A gyro compass is affected by 2 errors. Speed error and latitude error.

Question

I have no idea why this should be.

Can anyone offer an explanation.

Thank you,

Mike.

Since this is not my area of expertise, I searched Google under the key words "gyro compass error speed latitude" to get these possible sources:

http://ams.allenpress.com/amsonline/?request=get-document&doi=10.1175%2F1520-0426(1997)014%3C0211:CAGUAA%3E2.0.CO%3B2
http://www.tc.gc.ca/marinesafety%5CTP%5CTp3668%5C6standard.htm
http://www.navis.gr/navaids/gyro.htm
http://en.wikipedia.org/wiki/Aircraft_compass_turns
(Broken Link Removed)

I hope this helps. Thanks for asking.

What are the extra points on a compass?

Motion causes a gyro to precess, the faster the speed, the more precession. It takes some time to dampen the precession, so error is introduced.
Latitude is another pseudo source of error. Remember that Gyros point to a direction in SPACE, not on Earth. Assume the gyro is point to North, some point very near the direction of Polaris. Now near the North pole of Earth, the gyro will point to where? Not the N pole of Earth, but to the point in space near Polaris. So the "error" we observe on earth is trying to read the direction of the gyro, as it is projected on the surface of Earth. As latitude is increased, the error projecting the Earth tangential component is increased, in fact, the error varies as the tangent of Latitude. So at the equator, the projection accuracy is tangent of 0 degrees, or zero error. As one gets closer and closer to the N pole, the error becomes very large. The calculation of this error is complicated, and it is on top of other errors in the gyro.