motion decorr readme

sonic motion files contain 10 columns: [jd_10Hz,uvwplat,xyzplat,euler]
where uvwplat are platform velocities (m/s), xyzplat are platform
displacements (m) and euler are roll,pitch,yaw angles.  Note that
coordinates are rotated into the earth frame ( u and x are N-S, etc.).

roll_pitch_yaw files are euler angles in the ship coordinate frame, 
saved in .mat format.