SCALED_IMU2 and RAW_IMU acceleration readings on BlueRoV2 R4

[EliotBR (Eliot)]

@Amhussey

I am wondering if there is documentation about using the RAW_IMU messages and converting them to m/s^2 measurements. Speciffically do i need apply an offset to the raw readings and conversion to proper units?

I haven’t looked at this in a while, and we don’t currently have decent documentation describing these values. Hopefully this comment (from a while ago) is helpful:

@EliotBR

The SCALED_IMU* messages provide their acceleration values in mG, which stands for milli-gravity (1000 x 9.80665 m/s2) - when the vehicle is stationary the zacc should be approximately -1000, due to the downwards force of gravity on Earth.

The MAVLink specification does not include units for the RAW_IMU messages, so they could technically be specific to the implementation or the sensor in use.

From the ArduPilot source code it seems like ArduPilot firmwares present the IMU data with consistent scaling …