Sometimes point cloud tilts

[Jaetriel]

Hello, I noticed after trying out some scans that sometimes, maybe more often visible if you move up/down floors or stairs, the whole point cloud from FAST-LIO tilts a bit, even though I make sure to start the device perpendicular to the ground to get the right orientation. I am thinking this may be caused by wrong extrinsics between lidar and imu? Or possibly a mismatch in the timestamp sync or maybe just a product of using a 6 axis IMU and not 9?Is it possible to adapt FAST_LIO to use 9-axis IMU? I will attach some pictures of a scan to try and make it more clear