(odd) courses in old deeds

http://en.wikipedia.org/wiki/Points_of_the_compass#32_cardinal_points

Thanks....that's pretty interesting. I hadn't seen it before

I am curious about calculating the uncertainties when trying to place older deeds on the ground that use the north-northwest type bearings and distances rounded to the nearest foot. This seems to be a good problem for your least squares program?

I don't run across these types of bearings very often.

In the early days of the colonies there were quite a few surveys reported in this manner. Probably because a mariner's compass was being used and the circle was not divided into degrees. Also, the survey was probably being run by a sailor rather than a surveyor. If I can find it I'll post a page from George Washington's student copy book where this was part of his studies.

Here is the page from George's book when he was studying surveying:

> I am curious about calculating the uncertainties when trying to place older deeds on the ground that use the north-northwest type bearings and distances rounded to the nearest foot. This seems to be a good problem for your least squares program?
>
> I don't run across these types of bearings very often.

I don't think I've ever seen the points of a mariner's compass used for directions in any deed or land description in Texas. As far as the uncertainties go, if each direction is assumed to have an actual value that is somewhere within an 11.25 degree band, 5.625 degrees from the nominal median value, then it would be reasonable to give the directions standard errors of about +/- 3.8 degrees since that tolerance would catch about 68% of the 11.25 degree band.

North by Northwest

I have seen it once (1900 era) and the deed did not appear to fit anything on the ground, nor were any monuments apparent. Our survey was never performed, but there was some discussion about the uncertainties resulting from the directions given.

It would have been an interesting survey for sure.

:good:

Did you know there is a house with airstrip on top of Mount Rushmore?

Yes, and even later deeds might contain compass points if near areas where mariners would be common. I give one to students just to expose them to it. The deed is from Missouri mid 1800's.

Should have been Northwest by North.

> I have seen it once (1900 era) and the deed did not appear to fit anything on the ground, nor were any monuments apparent. Our survey was never performed, but there was some discussion about the uncertainties resulting from the directions given.

Come to think of it, I now recall having seen field notes from a traverse run in the 1830's to map the meanders of a river in which the directions N45°E, S45°E, S45°W, and N45°W were noted as NE, SE, SW, and NW, mostly for compactness.

Least squares would probably make a good approximation of the courses. However, in these cases one can only hope that there are calls in the deed to controlling monuments so that the uncertainty could potentially be restrained to just a few courses.

Very interesting. This suggests that use of the mariners' compass was common enough that a surveyor would know how to convert the bearings as a matter of course.

Here's another Washington example (1760). He didn't do the survey on which these bearings appear, but he made a hand copy of the drawing. It's hard to say how both degrees and marine bearings ended up on the same survey, but there they are. Distances seem to be in rods.