RT_Directional_Speed Calculated speed (signed)
RT_Directional_Speed: 128, 16 (0x801120 + unit id) (0x011)
Byte 0: Validity
Byte 1: Accuracy
Bytes 2-5: Combined speed (m/s)
Bytes 6-7: Unused
Combined speed resolution is m/s * 1e-5.
Accuracy resolution is m/s * 1e-5.
This is the 3D speed output from a combination of GPS and inertial signals. This value is positive if the vehicle is travelling forwards, and negative if travelling in reverse (sign is actually set by the orientation of the sensor; the preceding is true if the sensor is mounted with the correct orientation with respect to the vehicle).
Accuracy is an approximation to the 1 sigma standard deviation of speed.
Note: This message is only available from the SPEEDBOX-INS.