|
|
Subject: Re: Sextant accuracy with short distance to horizon
From: Dan Allen (danallen@XXX.XXX)
Date: Thu Jun 21 2001 - 11:59:16 EDT
I've spent more time on land standing on 300' cliffs than on boats, hence
my remembering 20 miles.
I also remember from many years ago driving many times across the Salt Flats
of
Western Utah: there is a single stretch of road that is 40 miles long, dead
straight. I could see the lights of Wendover UT/NV from about 18 miles away
when
I drove it at night.
Dan
-----Original Message-----
From: Navigation Mailing List
[mailto:NAVIGATION-L@XXX.XXX
Emerson
Sent: Thursday, June 21, 2001 7:47 AM
To: NAVIGATION-L@XXX.XXX
Subject: Sextant accuracy with short distance to horizon
Dan Allen writes:
[...]
> This led me to think more about possible inaccuracies of using a horizon
> that is very close rather than naturally far away. That is, typically
you
> use a horizon that is at the limit of your vision, perhaps 20 miles away.
[...]
While you're in Bowditch, check out table 12, "Distance of the
Horizon". Assuming you're 6' tall and standing on a deck 4' off the
water, for a total height of eye of 10', the horizon is 3.7 miles
off. A twenty mile horizon requires a height of eye of something like
300'. And clear air. [grin]
Rick
S/v One With The Wind, Baba 35
|