Notifications
Clear all

Rehabilitating the "Pin Cushion"

9 Posts
6 Users
0 Reactions
4 Views
(@kent-mcmillan)
Posts: 11419
Topic starter
 

I thought I might be in PLSSia for a fleeting moment today. It was when I found these two iron rods (steel rebars for the finicky) both supposedly marking the same corner.

The 5/8-inch bar (leaning about 30deg off plumb) was visible on the surface. The bent over 1/2-inch bar was below the surface. About ten years ago this corner was described as marked by "two 1/2-inch iron rods found driven side by side at elevation 678.55". Obviously, sometime in the last ten years someone (probably a surveyor) beat one of the two rods over so that no one would ever find it (unless they used a shovel).

The fact that one bar is a #5 and the other a #4 is a minor detail. The real question is which is an original corner. Both appear to be more than 20 years old. My preliminary idea is that the #5 (which didn't get beaten over) probably isn't the orginal corner, that the #4 bar (which did) is.

The bottom 7 inches of the #4 bar were straight and fairly plumb. The bar had been driven into a stiff, weathered limestone soil, so when it was apparently beaten over with a sledge, the lower 7 inches were held in place by the soil even as the top was bent way over.

So, there really wasn't anything to be done but to straighten out the severely bent #4 bar and get a location on it afterwards. It was 0.07 ft. away from the top of the #5 after straightening.

 
Posted : December 20, 2012 11:43 pm
(@kevin-samuel)
Posts: 1043
 

Surveying 101!

The rebar with the most flagging when found is the corner! 😉

 
Posted : December 21, 2012 5:59 am
(@alan-cook)
Posts: 405
 

> So, there really wasn't anything to be done but to straighten out the severely bent #4 bar and get a location on it afterwards. It was 0.07 ft. away from the top of the #5 after straightening.

I see the center punch is not only still in your bag, but has a fairly sharp point on it.

 
Posted : December 21, 2012 6:02 am
(@kent-mcmillan)
Posts: 11419
Topic starter
 

> I see the center punch is not only still in your bag, but has a fairly sharp point on it.

Yes, the center punch is a very good tool. I got ties to those rods from two different control points and the punchmark meant that the prism rod could be set up and centered on the exact same point (subject only to the very small plumbing error of the pole) for each tie.

 
Posted : December 21, 2012 7:03 am
(@adamsurveyor)
Posts: 1487
 

Maybe someone beat the bar over so that the top was at the true location....;-)

But seriously, I don't know why you would beat the bar over. It seems like if you wanted to obliterate the confusion you would remove it, otherwise why not leave it right where you found it? It's already there if some other surveyor comes along and likes it best....and they don't have to straighten it up.

 
Posted : December 21, 2012 1:56 pm
(@derek-g-graham-ols-olip)
Posts: 2060
Registered
 

Kent-

Who sez that a point cannot be about 5" in diameter ?

Gives room for diurnal temperature change !

Happy Holidays to you and SWMBO !

Alex and Derek

 
Posted : December 21, 2012 2:30 pm
(@dave-karoly)
Posts: 12001
 

Wow how much do the rebars shrink in the cold up there in super-latitudinal America?

 
Posted : December 21, 2012 4:28 pm
(@dave-karoly)
Posts: 12001
 

What no vise grips in the truck this time?

 
Posted : December 21, 2012 4:29 pm
(@kent-mcmillan)
Posts: 11419
Topic starter
 

> What no vise grips in the truck this time?

Yes, I always carry a pair of vise grip pliers. I rehabbed that pair of rods just to get a good tie to the bent over one. The jury is still out on which one is the original corner, but the #4 bar is the leading contender. There is a series of four corners with about the same configuration of two markers less than 0.10 ft. apart. I'm looking at the whole series and I pretty much have to be able to say what accounts for the clusterfuge and have definite evidence supporting one of each pair before pulling the other. Considering the setting, it is nearly impossible that the second bar wasn't set in full knowledge that another bar was already in place less than 0.10 ft. away.

 
Posted : December 21, 2012 6:37 pm