RT_INS_Vel_ECEF_2: INS Y and Z Velocity
RT_INS_Vel_ECEF_2: 142, 19 (0x8E1320 + unit id) (0x393)
Byte 0: Validity
Bytes 1-3: INS ECEF velocity Y (m/s)
Bytes 4-6: INS ECEF velocity Z (m/s)
ECEF velocities are velocities in the Earth-Centered co-ordinate frame.
Speed resolution is m/s * 1e-4
Accuracy resolution is m/s * 1e-2
Accuracy is an approximation to the 1 sigma standard deviation of the velocity value.