Fernando Cabral <[EMAIL PROTECTED]> writes: > Just put a vertical stake on the. You can also use a plumb line with > a node somewhere at a suitable hight. Now, at chosen intervals, > like 9 o'clock, 10 o'clock... until noon, mark in the ground where > the stake shadow ends. For each mark, draw a circle having > the stake as the center. > > In the afternoon, mark where the shadow is at each corresponding > hour. That is, 1 pm, 2 pm and 3 pm corresponding, respectively > to 11 am, 10 am and 9 am. > > Now draw a line connecting each pair of hour. Now pick one of the > lines and bisect it and draw a perpendicular line. This line should coincide > with the noon line. Also, if everything is ok, this perpendicular should > bisect all the other lines. > > If the stake if correctly placed in the vertical you will end up with a very > precise North/South line from which you can find any azimuth you > may need. (By the way, the closer the solstice on the "other" hemisphere > the more price the measuring will be). > > I do think this method is easier and more precise than the compass and > the GPS (at least in "normal" usage).
I agree that a shadow method is likely to be easier and more precise than using either a compass or GPS, but I have some comments on your exposition. First, the clock time of the readings is not important. In the afternoon, you want the locations where the shadow of the nodus crosses each circle, regardless of what your watch says the time is. Second, the accuracy of the result can be compromised if the ground is not level from East to West. For high precision, you will first need to prepare a level surface for the shadows to fall on. Regards, Art Carlson
