Double walls in Realsense dual mode

[quizzy5889]

Hi Mathieu,
I am quite new to rtabmap and I am doing the first tests to try to reconstruct an indoor environment in RealSense dual mode (T265 + Lidar L515).  I tried to search a bit in the documentation, but I'm not sure if anyone else happened to be in the same condition.

Basically, L515 and T265 were accurately placed with a known transformation between them. The transformation was entered as an input parameter.

The problem is that during the reconstruction some walls appear double and I don't understand where the problem could come from:

* The rolling shutter of the RGB camera causing an inaccurate loop closure? However, it does not seem to me that there were any loop closures in this case.

* Inaccurate mounting?

* ICP?

Could you kindly direct me on how to try and debug the problem?

I attach all attachables

Thank you very much,
Andrea




config_L515_T265.ini

[quizzy5889]

I forgot the db. Here it is.

https://drive.google.com/file/d/1LcVPvXhX-7X71ESBd2I0eIAdcu_pAKX3/view?usp=sharing

[matlabbe]

Hi,

The double walls can be caused either by odometry drift or not so accurate transformation between the cameras, or both.

There is also no loop closures detected. For visual loop closure detection, you should traverse the same areas in same camera orientation. In your trajectory, there is an overlap in the trajectory, but in not the same direction, so no visual loop closures can be detected.

It is possible to calibrate the extrinsics between the camera using the Calibrate Extrinsics button in latest rtabmap version:


To make it work, you will need to calibrate the T265 (with realsense sdk 2.42, newest sdks have this issue), then do the extrinsics calibration.

cheers,
Mathieu

[quizzy5889]

Hi Mathieu,
First of all thanks for your answer.

Just to be sure: Does the issue related to the librealsense version affect only the calibration procedure or the entire process?

In other words: if the extrinsics between the T265 and the L515 are accurately known, may I use the latest librealsense version?

Thank you

Andrea

[matlabbe]

Hi Andrea,

Yes, you can use the latest realsense sdk version if you can manage to find the accurate extrinsics between the cameras (without using rtabmap's extrinsic calibration tool to do so).

cheers,
Mathieu