Rotation Sequence

Roll, pitch and yaw corrections are applied with the rotation matrix. With such a matrix, coordinates are transformed between different reference frames. The vectors in the 3D-window present the axes of the local level frame (LLF). Recall the convention as used in synSwath:



Roll Pitch Yaw

When the platform turns arround one of the axes you’ll notice another set of axes. These axes move together with the platform and are thefore refered to as the body fixed frame (BFF).

Transforming from one reference to another follows with a the rotation matrix. To transform for example from the BBF to the LLF:


The Rotation matrix (R) is in fact a product of all the rotations, thus it is the result of a series of three rotations matrices (rotation around x, y,z). This is where the rotation widget comes in place. It allows you to examine different rotation sequences. The most common rotation sequence is the Tate-Bryant convention. It first applies a rotation arround the z-axis (yaw), then around the y-axis (pitch) and finally around the x-axis (roll). Note that each rotation is subject of the previously applied rotation. So the second rotation around the y-axis is subject to the rotation around z, and the final rotation around x was subject to rotations around y and z previously.

Thus it will first correct for the yaw, next for the pitch, and finally for roll angles.

Becoming bit confused? So was I ......., try this:
In the Tate-Bryant sequence first give a +90° heading. Then give the platform a pitch. You’ll notice it now indeed pitches around BFF x-axis and not the LLF x-axis. Now choose another sequence, for example P-Y-R. The platform is now first corrected for the pitch so the platform is turned around it’s BFF y-axis (which initially was the same as the LLF y-axis). Then the yaw is applied, so it turns around BBF z-axis. So resuming:
With Tate-Bryant it first corrected for yaw (ryaw), then pitch (rpitch), and then roll (rroll).



With P-Y-R it is corrected first for pitch, then yaw and finally roll.


When you set either the heading or pitch back to zero (hit ’z’ while mouse on slider bar) the platform points in same direction for both cases. Hit '7', '8' or '9' to change the view to respectively top, SB-side and front side.
The Hippy sequence has it’s origin from the Hippy motion sensors. It uses the same convention as Tate-Bryant (y-p-r) but uses the sine and cosine of the pitch as roll and yaw values. Don’t know why???


last modified: 09-06-06, Pim.