[bontai Joe]

If you have a clear line of sight to the missing point while standing at point "A" or at point "C" you can set up a step ladder or some other portable platform and lay a cheap plastic protractor on it. Sight down the angle mentioned in your survey towards the missing point and measure out the distance. You can lay a pencil on the protractor and look down it, or if you want to be really fussy, screw the protractor to a scrap piece of wood and then pound in a couple of finish nails into the wood to use as aiming points. Depending on the distances involved, you can get pretty darn close doing this. I would think you could be within 2 feet on a 400 foot property line using a little care.

 

[bontai Joe]

Many, many years ago (before the war as grandma used to say) I worked part time after school and summers for a land surveyor. We often had to play hide and seek for old property corners. I got to the point that I could get pretty close on distances, just pacing it out. But that was over 45 years ago.

 

[bontai Joe]

Just Jeff - Now that you have 10 ways from Sunday to find that corner, you need to put on your industrial strength DEET and mosquito netting and find that corner! We're all waiting with bated breath for the results

Actually this has been a fun and challenging post, identifying info and sources and methods to do this. I am retired over 13 years from doing this stuff, and I was pretty old school even then.
One interesting thing is how much folks rely on technology that is unreliable - like believing that a GPS will get you to a pinpoint on the ground. It's great stuff, but everything has its limitations.

This thread brought back many good memories for me. I worked summers as a part timer with a land surveyor back in the early 1970's when I was a teenager. That would be the very early days of LASERS and radio distancing. I have fond memories of "pulling chain" along thousand plus foot long property lines, 100' at a time. And I have many not so fond memories of being eating by various insects that both fly and crawl. I also remember the boss taking our field notes and doing the calculations to make sure our survey "closed". The distances measured and the internal angles are computed out to prove we ended at the same point we started from (a good thing!). A four sided property was easy, the angles add up to 360 degrees and the geometry wasn't too tough to calculate. The properties with a dozen or more sides and a couple of radii tossed in for fun got complex pretty quick.

 

[bontai Joe]

Degrees still add up to 360 regardless the number of bends. Always a good thing to know.

The internal angles of a triangle add up to 180. A pentagon shape has internal angles that add up to 540 degrees. The more sides, the higher the number goes. And adding in a radius or two that borders a bend in the road, or worse, a wobbly line that follows a river goes well above my ability to compute.