This survey has me a little confused, so hopefully someone can help me figure out the stated compass variations. It appears that the surveyor is describing the north south lines as being both 12°30'E and 10°30'W.
One plat, 2 brg systems. He reset the declination, when the 1st declination did not fit so good, on the other part of the job!
N
The W may be a scrivener's error, since the values in that area and era were probably all east.
Would two different dates (original gov't survey vs resurvey) explain about 2 degrees change?
Edit: I see that the whole image did not load for me the first time, so I need to digest the text.
There are places where it is possible to have different declinations due to local attraction...........something to consider?
I think he's showing a 23 degree angle. That's not the way I'm used to thinking about the magnetic variation, but it might fit. Now, what does defrosting glass mean? I must be reading that wrong.
Use the mean! That'll be close enough.
Sorry........I mis-read them as if both in the same quadrant. Oooops......
Doubtful you'd get THAT MUCH declination locally.
But, in conjunction with a scrivener's error......maybe two or three degrees might look a bit more reasonable.
"defrosting glass" How about "depositing glass"?
I think he might mean that the north-south section lines above the bottom tier of sections are va. 12°30'E and the bottom tier of sections (31-36) are va. 10°30'W. The text about glass is "depositing glass in mound".
Did the original surveys in this township not include all the sections, and get finished by someone else? Was there some Indian boundary or other discontinuity just north of the lower tier of sections? That is the only way it would make sense to have such extreme difference.
> I think he might mean that the north-south section lines above the bottom tier of sections are va. 12°30'E and the bottom tier of sections (31-36) are va. 10°30'W.
Yes, that's exactly how I understood the portion of the note that reads:
>All N and S subdivision lines are run on 12°30'E excepting the lines between the south sections on the town line. These are 10°30'W N and S owing to the fact that the subdivision corners are 34-45/100 chains further East than the corresponding corners on the South and N Town lines
That's it. Doh!
He seems to have retraced and run a line that holds the subdivision corners on the south township line per plan, but holds the corresponding northerly section corners per field note calls as 34.45 chains east of where they would be by plan. The line run is 87.44 chains with an included angle of 23-12-10 (the difference in variances within 0-12-10).
Just as background, it should be noted that a common way of using a compass to run lines was to run a trial (blank) line from one corner to the vicinity of the other, measure the falling (miss), and calculate the variation that should have been set off in the compass to hit the corner. Then the line was run backwards on the corrected variation, marking trees (if any) on the way. That 23° difference in variation is an extreme example of the principle, although the 10°30'W variation was probably calculated from other information already at hand rather than being a measured falling on a trial line.
I think that Kent has it.
It was thought that the original surveyor in 1882 didn't establish any original corners inside the township. County surveyor Tate found what he thought were original GLO corners, but instead were most likely manufactured corners to resemble GLO corners by a land locator helping settlers find their land. It went to the Supreme Court twice. There were a total of seven surveyors involved between 1882 and 1911 trying to figure it out. I'm in the process of writing a book about this case.
Can someone help me get a better grasp on the variations and how to describe them so the average person can comprehend? Thanks!
> Can someone help me get a better grasp on the variations and how to describe them so the average person can comprehend? Thanks!
I think making two diagrams of compasses for lines run on a vernier compass reading of "North" but at the East variation and the West variations would do it. Keep the compass needles parallel in both diagrams, give them declination arcs of exaggerated size, and show how different the line of sight through the vanes is.
Begin by explaining that the north magnetic pole is not the same as the north geographic pole and moves over the years, with a diagram of the usual situation, with the needle pointing N10E to account for the deviation (called variation in old notes) and sighting north.
Then explain that how different directions were easiest to run by setting the angle on the declination "variation" scale and letting the needle point to the "north" mark.
It's been a while
But I think whenever you see the degree symbol, you are supposed to take a drink.
You can think of it as just another way of reporting a bearing.
If I run south from a given corner with one variation, that describes exactly what was done with the compass. If he runs another line SOUTH from the same or a different corner in the same area with a different variation it is then at a different bearing from the first.
This can be done by the random and true process Kent mentioned (often used in the early PLSS surveys), or it could be he could see the destination corner and simply turned off the variation to get his needle N-S.
I have seen this quite a bit in earlier colonial and PLSS surveys.
You can use the historical declination models to try to get an idea of where the lines were actually run.
> Begin by explaining that the north magnetic pole is not the same as the north geographic pole and moves over the years, with a diagram of the usual situation, with the needle pointing N10E to account for the deviation (called variation in old notes) and sighting north.
>
> Then explain that how different directions were easiest to run by setting the angle on the declination "variation" scale and letting the needle point to the "north" mark.
Yes, I'd make the first compass diagram a compass with a declination arc set for 0° variation. Show the direction of true North and draw the diagram so that it is clear that the compass is pointing at magnetic North.
Then show the case with the declination arc set for the actual declination. Draw the diagram so it is clear that the compass is pointing at true North.
Then add the diagrams for the declinations mentioned, 10°30'E and 12°30'W.
Naturally, it all would have to be prefaced with some discussion of the secular change in declination and that declination differs from place to place.