I need to calculate a 6 Section area for some corner searches. I had located the northeast and southwest corners six years before in different projects....so I get the plat out and start "drawing" the Sections in autocad.
1914 plat with brass caps. I calculate the area without applying any convergence and get a nice rectangle. Mutiply by 66 and inverse the found agaisnt the calculated corners.
Found: 20,566.11
Calculated: 20,566.21
OK what did I do wrong?
Start looking-can't find any mistakes.
Oh well; I guess I'll see when I get out there.
The chances of these corners fitting this well are about 0, but....
Somehow I would feel better about it if there were 10-20 feet of difference; guess I'm jaded.
That's a big problem with surveyors. We hate it when things add up perfectly. We know we must have done something wrong, somewhere, someway. No half mile is precisely 2640.00 feet and neither is the next one. No angle is really, truly 90.000000. It simply can not happen. The odds are astronomically against it.
Not only that, but it wouldn't even be fun anymore... if everything fit!
Might as well just hang it up.;-)
Make sure and mark the secondary one as being 0.09 S X 0.04 W of the true corner on your plat, so the property owner can figure it the correct position......
I'll set new ones at my calcs. That way they will finally be correct!
Some are long some are short, once in awhile it should just hit right on.
About ten years ago was doing a survey in the Utah mountains following a very good deputy from 1898. We had found corners and from them was finding them about everywhere. I had two section corners and had calc'd the midpoint and my partner went to look. He called me on the radio and said he found the corner. He had gone to the search coordinate, zeroed in and pushed the pole into the dirt. About an inch down it clunked. Dug down around and there was the quarter stone big as life. We found several others by digging about a two foot wide area no longer than 10 feet (stones in this forest tended to become buried over the years).
Most of the retracements I've done following about 1913 when they started using brass caps are quite good with about 5 feet being a long distance off from the record, maybe 2 feet being more in the range. So I'd expect to hit one right on every once in awhile. I found one about 30 feet off and truly believed it had been moved. The feds had already accepted it in a retracement and it actually benefited the private owners so I let it alone (would have been an uphill battle to prove it was moved, all there was was the measurement to go on) but every other marker we found doing that survey was within 2 feet of the record.
I just did one where I came within 0.16' of a 1970 survey by a local guy who is long gone (but well respected by the "old timers"). Every time I've followed in his footsteps, it's been an easy walk. He was a WWII U-boat captain in the German Navy. From what I've been told by a mentor, he was a really nice guy.
Its driven more than one surveyor to drink... or fishing!
Related Question
I was playing with a free add-on to Google Earth.
It's PLSS in Google Earth (PLSGE)
from Metzger + Willard, Inc.
http://www.metzgerwillard.us/EarthSurvey.html
Apparently it connects to the BLM and returns/displays Secton Corner values.
How are these derived?
Fom records? From calculations? Guesstimates?
What accuracy would be expectd?
Thanks
In the western states the BLM makes a least square adjustment of the GLO data, modern record data, and GPS coordinates, to come up with the coordinates. Some are spot on, some are estimates ...they have a name for it, GCDB I think.
You da man. Used GCDB in Google and found this
http://www.blm.gov/wo/st/en/prog/more/gcdb.html
it 'splains it all
Thanks
Apparently it connects to the BLM and returns/displays Secton Corner values.
How are these derived?
Fom records? From calculations? Guesstimates?
What accuracy would be expectd?
In places it's "OK". By OK +-50'. After that it gets worse. From what I understand even the brand new surveys put into the GCDB are not going in using the new lat, long coordinates. They are getting new values an a few corners and then the old plat is "least squared" adjusted to finish the figure.
What value a "least squared" adjustment would produce in that situation is I have know idea. But, I could be wrong about that-it was a comment from another surveyor-not offical.
I only use it just to get a rough Idea of where I am and nothing more. There is usually much better info out there.
this is an example of the section lines plotted on google and the actual corners found on the ground plotted on google:
Shoot-the photo didn't come through-one more time:
The two stones are shown with the point# the north one is the NW corner of section 16 and the south is the W1/4. They are a bit over 150' from the GCDB lines. That isn't unusual. Many areas are closer than this and some are farther off. It's a nice feature to be able to use.....but, it's far from a real database of corners at this point.
