning. She suspects the disk is a reset that wasn't reported to the NGS. She also said that she was going to send it to Burt Smith, who would make the determination on what to do with this mark. She asked him to contact me directly.

 

Anyone know who Burt Smith is?

 

Kent

 

Apparently one of the NGS personnel who deals with Mark recovery and maintenance at their headquarters.

 

Mark Recover B. Smithhttp://www.ngs.noaa.gov/INFO/OnePagers/Online_Mark_Recovery.pdf

 

- jlw

Share this post


Link to post

I finally received a reply from Mr. Burt Smith, here is what he had to say.

Kent:

 

I can't find anything to justify the errors that you found. I looked for the original description, but we no longer have that quad available to us. The only thing that makes sense is a reset by persons unknown!

 

Regards,

 

Burt

Share this post


Link to post

Hi all,

 

I've been away from the hobby for awhile and this one is still bugging me... :D

 

I am currently in Utah visiting family and I showed this to my father-in-law who is a retired surveyor. He noticed that the disk in question (pictured below) is a triangulation station while the data sheet lists it as a survey disk.

7cece961-109d-4444-952a-480c63ed3a44.jpg

The mark is on the north side of the Pat Murphy Bridge, twelve balustrades east from the west end of the bridge. It is directly over the river. It is mounted on the top of the balustrade and is set horizontally. The elevation stamping has been ground off. My hand held GPSr gave the coordinates of: N 31° 27.521', W 100° 26.970'.

e2ed496b-5c6a-4af7-8e08-807bf4fdd1b0.jpg

Close up of the disk.

 

From the NGS Data Sheet.

ATABASE = ,PROGRAM = datasheet, VERSION = 7.61

1 National Geodetic Survey, Retrieval Date = JUNE 11, 2008

CB0132 ***********************************************************************

CB0132 DESIGNATION - 1844.134

CB0132 PID - CB0132

CB0132 STATE/COUNTY- TX/TOM GREEN

CB0132 USGS QUAD - SAN ANGELO SOUTH (1978)

...

CB0132

CB0132_U.S. NATIONAL GRID SPATIAL ADDRESS: 14RLV623813(NAD 83)

CB0132_MARKER: DD = SURVEY DISK

CB0132_SETTING: 36 = SET IN A MASSIVE STRUCTURE

CB0132_SP_SET: BALUSTRADE

CB0132_STAMPING: 1844.015

CB0132_STABILITY: B = PROBABLY HOLD POSITION/ELEVATION WELL

CB0132_SATELLITE: THE SITE LOCATION WAS REPORTED AS SUITABLE FOR

CB0132+SATELLITE: SATELLITE OBSERVATIONS - November 27, 2003

CB0132

CB0132 HISTORY - Date Condition Report By

CB0132 HISTORY - UNK MONUMENTED USGS

CB0132 HISTORY - 1933 GOOD NGS

CB0132 HISTORY - 1935 GOOD NGS

CB0132 HISTORY - 20031127 GOOD USPSQD

CB0132

CB0132 STATION DESCRIPTION

CB0132

CB0132'DESCRIBED BY NATIONAL GEODETIC SURVEY 1933

CB0132'IN SAN ANGELO.

CB0132'AT SAN ANGELO, TOM GREEN COUNTY, 0.7 MILE WEST OF THE COURTHOUSE, AT

CB0132'THE PAT MURPHY BRIDGE, NEAR THE MIDDLE OF THE BRIDGE, AND IN THE TOP

CB0132'OF THE BALUSTRADE. A UNITED STATES GEOLOGICAL SURVEY STANDARD DISK,

CB0132'STAMPED 1844.015 AND SET VERTICALLY.

CB0132

CB0132 STATION RECOVERY (1935)

CB0132

CB0132'RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 1935

CB0132'RECOVERED IN GOOD CONDITION.

CB0132

CB0132 STATION RECOVERY (2003)

CB0132

CB0132'RECOVERY NOTE BY US POWER SQUADRON 2003 (CAG)

CB0132'RECOVERED IN GOOD CONDITION.

 

 

Any new thoughts or suggestions?

