Sextant Positions versus Map Datums?
Subject: Sextant Positions versus Map Datums?
From: Jared Sherman (jared.sherman@XXX.XXX)
Date: Tue Jan 15 2002 - 13:04:57 EST
Okay, a sextant position is based on the almanac which is based on...ergh...How exactly does that match up to a map datum? Should a sextant position line up with a WGS84 chart position? An NAD27? A what-ever-is-most recent datum? Or can it be expected to be off by...What distance actually?
If NAD27 and WGS84 disagree by a mile, then wouldn't the "most accurate" sextant position still either be off by a mile, or have been off by a mile? Or maybe still be off wherever the map datum doesn't match a "spherical earth" model?
How exactly does one accomodate the "no datum here" from a sextant position? Aside from the fact that the difference may be meaningless out at sea, where the maps all agree that "you are here" in the big empty spaces and a mile or two doesn't always matter.
