Less than 1/2 a degree true on the equator. They start getting less accurate beyond the 70th parallel and the bearing will shift a
bit at speed above 30 knots vessel speed. Today's modern gyro compasses all have two gyros within the gyrosphere whose planes are
offset by typically 90 degrees to make accuracy better above the 70th. They don't like acceleration much and high ROT numbers, but
the high ROT (higher than 20 degrees per sec) is mostly the limit on the repeater, not the gyro. Of course digital bearing
displays have no ROT limit.

Historically, gyro compasses has been considered the most significant weapon innovation of WW1. With the advent of long range
naval guns and steel ships, the magnetic compass was almost useless. The big disadvantage is the high cost. Today, the same
accuracy can be achieved with satellite compasses with no latitude or speed limitations at a much lower cost of both acquisition
as well as life-cycle cost.
Steve

"Werner" wrote in message ...
On 12/05/10 14:14, scarlett99 wrote:

----- snip


I am on a survey boat need very accurate headings.



Question:

The concept of a gyrocompass on a ship was new to me. I read up a bit
and I think the difference to a whisky compass is that variation and
deviation have no influence.

What kind of reading accuracy can one expect when it gets "a bit choppy"?

5 Degrees with dampening, maybe?

Thanks
Werner Dahn