Lat, Long BLM Plat

I see that on their modern plats. They tie to a hard corner with lat & long. The corner can be any corner though.

I had one a couple years ago. My OPUS was within a couple tenths of a foot so yeah, it's excellent info when doing a retracement survey. If all surveys were done as good as the BLM we'd be in tall timber!

> How did I screw that up!

haha...that's the first thing I assume too. I thought everyone else asked how someone else screwed that up. Not me, I always go 'how did MightyMoe screw that up'? 😉

Not 12", => 21 seconds....did you get a number switched? Those can be hard to spot.

That's what I thought at first. But for once I entered the starting point with the correct numbers. Then I figured I had the Quad misplaced in my drawing. Then I figured something was off with my setup in TGO.

I finally just looked at the Quad and if you plot the lat it's two miles north of the SE township corner. Then I went to Google and put in the section lines and the lat long hits pretty close to the NE of Section 25.

When I read the notes they start off by declaring that the lat. long. was determined for the SE corner of the township by GPS and they use the same number that's on the plat.

Surveyed 1994-1995.

I still think I'm missing something simple; but for now I'm shifting all the points two miles south in TGO and reimporting them into the drawing.

Probably just a mistake; did not compute it to the SE corner?

Yeah, I figure that it's a drafting error. I THINK it's the NE of 25. But I'll figure it out later this week.

So far I've never come across anything like it; they always have worked before.

And there aren't any resurveyed townships adjoining it so I've got no check for it.

GCDB

Did you check GCDB?

BUT-BUT-BUT what about protecting the Plat!

😛

ok- I'll stop now......

Two miles should be about 2 minutes (very roughly).

Might help in chasing it down.

I had to learn these general conversions recently when for some reason, Corpscon threw me a curve and had me 2 degrees off which is about 140 miles. Oops.....

GCDB

Yeah, the lat long kind of fits the GCDB lines at the northeast corner of Section 25.

In this part of the world the GCDB isn't accurate very often-to put it kindly.

Sometimes up to 1500' off. That's unusual, but 100-300' isn't.

So it's the last number I will look at. The lat long at the township corner is usually the best number. Then I calculate true north through the township and will get very close in the field.

I expect to be within 5 feet by doing it that way which makes corner location really fast in these new areas.

1 second of latitude=+-100', one minute=+-6000', 2 minutes=+-12,000'.

That was my first thought also, but the calc corners hit right on top of corners two miles north of where I was trying to be which doesn't work well with the 2 minute shift.

When I talked to Mike L with the BLM during that era 94-96...he was always trying to do static on the SE corner of the townships....maybe he did it at the NE 25 and typed in the wrong corner in his notes out of habit...how does the terrain look, is it hard to get into the se of sec. 36?

Pablo

> 1 second of latitude=+-100', one minute=+-6000', 2 minutes=+-12,000'.
>
> That was my first thought also, but the calc corners hit right on top of corners two miles north of where I was trying to be which doesn't work well with the 2 minute shift.

actually that works best with the Nautical Mile: about one minute of arc of latitude measured along any meridian, or about one minute of arc of longitude at the equator. By international agreement it is 1,852 metres (approximately 6,076 feet)... but I remember those terms more easily than some.

Nah! Road goes right by it. Flat as can be.

Not sure what happened to the GPS data, but it sure is "out".

It is really odd; never seen it before. And I've used dozens of these plats.

But I think I have it correctly "moved". We'll see by Friday.

gotta love numbers sometimes

Cir of the earth= +-24860 miles (rounding off) or 131,260,000ft./1,296,000 seconds of arc(seconds in a circle)=101ft.

A really convenient number when working with latitudes; 0ne second=100', tenth of a second=10', ect.

I really hate decimal degrees-I just can't tell how far apart anything is.

Would you be willing to supply a link to the plat or the township involved.

- jerry

6th pm 40n 64w

MOE...

I may have missed it, but I don't see anything in this thread about contacting your BLM office? Seems to me this would be Step 1...

MOE...

I'll mention it to one of the guys next time I see him, we are working on an ongoing survey.

But, this isn't a big deal, it's more about much trust I should put on data that is ancillary information.

The first thing I did was enter the coordinates into my database and start calculating. That was my mistake. I should have checked the position before starting.

I STILL think I'm missing something......

I've got that nagging feeling.....

Payback....

> Calculated Section Corners (Land Surveying)
>
> by MightyMoe, Friday, September 21, 2012, 14:25 (19 days ago)
>
> 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 against the calculated corners.
>
> Found: 20,566.11
>
> Calculated: 20,566.21

Sometimes it works, sometimes it don't. 😉