Larry W4CSC wrote:

It's quite a sight to see her turn perfectly on her central vertical
axis, without the current pulling her away in the process. The old
PDP-8 did a good job, I suppose.

Spent quite a bit of time on a dynamically positioned drillship in the
Med and West Africa and off Labrador. It used a Honeywell DP system to
maintain position over a wellhead more than 5000 feet below.

The system used acoustic transponders and a "riser angle" input to
control the ships screws and 4 retractable thrusters and could maintain
position within about a 50 feet circle in Winter open ocean conditions
between Labrador and Greenland. It was an amazing system for its time.

The DP operator could bypass the computers and use a joystick and a
polar display to move the ship manually. This was used whenever we
reentered the drill hole during initial drilling ops.

I was a submersible pilot we and would sit on the bottom (down to 5800
feet) and visually direct the DP operator to move Xx feet XXX degrees
and then DROP when the drill bit was located above the guidebase.

Rick