# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: The development of bubble sextants
From: Gary LaPook
Date: 2009 Aug 15, 12:59 +0200

```Having fired many artillery projectiles over many miles of the earth's
surface I am familiar with coriolis. I can assure that once the
projectile leaves the tube that it flies in a straight line though space
but for an observer on earth, say an enemy platoon, it appears to curve
to the right. This is because the earth is turning under the path of the
projectile so we had to use tables to allow for this "Coriolis" and
ended up pointing the guns to the left of the target so the target would
rotate to the place that the projectile was aimed and they both arrived
at the same point at the same time.

Coriolis is a fictitious force use to explain the perceived curve of the
flight path as observed by an observer on earth of other rotating frame
of reference. See:

http://en.wikipedia.org/wiki/Fictitious_force

gl

douglas.denny@btopenworld.com wrote:
> Dear Gary,
>
> Coriolis is a very real acceleration. It is not fictional at all.
>
> The sextant (and person ) is being carried through space in a curved motion
by the Earth itself, and the acceleration due to curved motion is real
enough, just the same as if you are in the big Millenium Ferris Wheel in
London, or in a fairground 'Skyboat' device whizzing around in circular
motion.
> Coriolis just happens to be a small quantity - though relevant in
calculation if you are in a jet moving at around 400 knots.
>
> I have a theodolite made by British Aerospace with a North seeking gyro
built in which 'feels' the acceleration right enough to provide North to
within a few second of arc.
>
> Coriolis can be allowed for because the motion of the Earth is 'constant' so
the parameters can be calculated for the direction of travel and Latitude,
the main components affecting the apparent local gravitational field due to
Coriolis.
>
> Douglas Denny.
> Chichester. England.
>
>
> >
>
>

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