A C++ and python ROS package that fuses the accelerometer and gyroscope of an IMU to estimate attitude.

-This node subscribes to sensor_msgs/IMU messages on the topic '/imu/data', containing accelerometer and gyroscope data.

-This node publishes a quaternion to 'AHRS_EKF_quat'.

-To visualize, run rviz, create an Axes and change the reference frame to 'ENU'. Create another Axes and change the reference frame to 'IMU'.

Wait for 5 seconds for the initialization procedure. Update the following noise terms inside code for your IMU:

	sigma_xg # Gyro (rate) random walk  
	sigma_nug # Gyro white noise  
	sigma_xa # Accel (rate) random walk   
	sigma_nua # Accel white noise  

Tested with Xsens MTI-20 and Sensonor STIM300. Primary reference is 'Aided Navigation: GPS with High Rate Sensors' by Jay A. Farrell, chapter 10.