docs: update document for dataset schema

README.md

@@ -8,7 +8,9 @@ A toolkit to load and operate T4 dataset.
 
 ## Getting started
 
-📘 [Documentation](https://tier4.github.io/t4-devkit/) |
+<!-- TODO(ktro2828): 📝 [Dataset Schema](https://tier4.github.io/t4-devkit/schema) | -->
+
+🏠 [Documentation](https://tier4.github.io/t4-devkit/) |
 ⚙️ [Tutorial](https://tier4.github.io/t4-devkit/tutorials/initialize/) |
 🧰 [API Reference](https://tier4.github.io/t4-devkit/apis/tier4/)
 
@@ -46,10 +48,6 @@ The virtual environment can be activated with:
 source .venv/bin/activate
 ```
 
-## Dataset Format
-
-For details of T4 dataset format, please refer to [tier4_perception_dataset/t4_format_3d_detailed.md](https://github.com/tier4/tier4_perception_dataset/blob/main/docs/t4_format_3d_detailed.md).
-
 ## Feature supports
 
 ### Visualization

docs/index.md

@@ -6,10 +6,6 @@
     <img src="assets/render_scene.gif" width="800" alt="RENDER SAMPLE"/>
 </div>
 
-## Dataset Format
-
-For details of T4 dataset format, please refer to [tier4_perception_dataset/t4_format_3d_detailed.md](https://github.com/tier4/tier4_perception_dataset/blob/main/docs/t4_format_3d_detailed.md).
-
 ## Feature supports
 
 ### Visualization

docs/schema/data.md

@@ -0,0 +1,84 @@
+# Sensor Data
+
+## LiDAR Point Cloud
+
+LiDAR directory contains point cloud data as the name of `<LIDAR_CONCAT>` or `<LIDAR_TOP>`:
+
+```shell
+data/
+└── LIDAR_CONCAT
+    ├── <FRAME_ID>.pcd.bin
+    ...
+```
+
+Each file contains `(x, y, z, intensity, ring_idx(=-1))`, and location coordinates are given with respect to the ego vehicle coordinate system.
+
+Each file can be loaded using as follows:
+
+```python
+# Using NumPy
+import numpy as np
+
+def load_lidar_point_cloud(file_path) -> np.ndarray:
+    data = np.fromfile(file_path, dtype=np.float32) # (N*5,)
+    return data.reshape((-1, 5)) # (N, 5)
+
+# Using t4-devkit
+from t4_devkit.dataclass import LidarPointCloud
+
+def load_lidar_point_cloud_t4(file_path) -> LidarPointCloud:
+    return LidarPointCloud.from_file(file_path)
+```
+
+## Camera Image
+
+Camera directory contains raw images as the name of `<CAM_XXX>`:
+
+```shell
+data/
+├── CAM_BACK
+│   ├── <FRAME_ID>.jpg
+│   ...
+├── CAM_BACK_LEFT
+├── CAM_BACK_RIGHT
+├── CAM_FRONT
+...
+```
+
+## Radar Object
+
+Radar directory contains radar object tracks
+
+```shell
+data/
+├── RADAR_BACK
+│   ├── <FRAME_ID>.pcd
+│   ...
+├── RADAR_BACK_LEFT
+├── RADAR_BACK_RIGHT
+├── RADAR_FRONT
+...
+```
+
+Each file is based on NuScenes radar data format as follows:
+
+```shell
+# .PCD v0.7 - Point Cloud Data file format
+VERSION 0.7
+FIELDS x y z dyn_prop id rcs vx vy vx_comp vy_comp is_quality_valid ambig_state x_rms y_rms invalid_state pdh0 vx_rms vy_rms
+SIZE 4 4 4 1 2 4 4 4 4 4 1 1 1 1 1 1 1 1
+TYPE F F F I I F F F F F I I I I I I I I
+COUNT 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
+WIDTH 112
+HEIGHT 1
+VIEWPOINT 0 0 0 1 0 0 0
+POINTS 112
+DATA binary
+```
+
+```python
+from t4_devkit.dataclass import RadarPointCloud
+
+def load_radar_point_cloud(file_path) -> RadarPointCloud:
+    return RadarPointCloud.from_file(file_path)
+```

docs/schema/index.md

@@ -0,0 +1,41 @@
+# Dataset Schema
+
+## Directory Structure
+
+```shell
+<DATASET_ID>/
+└── <DATASET_VERSION>
+    ├── annotation    ...schema tables in JSON format
+    ├── data          ...sensor raw data
+    ├── input_bag     ...original ROS bag file
+    ├── map           ...map files
+    └── status.json   ...dataset status information
+```
+
+## Schema Tables
+
+Annotation information is stored in the `annotation` directory.
+
+See [the document of dataset schema](./table.md) for details.
+
+## Sensor Data
+
+Raw sensor data is stored in the `data` directory.
+
+See [the document of sensor data](./data.md) for details.
+
+## Map Data
+
+Map data is stored in the `map` directory.
+
+It is structured as follows:
+
+```shell
+map/
+├── lanelet2_map.osm
+└── pointcloud_map.pcd
+```
+
+## status.json
+
+`status.json` contains the information about the configuration used to generate the dataset.