Orientation of sensors on the ultimate IMU

Hi Guys

I’ve been working pretty hard trying to get a 13-state kinematic EKF up and running in Matlab. I’m using raw data inertial and GPS data from the Ultimate IMU to test the filter. The stock firmware provides a method of saving to two files – NMEAXXX.csv and SensorXXX.csv. From what I can tell there is no documentation that states clearly the coordinate frame used for X, Y and Z, as well as the units of the incoming data.

Here is what I believe the gyro/mag/accelerometer sensor orientation to be, based on the datasheets:

http://tinypic.com/r/35381ns/7

In Ryan Owen’s Ultimate IMU code (https://github.com/ryowens84/Ultimate-IMU) he provides a simple filter to fuse the gyro/mag/accelerometer data. From what I can tell, the code makes the assumption that the axes of the three sensors are aligned. However, the datasheet suggests that the HMC5843 has a different orientation to the other two sensors. Surely, this would affect the bearing / yaw reading? I’ve been experiencing issues with my yaw readings.

Additionally, it looks like the accelerometer, gyroscope and magnetometer readings are in gravitational units (G), degrees per second and Gauss respectively. Can somebody please confirm this!

Thanks

Andrew