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[aviadoz]

Hello,

I saw in rtabmap_ros.launch that there is an option to add imu data also (only in visual odometry I think).
I don't find any information about that. Can you give information about it please?

[matlabbe]

Hi,

It is quite an experimental feature, this is why there is no official documentation/tutorial on this topic.

IMU can be used for odometry and rtabmap nodes:
 - odometry: For visual-only odometry (VO) approaches (see Odom/Strategy parameter), the imu will be used to initialize the first frame accordingly to gravity (set wait_imu_to_init parameter to make sure IMU is received before processing the first camera frame). For visual-inertial odometry (VIO) approaches (see Odom/Strategy parameter), the imu will be used in estimation.
 - rtabmap: IMU can be used to add gravity constraints to graph, so that on optimization, the map will be aligned with gravity. Parameter Optimizer/GravitySigma should be non-zero to enable this feature. If input odometry is VIO (already aligned with gravity), we can set also Mem/UseOdomGravity to add those constraints to graph (subscription to IMU is then not required).

See https://github.com/introlab/rtabmap_ros/blob/master/launch/tests/euroc_datasets.launch for examples of usage with IMU.

cheers,
Mathieu