extrinsic rotation question

Question

extrinsic rotation question

Opened this issue 3 years ago · 6 comments

I have a Horizon mounted to a motor on a tripod running a 360 degree sweep in 3 minutes. The lidar unit is rotated 90 to the right along the X axis as you are looking at the lidar from the front to the back. Where would be the best place to change the angle of rotation? Should it be done in the driver or in livox mapping?
Since this is used as a TLS style scanner would it be best to use spherical or Cartesian coordinates in livox mapping. I tried using the livox_scanner repository but livox mapping is doing a better job, kinda. There is a 1 meter difference in the Z (Y) axis by the time the unit rotates a full 360. Any suggestions on settings that may improve the alignment?
thanks for putting out the different repository's for us to play with.

Answer 1 · 2021-06-07T13:05:26.000Z

Hi Rotoslider,

IMU may produce some error while rotating. Maybe try rotate a bit slower.

Answer 2 · 2021-06-07T14:06:10.000Z

Hi Rotoslider,

IMU may produce some error while rotating. Maybe try rotate a bit slower.
I rotated it a 0.5 deg per second. Thats 12 minutes to go 360 degrees around. Going slower did not help.

Answer 3 · 2021-06-28T07:07:29.000Z

Hi!
I think my problem is related. I'm testing mapping with MID-70 in small room (4mx5m or so). It seems that at some point rotation causes a drift or shift in room map.
It looks like this:

I'm not sure yet is it hardware or software problem. It looks like range measurements are wrong all of the sudden or are interpreted in wrong manner. Could it be that the lidar is broken?

Answer 4 · 2021-07-13T12:52:39.000Z

Hi Rotoslider

I think this is because the detected sense does not provide enough feature for mapping
Maybe try mapping in the outdoor environment.

Answer 5 · 2021-07-13T12:54:37.000Z

Hi ik-forknav,

I think maybe the Lidar is too close to the wall the detected sense does not provide enough feature for mapping
Maybe try mapping in a larger environment or outdoor.

Answer 6 · 2021-07-13T15:45:36.000Z

I have ran it outdoors in a forest with the same problem. It gets confused and fails to align correctly. The mount works great. I have done over 200 6 minute scans correctly with a velodyne but it always fails with the livox. I have tried 2 degree per second 1 degree per second and 0.5 degree per second rotation speeds. It seems the software can not align proper indoors or outdoors.