Re: Sextant accuracy with short distance to horizon
Subject: Re: Sextant accuracy with short distance to horizon
From: Yves Arrouye (yves@XXX.XXX)
Date: Fri Jun 29 2001 - 01:27:21 EDT
> I very much like your explanation why one should add the wave
> hight to the
> height of eye when observing from a wave top. Only for one 'but':
> your line of sight is tangent to the horizon, so for all
> practical purposes
> (wavelength assumed small w.r.t. curvature of earth) the
> horizon is formed by
> wave crests. There's no way of seeing a trough at the horizon
> because there is
> a crest relatively close in front of it. So both observer and
> horizon are
> raised by approximately the same distance (say, the
> significant wave height),
> and the dip should be calculated for the elevation of the
> observer above this
> raised horizontal level.
BTW this is what Bruce Bauer says in his Sextant Handbook. He also says that
on the bridge of a large ship, you want to correct for that, as only your
horizon seems raised by the waves.
YA
