ex-meridian sights -
Subject: ex-meridian sights -
From: Russell Sher (rsher@XXX.XXX)
Date: Wed Feb 14 2001 - 01:06:34 EST
Barrie - Your suggestion is in fact something that I have seen in a
navigation examples book of mine. It is possible if the body is close to the
observer's zenith around LAN to plot the circle of position (COP) from the
altitude (since HO will be large and the COP radius small). Of course the
altitude may be a bit too close to 90 degrees for a desirable observation.
Then a LOP is taken just after (or could have been just before) this and the
COP intersected with the LOP - assuming that the distance run between the
two was insignificant. Perhaps someone has tried this.
barry wrote...
Most interesting. The Ex meridian method stems
from ancient times before the good Marc. Ste. Hilaire position line method.
However it appears
to be time honoured especially with DOT examiners. What has always
interested me is
why not simply use a sight taken 10 or so minutes
before or after noon ( up to 30 or so minutes
allowed by ex-merid tables) as a simple P/L. It
can be used with future or past P/L's to give a
position. (snip...)
