Questionable Access

[+DNova]

I've read a bunch of datasheets for BM's in and near my zip code, and I have found a bunch of them that are on the roofs of buildings like hospitals and office buildings.

 

My question is: should I just forget about these BM's and assume I will not have the opportunity to find them, or do these places generally allow roof access for these purposes?

 

I understand that, especially now with a heightened (no pun intended) sense of security, building officials would probably not allow some random person access to their roof.

 

Has anyone had to deal with this at all? Let me know!

 

~Don

[+DustyJacket]

Most of the towers, antenna, water tanks, and rooftop benchmarks don't actually have a disk there.

(Unless the data sheet specifically mentions it.)

 

In most cases, the data sheet says the BM is: "the red light at the tp" or "is the roof peak" and so on.

 

You don't have to go up there, as long as you can see that point. I just shoot a photo from the ground.

 

DustyJacket

...If life was fair, a banana split would cure cancer.

[+Black Dog Trackers]

dustyjacket -

 

I think NovaNow really is talking about ones like this.

 

NovaNow -

 

I avoid all of them.

[zdv]

There are several in my area that are discs set into the top of elevator shafts on the roof of buildings. I guess whether or not you hunt these might boil down to why you hunt benchmarks.

 

I personally don't enjoy "access hassles" so I typically avoid marks that require permission to access, are in the curb in front of someone's house, on private land, etc. But if you enjoy the possibility of haggling your way to the BM then maybe it's for you..

[Z15]

I would avoid marks like this. Just going to look at it is not a good reason. Move on to something more public and avoid the hassels.

[rusty0101]

... on private property. If you do not feel comfortable asking the property owner for access, don't try to recover the mark. We are not BASE jumpers.

 

Additionally, the people in larger buildings, who can physically provide access, are rarely the people who can make the decision to provide that same access.

 

If you are interested in getting to some of these marks, I would recomend contacting property management for the building. If the building has a Conciearg, this person may be able to provide you the contact information. If the building has a security desk at the entrance, it is likely that finding out who to contact will be harder.

 

If the NGS data sheet does not have a point of contact for the building, that is a reasonable enough explanation for people to provide an update to the NGS.

 

If all you are going to do with your benchmark recovery is log it here, then I agree with the notes earlier that these marks probably are not worth the trouble.

 

As a rule the surveyors working in an area with buildings that have benchmarks affixed to their roof (as opposed to a flagpole or spire being the mark itself) will have their own set of data and contact information for these marks.

 

That said, if a mark has not been recovered for a couple of decades, it is reasonable to expect that some of the contact information has changed, that the roof has been re-surfaced, and that there may be other changes that make it a good idea to collect what information you can to update the NGS datasheet.

 

If for some reason a survey crew who is not from the area needs to use that mark, the updated contact information on it's own may save the surveyor several hours or even days of independent research to collect that same information.

 

Then again, that's just my opinion. As has been noted elsewhere, with modern surveying methods, and current GPS tools, it is likely that in the future there will be much less of a need to occupy any one specific point. A large building, with visability for miles around is quite nice, but hardly required.

 

-Rusty

[survey tech]

Rusty is right that these points often involve major hassles. Many times surveyors even have considerable difficulty getting access to them.