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Encased in PVC Pipe?

 
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msrubble
Geocacher


Joined: 23 Jul 2006

Posts: 148

PostPosted: Mon Oct 02, 2006 8:02 pm    Post subject: Encased in PVC Pipe? Reply with quote

This seems to be a MnDOT thing, so I thought I would ask here rather than at groundspeak.

Sometimes the description of a MnDOT mark has a note at the end saying something like, "The rod is encased in a 6-inch PVC plastic pipe that is flush with the ground surface."

Does this mean:

  1. The pipe is conformed to the rod.
  2. The pipe is conformed to the rod, and the disk is covered.
  3. The rod is driven approximately in the center of a pipe.


I have not yet found any benchmarks that MnDOT or the NGS describes as being encased in a PVC pipe. I have found two that are approximately centered in PVC pipes. It's worth a mention in the description if option C is what they mean by "encased." One of them you can spot from across the street.
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Pear Head
Past MnGCA President


Joined: 04 Apr 2004

Posts: 5708

PostPosted: Mon Oct 02, 2006 8:15 pm    Post subject: Reply with quote

I believe it's c.

I'd ask on the gc.com forums - there are some very smart folks over there when it comes to this kind of thing.
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Marsha and Silent Bob
Past MnGCA President


Joined: 02 Sep 2003

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PostPosted: Mon Oct 02, 2006 11:29 pm    Post subject: Reply with quote

http://www.geocaching.com/mark/log.aspx?LUID=81421938-333a-4713-a795-89a281719e6e
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jrest
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Joined: 11 Jun 2005

Posts: 392

PostPosted: Tue Oct 03, 2006 7:55 am    Post subject: Reply with quote

Here is one with the lid open... http://www.geocaching.com/mark/details.aspx?PID=AB9953

http://img.geocaching.com/benchmark/lg/2a30128a-c277-4d90-b9e5-1cda96af3090.jpg
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EskoClimber
Past MnGCA President


Joined: 24 May 2005

Posts: 815

PostPosted: Wed Oct 11, 2006 8:25 pm    Post subject: Reply with quote

It is common for MnDOT to sleeve the top 18-36 inches of the rod in a PVC pipe just to protect it from the enviroment. The usually do that when the BM is in soft ground. The problem is that new statiions are made of aluminum where the older ones are made from steel. The end cap is usually a screw in and often requires a pipe wrench to open.
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msrubble
Geocacher


Joined: 23 Jul 2006

Posts: 148

PostPosted: Fri Oct 13, 2006 10:23 pm    Post subject: Reply with quote

Here's the one you can see from the other side of the road. CHAP RM 2.

Yes, I know, I should have put metric before standard. Oops.

No lid. Just a 4-inch standard MnDOT RM disk. The other one I've found like that is ABA RM 2.

No photos yet, but may have eye-level views and area views soon.
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EskoClimber
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Joined: 24 May 2005

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PostPosted: Sat Oct 14, 2006 2:35 pm    Post subject: Reply with quote

What you've found are Reference Marks, sometimes you can log them, but usually not. The RMs will have arrows pointing at the actual station. The station usually has a triangle with a dot in the center.
You can log the reference mark in this case using the Point ID QP1899.
Have you found CHAP NO.1?

As far as ABA goes, have you found the other two marks there (ABA RM1 & ABA)?
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msrubble
Geocacher


Joined: 23 Jul 2006

Posts: 148

PostPosted: Sat Oct 14, 2006 10:21 pm    Post subject: Reply with quote

EskoClimber wrote:
What you've found are Reference Marks


I know that.

Quote:
Have you found CHAP NO.1?


No. I can see another witness post directly across the street from CHAP RM 2. I think it's for CHAP RM 1. I poked around a little with my boot but didn't find anything right off. I don't have a metal detector. It's supposedly flush with the ground.

Quote:
have you found the other two marks there (ABA RM1 & ABA)


Yes and no. ABA RM 1 is in poor condition. Rod bent, most of disk missing, arrow pointing the wrong way. The station ABA itself is supposedly flush with the ground, but if I have measured it right, it's at the edge of a gravel driveway and so may be under dirt and gravel that's been packed down tight by cars and trucks driving over it. The description can't be right, because RM2 is the more westerly of the two reference marks, and the NGS says ABA is southwest of RM 2 and southeast of RM 1.

I think I am going to have to resurrect my ancient camera for benchmarking.
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EskoClimber
Past MnGCA President


Joined: 24 May 2005

Posts: 815

PostPosted: Sun Oct 15, 2006 9:17 am    Post subject: Reply with quote

Sorry about the obvious statement about RMs. You'd be surprised how many people think those are the stations. The other one that people think are stations are azimuth marks.
The description could very well be wrong, happens all the time. I've found many marks on bridges that were described as being in the SW corner and turned out to be somewhere else. Same thing with your SW SE when it should be something else (SE SW or SW and more SW).
The station many times is flush with the ground to protect it. The problem is that the station very often gets covered by grass growing over it or by "slumping". If it has been covered or buried you might never find it without a metal detector and shovel. You can see what happened to RM1. Probably nicked with a lawm mower or snow plow.
The other common thing is to cover the station with a rock. I don't think I've ever seen that in an urban setting but I've see it many times in the boondocks.
The last thing I'll mention is the difference between "scaled" and "adjusted". Scaled means the lat/long were picked off a map and subject to considerable error. Adjusted means the lat/long is dead on the money. You probably know that already.
I use my old digital 1.3mp camera for this little chore, works great.
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msrubble
Geocacher


Joined: 23 Jul 2006

Posts: 148

PostPosted: Mon Oct 16, 2006 11:35 pm    Post subject: Reply with quote

I've posted photos of ABA RM 2 and CHAP RM 2. Would you call that "encased"?
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EskoClimber
Past MnGCA President


Joined: 24 May 2005

Posts: 815

PostPosted: Sat Oct 21, 2006 3:48 pm    Post subject: Reply with quote

Yep, thats what they call encased. Sometimes they put a screw on PVC cap on the PVC, then you might need a pipe wrench.
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