docs: update elevation map loader readme (#785)

perception/elevation_map_loader/README.md

@@ -1,10 +1,10 @@
-# elevation_map_loader package
+# elevation_map_loader
 
-This package provides elevation map for compare_map_segmentation.
+## Purpose
 
-## elevation_map_loader
+This package provides elevation map for compare_map_segmentation.
 
-### Feature
+## Inner-workings / Algorithms
 
 Generate elevation_map from subscribed pointcloud_map and vector_map and publish it.
 Save the generated elevation_map locally and load it from next time.
@@ -16,23 +16,25 @@ Cells with No elevation value can be inpainted using the values of neighboring c
   <img src="./media/elevation_map.png" width="1500">
 </p>
 
-### How to run
-
-`ros2 run elevation_map_loader elevation_map_loader --ros-args -p param_file_path:=path/to/elevation_map_parameters.yaml -p elevation_map_directory:=path/to/elevation_map_directory -p pointcloud_map_path:=path/to/pointcloud.pcd`
+## Inputs / Outputs
 
-### Subscribed Topics
+### Input
 
-- input/pointcloud_map (sensor_msgs:PointCloud2) : PointCloud Map
-- input/vector_map (autoware_auto_mapping_msgs/HADMapBin) : binary data of Lanelet2 Map
+| Name                   | Type                                         | Description                                |
+| ---------------------- | -------------------------------------------- | ------------------------------------------ |
+| `input/pointcloud_map` | `sensor_msgs::msg::PointCloud2`              | The point cloud map                        |
+| `input/vector_map`     | `autoware_auto_mapping_msgs::msg::HADMapBin` | (Optional) The binary data of lanelet2 map |
 
-### Published Topics
+### Output
 
-- output/elevation_map (grid_map_msgs/GridMap) : Elevation Map
-- output/elevation_map_cloud (sensor_msgs:PointCloud2) : Pointcloud generated from the value of Elevation Map
+| Name                         | Type                            | Description                                                          |
+| ---------------------------- | ------------------------------- | -------------------------------------------------------------------- |
+| `output/elevation_map`       | `grid_map_msgs::msg::GridMap`   | The elevation map                                                    |
+| `output/elevation_map_cloud` | `sensor_msgs::msg::PointCloud2` | (Optional) The point cloud generated from the value of elevation map |
 
-### Parameter description
+## Parameters
 
-#### ROS parameters
+### Node parameters
 
 | Name                              | Type        | Description                                                                                                | Default value |
 | :-------------------------------- | :---------- | :--------------------------------------------------------------------------------------------------------- | :------------ |
@@ -50,17 +52,17 @@ Cells with No elevation value can be inpainted using the values of neighboring c
 | lane_filter_voxel_size_y          | float       | Voxel size y for calculating point clouds in vector_map [m]                                                | 0.04          |
 | lane_filter_voxel_size_z          | float       | Voxel size z for calculating point clouds in vector_map [m]                                                | 0.04          |
 
-#### GridMap parameters
+### GridMap parameters
 
 The parameters are described on `config/elevation_map_parameters.yaml`.
 
-##### General parameters
+#### General parameters
 
 | Name                                           | Type | Description                                                                                                  | Default value |
 | :--------------------------------------------- | :--- | :----------------------------------------------------------------------------------------------------------- | :------------ |
 | pcl_grid_map_extraction/num_processing_threads | int  | Number of threads for processing grid map cells. Filtering of the raw input point cloud is not parallelized. | 12            |
 
-##### Grid map parameters
+#### Grid map parameters
 
 See: <https://github.com/ANYbotics/grid_map/tree/ros2/grid_map_pcl>
 
@@ -73,9 +75,9 @@ Resulting grid map parameters.
 | pcl_grid_map_extraction/grid_map/height_type             | int   | The parameter that determine the elevation of a cell `0: Smallest value among the average values of each cluster`, `1: Mean value of the cluster with the most points` | 1             |
 | pcl_grid_map_extraction/grid_map/height_thresh           | float | Height range from the smallest cluster (Only for height_type 1)                                                                                                        | 1.0           |
 
-#### Point Cloud Pre-processing Parameters
+### Point Cloud Pre-processing Parameters
 
-##### Rigid body transform parameters
+#### Rigid body transform parameters
 
 Rigid body transform that is applied to the point cloud before computing elevation.
 
@@ -84,7 +86,7 @@ Rigid body transform that is applied to the point cloud before computing elevati
 | pcl_grid_map_extraction/cloud_transform/translation | float | Translation (xyz) that is applied to the input point cloud before computing elevation.                                  | 0.0           |
 | pcl_grid_map_extraction/cloud_transform/rotation    | float | Rotation (intrinsic rotation, convention X-Y'-Z'') that is applied to the input point cloud before computing elevation. | 0.0           |
 
-##### Cluster extraction parameters
+#### Cluster extraction parameters
 
 Cluster extraction is based on pcl algorithms. See <https://pointclouds.org/documentation/tutorials/cluster_extraction.html> for more details.
 
@@ -94,7 +96,7 @@ Cluster extraction is based on pcl algorithms. See <https://pointclouds.org/docu
 | pcl_grid_map_extraction/cluster_extraction/min_num_points    | int   | Min number of points that a cluster needs to have (otherwise it will be discarded).    | 3             |
 | pcl_grid_map_extraction/cluster_extraction/max_num_points    | int   | Max number of points that a cluster can have (otherwise it will be discarded).         | 1000000       |
 
-##### Outlier removal parameters
+#### Outlier removal parameters
 
 See <https://pointclouds.org/documentation/tutorials/statistical_outlier.html> for more explanation on outlier removal.
 
@@ -104,7 +106,7 @@ See <https://pointclouds.org/documentation/tutorials/statistical_outlier.html> f
 | pcl_grid_map_extraction/outlier_removal/mean_K             | float | Number of neighbours to analyze for estimating statistics of a point.          | 10            |
 | pcl_grid_map_extraction/outlier_removal/stddev_threshold   | float | Number of standard deviations under which points are considered to be inliers. | 1.0           |
 
-##### Subsampling parameters
+#### Subsampling parameters
 
 See <https://pointclouds.org/documentation/tutorials/voxel_grid.html> for more explanation on point cloud downsampling.