RT_GPS_Vel_ECEF_1 X,Y,Z accuracy and X velocity
RT_GPS_Vel_ECEF_1: 140, 19 (0x8C1320 + unit id) (0x313)
Byte 0: Validity
Byte 1: Accuracy X (m/s)
Byte 2: Accuracy Y (m/s)
Byte 3: Accuracy Z (m/s)
Bytes 4-6: ECEF Velocity X (m/s)
Byte 7: Unused
ECEF velocities are velocities in the Earth-Centered Co-ordinate Frame.
Accuracy resolution is m/s * 0.1
Speed resolution is m/s * 1e-4
These measurements are from GPS data only.