Hi guys

I have a bit of a transformation challenge to deal with here.

I have modelled the sensor outputs of a 3 axis ring laser gyro system which detects the earth's rotation. As you can see in the first image, a simple atan2 of the Prate and the R rate is sufficient to determine true heading. However if the local horizon pitch or bank angle is changed, I can no longer use a simple atan2.

In this second image, you can see pitch is set to -1.5 deg. Now the R rate has decreased and I have a signal on the Y rate gyro. This produces an error in the atan2 output even though actual heading has not changed. Any suggestions on how to correct for this? I haven't been successful in my attempts to invert the pitch and roll rotations.

Thanks

JB

(facepalm)

I have done this rotation on numerous occasions before. Somehow I got my sines and cosines mixed up. Resolved.