PCD to Grid Map Conversion and Saving as PGM and YAML Files

This program converts PCD (Point Cloud Data) files into grid map messages in a ROS2 environment and publishes them on a specified ROS2 topic. Additionally, the program supports saving the grid map directly as a PGM image file and a corresponding YAML metadata file.

Features

• Point Cloud Processing: Utilizes the PCL library to process the input PCD file, including pass-through and radius filters.
• Grid Map Generation: Converts the filtered point cloud data into a grid map format with customizable resolution and point count thresholds.
• File Saving: Supports saving the generated grid map as a PGM image file and a YAML file containing the map metadata.
• Real-time Publishing: The generated grid map is published in real-time via a ROS2 topic for other ROS2 nodes to subscribe to.

Dependencies

• ROS2 (recommended version: Humble)
• PCL library
• OpenCV

Installation

1. Clone the repository into your ROS2 workspace:

   git clone https://github.com/yuguangxie/pcd2pgm_ros2.git
   cd ~/your_ros2_workspace
   colcon build

2. Build the workspace:

   colcon build

Running the Program

Launch the program with the following command:

ros2 launch pcd2pgm pcd2pgm_launch.py

Configuration Parameters

You can configure the following parameters in pcd2pgm_launch.py:

• file_directory: Directory where the PCD file is located and where the output files will be saved.
• file_name: Name of the PCD file (without the extension).
• thre_z_min: Lower threshold for the Z-axis, used to filter out unwanted points like ground.
• thre_z_max: Upper threshold for the Z-axis, used to filter out points above a certain height.
• flag_pass_through: Whether to enable the pass-through filter, enabled by default.
• thre_radius: Radius threshold for the radius filter, controlling point cloud sparsity.
• map_resolution: Resolution of the generated grid map (size of each grid cell).
• thres_point_count: Point count threshold for the radius filter, determining point cloud density.
• map_topic_name: The ROS2 topic name where the grid map will be published.

Output

The program will generate the following files and save them to the specified directory:

• PGM File: The grid map image file (e.g., map.pgm).
• YAML File: The metadata file for the grid map (e.g., map.yaml), containing map resolution, origin, occupancy thresholds, etc.

Example

Suppose you have a point cloud file named test.pcd that you want to convert into a grid map and save. You can configure the parameters in pcd2pgm_launch.py as follows:

file_directory: "/home/user/pcd_files/"
file_name: "test"
thre_z_min: 0.1
thre_z_max: 1.5
flag_pass_through: True
thre_radius: 0.5
map_resolution: 0.05
thres_point_count: 2
map_topic_name: "/grid_map"

After launching, the program will generate test.pgm and test.yaml files and publish the grid map on the /grid_map topic.