I could use some assistance in explaining magnetic variations on GLO plats. The two examples below are from two different deputies working in the same area of central Nebraska. I have shown images of only the four southeast sections of each township for simplicity sake.
Assuming the surveying was done correctly. The deputy was supposed to first retrace the east line of Section 36 on the township line to compare the meridian. Then begin the subdivision of the township by running north from the SW Corner of Section 36 parallel with the east line of Section 36.
Notice in the first example, all of the magnetic variations on the north-south lines are v. 13°15' East which agree with the east line of Section 36.
Notice in the second example the north-south lines vary 5-minutes from the east line of the township, and then 10-minutes on the second mile west. The variation on the west lines of Sections 35 and 26 are also 10-minutes different. The west line of Section 26 would have been run within hours of the west line of Section 35. What is taking place here? Magnetic disturbance would not be an issue here as this area is only sand.
Then begin the subdivision of the township by running north from the SW Corner of Section 36 parallel with the east line of Section 36.
The variations are the same but the lines won't be parallel. This will produce converging lines.
I can't recall seeing 5 minute shifts that you show in the second example.
Now that I look at some I see a number of shifting variations on original plats. Most of them hold one number through the entire plat, but some are changing and in different amounts.
Frankly, as a BLM resurveyor, I did not pay any attention to these notations on the plat!
Keith
Improper use of the solar compass comes to mind. Something metal nearby that affected either the trough compass on the solar or another regular compass. I could go on and on with ideas, but frankly with what we see back here in my neck of the woods I'd agree with Keith about not paying much attention.
Were the lines run with a solar instrument, so he is maintaining his best shot at constant bearings, and just noting the variation because it is required of him?
Since most of my career has been spent trying to retrace Benson Syndicate and related era work, I tend to believe 95% of the whole plat is faked, except where there is prime bottomland and along easily traversable ridgelines.
>
Are there in fact no topographic features within the area shown on the above plat that would ordinarily have been noted by the surveyor? If there are, is this evidence that the plat may be partly fraudulent? I trust you've examined the record of magnetic variations observed at about the same time in the surrounding townwhips and have found them to be a bit more uniform than as shown in the above.
Another question that comes to mind is whether that township was subdivided by a non-standard method and the variations on the lines are a clue. For example, if the North lines of Sections 36 and 35 were run first and the variations of the West lines of 36 and 35 were calculated from some falling further West on the same course, that could explain the odd range of what would in effect have been calculated variations.
If you examine just the subdivision lines within the township that are noted with a variation of 13°20', does that pattern make any particular sense?
I have never given these notations much thought or even consideration, however I have been asked to explain the notations on GLO plats for an upcoming mini course on what the GLO surveyors did. Of course the surveys were most likely partially fraudulent, however I doubt the deputy would not have knowingly placed bad information on his plat to convict himself. A lot of surveyors maintain that this information is crucial for retracement.
> Of course the surveys were most likely partially fraudulent, however I doubt the deputy would not have knowingly placed bad information on his plat to convict himself.
Actually, if my hypothesis is right, in the second example you gave, the surveyor would have been trying to cover up the fact that he hadn't actually run the West lines of Sections 36 and 35. That is, the variations that he noted on the plat would have been his best estimate of the variation that would be needed to run true line. So, some surveyor starts at the SW corner of Section 36, runs North at that variation and actually falls reasonably near the NW corner of the Section. That would tend to lead a person to think that the line actually was run as shown on the plat.
This is getting ahead of the story, of course, but on some townships that were subdivided by shortcut methods, the odd variations on some lines and not on others may be very good clues to what was actually done.
Seem to recall that the mag variations were partly required so to help identify where areas of mineral deposits were located. I won't swear on it as I can't recall where I read or heard that.
Like Keith though I never saw anyone use that info in my Cadastral days other than when trying to retrace a rancho boundary.
sorry not much more help.
It looks like he is correcting for convergence of the meridian by changing the setting of the variation on his compass. They were running the lines with the compass. At some point the procedure was changed and the bearing was changed for this correction (true bearing shown for the line). At the east side of the township you run north then the bearing of each tier would increase something NW say a minute more for each line (dependent upon latitude of work) to keep the sections more square to correct for the convergence then all the non squareness would be left on the west side. I'm not sure when this all started seems around about 1890 from my experience (don't see it on plats before but do after). I don't know what the dates of these plats are but maybe it was a transition period when they were trying different things, maybe he had special instructions. Maybe it's just goofy. I can see if you were running the line with a compass you might use this short cut method to correct for convergence.
I thought the plats were done by the GLO in their office. The deputy just returned field notes.
clearcut,
You are right in trying to retrace some of Benson's work and I would suppose that you and others in California, especially in BLM, know where to find him and where not to even look.
The last township that I resurveyed in Montana was originally surveyed by a notorious deputy that it could be predicted with certainty, where he was and was not. Out on the flats, there were monuments, but up in the breaks, nothing.
Regarding the notations on the plat on the variance, I would have to do research , can assume that it was required to give the information, even tho I would suspect it was guessed at in numerous situations.
Thus, was not paid attention to.
Keith
I think the BLM guys have that all figured out, for the last hundred years or so!
> I think the BLM guys have that all figured out, for the last hundred years or so!
Possibly no fraudulent plats have been recorded at the BLM since 1913, but the plats Jerry Penry posted are probably from the 1860's. Obviously, the USGLO either did not have any way of reliably detecting fraudulent surveys or actively abetted it during some period. Otherwise, there wouldn't have been so many plats of such work accepted, eh?
Kent,
That is a good point and I have often wondered too, how so many fraudulent surveys happened and were approved.
For instance, when a survey comes in to the office for examination and approval and it is shown that the Continental Divide runs through the township, and the township survey was accomplished in 6 days; would that not arouse some suspicion?
Keith
The dates on the plats are 1872.
Say for instance the deputy set the NW Corner of Section 36 per instruction, and then measured to the existing corner at the NE Corner of Section 36. The distance is what it is, but perhaps it was found to quite a bit greater or less than 80 chains. The deputy then readjusts to go north from the NW Corner of Section 36 along the west line of Section 25 in order that the north line of Section 25 is closer to 80 chains? There would therefore be a P.I. at the NW Corner of Section 36?
I took me a bit to refind the plats. Actually they were done by the same surveyor, Chaunsey Wiltse, who was known as a good surveyor.
Oh, Lord, Kumbaya.
Kent
That is a good point...
Words that I could never have imagined passing Keith's lips.
Hell has frozen over and there is a possibility of peace in the Middle East.
I respect both of these Beerleg characters a lot, but, man, they used to snarl at each other:-)
Don
I believe this answers my question pretty thoroughly. Taken from "A Treatise on the Method of Government Surveying" by Shobal V. Clevenger, U.S. Deputy Surveyor. 1883.
I have marked on the third page (page 29) where it says to adjust the variation on the next course north if the east-west line across the north side of a section measures different than 80 chains. Obviously there must have been a certain tolerance number that the surveyor used in determining if he was going to readjust.