 

Thanks,

 

Kent

Share this post


Link to post

Two things going for you:

 

1) The NGS call disks set by other agencies "Survey Disk" where for their own disks they would call them "Tiangulation Station", "Bench mark", etc. Since it is a USGS disk, that is probably why it's called a "Survey Disk"

 

2) I've noticed most USGS disks have a triangle in the center, even when they are not triangulation stations. Essentially they had a "one size fits all" mentality with their disks. Since this was supposed to be set vertically and had an elevation stamped on it, it must have been a Bench mark (not a triangulation station) but it still may have had the triangle.

 

But:

 

1) you say it's mounted horizontally (datasheet says vertically) and it seems to be unstamped (datasheet says "1844.015"), so I'd say it's NOT the disk described in the datasheet. Since it was recovered fairly recently (although USPSQD has been know to make mistakes) and the bridge does not appear to have been renovated, I'd say the mark is there on another balustrade. I assume when you say directly over the water, you were in the "middle" of the bridge. Did you look on the other side of the bridge?

Edited by Papa-Bear-NYC

Share this post


Link to post

1) you say it's mounted horizontally (datasheet says vertically) and it seems to be unstamped (datasheet says "1844.015"), so I'd say it's NOT the disk described in the datasheet. Since it was recovered fairly recently (although USPSQD has been know to make mistakes) and the bridge does not appear to have been renovated, I'd say the mark is there on another balustrade. I assume when you say directly over the water, you were in the "middle" of the bridge. Did you look on the other side of the bridge?

 

Maybe the horizontal / vertical descriptions are causing confusion? The datasheet also says that the disk is mounted "in the top of the balustrade". The disk is mounted on the top of the "horizontal surface" i.e. you could place an item on top of the disk. To me, mounted vertically would indicate that the disk would be on the vertical surface and anything placed on the disk would fall to the walkway.

 

I can't remember if I was in the exact "middle" of the bridge or not, but there was water (the river) under the location on both sides. I've walked both sides of the bridge several times before I even spotted the mark. This is the only one I could locate. Here is some more information on the bridge:

 

The J.G. (Pat) Murphy Bridge was built in 1922. It was widened in 1951 by the Texas Highway Department. The bridge is part of Beauregard Avenue and crosses the North Concho River. Traffic flow is in an East-West Direction.

 

There has been some repair work done to the guard railing just east of the disk. Date of this repair is unknown.

Share this post


Link to post

k5knt

 

After reading all you wrote I believe that you have found the correct mark for this

PID. The apparent conflict in the description between "top of the balustrade" and "set vertically" can be explained as confusion on the part of the original scrivenor.

 

CB0132''AT SAN ANGELO, TOM GREEN COUNTY, 0.7 MILE WEST OF THE COURTHOUSE, AT

CB0132''THE PAT MURPHY BRIDGE, NEAR THE MIDDLE OF THE BRIDGE, AND IN THE TOP

CB0132''OF THE BALUSTRADE. A UNITED STATES GEOLOGICAL SURVEY STANDARD DISK,

CB0132''STAMPED 1844.015 AND SET VERTICALLY.

 

I have posted in the past that even though the accepted standard for the term "set vertically" means a disk in the side of structure, rather than on top, it can also be construed in terms of the orientation of the stem of the tablet; ie: you would have to drill vertically to set a tablet on top of the balustrade, while you would be drilling horizontally to set one on the side.

 

The missing stamping might be explained by this note near the top of the datasheet:

 

CB0132.WARNING-Repeat measurements at this control monument indicate possible

CB0132.vertical movement.

 

This would also account for the differences between the designation, the reported stamped elevation, and the superceded elevation. Faced with these discrepancies, it would not surprise me that some agency might grind off the misleading stamping.

 

Since you have searched over the entire bridge with no additional finds, and this disk fits the datasheet description in every other regard, I would conclude that this is indeed the mark described, and would be confident in reporting it as found.

 

That being said, as a surveyor I would certainly hesitate to use this mark for any work requiring better than one foot accuracy.

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  
Followers 1

×
×
  • Create New...