Definition of orientation of insfilterErrorState function with ENU reference frame?

Dear community members,

what is the definition of yaw angle in insfilterErrorState of ENU frame? It's about the angle between enu local x axis and enu global x axis or its about the angle between enu local x axis and north?

filt = insfilterErrorState("ReferenceFrame", "ENU");
filt.IMUSampleRate = 100;
filt.ReferenceLocation = [lat0 lon0 alt0];
qeul = quaternion(deg2rad([yaw0 pitch0 roll0]), 'euler', 'ZYX', 'frame');
filt.State = [compact(qeul),[0, 0,0], [0, 0,0], [0,0,0], [0,0,0], 1]';

Best regards

Answer 1

[Brian Fanous]

The filter estimates orientation as a quaternion. The orientation is the identity quaternion (i.e. quaternion(1,0,0,0) ) when the body's x axis is aligned with East, the y-axis is aligned with north, and the z-axis is aligned with up.

In this convention, if you convert that orientation to Euler angles with the ZYX convention, then the first Euler angle is the angle between East and the x-axis of the body.