Ray ground filter : Spotty ground removal

[MaxandreOgeret]

Bug report

Required information:

• Operating system and version:
• Autoware installation type: Source
• Autoware version or commit hash : 411330c
• ROS distribution and version: Melodic
• ROS installation type: apt
• Package or library, if applicable: ray_ground_filter

Description of the bug

I have noticed that the no ground pointcloud is very sparse and that a lot of points on the obstacles are classified as ground even though they shouldn't.

Steps to reproduce the bug

• Use ray_ground_filter on a high density pointcloud

Expected behavior

No 'spots' of ground points between vertical points on obvious obstacles.

Actual behavior

The obstacles are scattered with ground points and vertical points.

Screenshots

Source of pointcloud : Ouster OS1 128 beams.

• Man at 40m : (Orange = vertical points, grey : raw cloud)
  

• Man at 3m : (green = ground, pink = vertical)
  

I have tried to reduce the radial_divider_angle to 0.006 as sensor is running at 1024 samples per rotation and : (2*PI / 0.006 ≈ 1024).

• Man at 40m : (green = ground, pink = vertical)
  

• Man at 3m : (green = ground, pink = vertical)
  

Additional information

I have tried before and after PR #12 and the result is the same.

Here is the config we use :

lidar_center:
  ray_ground_filter:
    base_frame: base_link
    ground_point_topic: /lidar_center/points_ground_test
    input_point_topic: /lidar_center/points_raw
    no_ground_point_topic: /lidar_center/points_no_ground_test
    clipping_height: 1.8
    # min_point_distance in platform_params
    radial_divider_angle: 0.05
    concentric_divider_distance: 0
    local_max_slope: 8
    general_max_slope: 8
    min_height_threshold: 0.4
    reclass_distance_threshold: 0.5
    sensor_height: 2.23
    min_point_distance: 2.0

I can provide a bag if needed.

Thanks !