Asymmetric laser scan angle limits cause misalignment between scans and map grid cells during mapping

[KishanSawant]

Required Info:

• Operating System:
  • Ubuntu 24.04
• Installation type:
  • binaries
• ROS Version
  • ROS2 Jazzy
• Gazebo version
  • Gazebo Harmonic
• Version or commit hash:
  • feature/nav2
• Laser unit:
  • gpu_lidar (in Gazebo)

Steps to reproduce the issue

Update the laser angle limits in the urdf file:

test1: symmetric limits
max_angle="1.7"
min_angle="-1.7"

test2: asymmetric limits
max_angle="2.1"
min_angle="-1.7"

Run the mapping launch file:
ros2 launch slam_toolbox online_sync_launch.py

Config file: mapper_params_online_async.yaml
mapper_params_online_async.md

Expected behavior

For test1:

Actual behavior

For test2:

Additional information

For test2, the issue persists even after completely mapping the environment

[SteveMacenski]

That is not surprising to me - it is a non-feature that the FOVs of lidars are non-symmetric. You can make this virtually symmetric by using a Laser Filter to set the values of the filtered angles to 0.0, or INF so that they are not considered. That would create a data structure for the internal SLAM that is symmetric, whereas the ~0.4 missing would be replaced by non-values