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--- Alexandre Eremenko wrote:

> >  > in the same way our vision is.>

I have some experience with naval gunfire during the
Vietnam war.  When firing from a ship at sea at a
fixed target ashore, you need to know the location of
the target and your own location with precision.
Target location usually came from spotters on the
ground or in the air.  Within sight of land, nothing
beats an optical fix (from bearings of landmarks taken
with a gyrocompass and a pelorus).  A radar fix can be
quite good if the topography is suitable (for example,
rocky headlands).  Don't forget that radar gives you a
bearing as well as a range.

Once you know your location and the location of the
target, you can compute range and bearing to the
target.  Then, in order to hit the target, you need to
compute azimuth and elevation.  That is called the
fire control problem and involves the calculus
(integration if I recall correctly).  That was done
using mechanical analog computers (lots of gears).
The forward motion of the ship also needs to be
factored in, as does the wind, and also the roll of
the ship.  Mechanical gyroscopes were used to
compensate for the latter, so that the gun could be
fired at exactly the right instant.

The spotters then provided any necessary corrections.
This is called "walking it in".  I once heard a story
about an incident in the Korean War, in which U.S.
Army troops 10 miles inland called for gunfire support
from a U.S. Navy battleship offshore to destroy a
bridge.  The Army spotters called in the coordinates
and the first round was 100 meters long.  The second
round was 100 meters short.  The Army spotters, who
were used to working with Army artillery, started to
give the battleship instructions to "walk it in".  The
battleship responded, "No, we are ready to fire for
effect."  The next round destroyed the bridge.  (A
battleship fired a 2,000 pound explosive projectile.)

Best regards,

Chuck Taylor
 48d 55' N
122d 11' W


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