I believe there is no correction for elevation. The angle that is being measured is the
height above the horizon, which is presumed to be a plane tangent to the surface of the
Earth. There is a correction for the elevation of the observer above water level. As
long as there is a clear horizon, the altitude is not relevant.

Actually, the angle of interest is the difference from directly overhead. Since we know
the spot on Earth directly below the star at a particular point in time, the difference
from being directly overhead implies a "circle of position" of the appropriate radius on
Earth. For example, if we assume the North Star is directly over the North Pole, then if
it is observed 20 degrees away from directly overhead, the observer must be on a circle 20
degrees away from the Pole, or 70 degrees North latitude.

Check out any basic celestial navigation book - this will be explained much better than I
can.

Off course, I don't know how much celestial was ever done on the Great Lakes - you're not
very often out of sight of land.

--
-jeff
"Constant Vigilance!" - Frances W. Wright



Matt Ashbrook wrote:
Just wondering...on the oceans, navigators use a sextant for out of
sight of land navigation. How is it done on the Great Lakes where
they're not operating at sea level? Of course, I'm talking about the
absenceof electronics. Anyone know of any literature on this?

Thanks,
Matt A.