Sample Units Generator
Function Description: A sample unit is the basic spatial unit for PCI calculation. It defines the pavement included in the evaluation and divides a continuous road into sections for statistics. Accurate sample units prevent distress outside the pavement from being included and valid pavement from being omitted. Results are generated in the "Sample Unit" layer.
Input Data
Automatic Mode: Requires a point cloud covering the road and the corresponding trajectory. Pavement boundaries are determined by detecting curb positions on both sides of the trajectory
Fixed Width Mode: Requires Lane Line vectors and constructs the road range from lane width and left and right lane counts
When ground classification is available, select the ground class for curb detection in Automatic Mode.
Operation Steps
1.Click Sample Units Generator to open the settings dialog
2.Select Automatic Mode or Fixed Width Mode
3.Set the corresponding parameters and click OK to generate sample units
4.Check the coverage and boundary continuity of the "Sample Unit" layer. If a boundary is inaccurate, use Sample Units Editor to correct it
Generation Modes
The mode depends on the available road boundary data. Use Automatic Mode when curbs on both sides are clear and the trajectory is reliable. Use Fixed Width Mode when curbs are unclear but Lane Line data is reliable. Before generation, confirm that the input data required by the selected mode is loaded.
| Mode | Description |
|---|---|
| Automatic Mode | Automatically detects curb positions from the trajectory and point cloud and divides sample units along the road. Suitable for roads with clear boundary features |
| Fixed Width Mode | Builds a fixed road range from Lane Line data, lane width, and left and right lane counts. Suitable when reliable Lane Line data is available or curbs are unclear |
Parameter Settings
Automatic Mode
| Parameter | Description |
|---|---|
| Source Class | Point class used for curb detection |
| Minimum Lane Width | Minimum lane width used to limit automatic road boundary detection |
| Maximum Lane Width | Maximum lane width used to limit automatic road boundary detection |
| Sample Unit Area | Standard area used to divide units. The default is 255 m² |
Fixed Width Mode
| Parameter | Description |
|---|---|
| Select | Select a Lane Line vector layer, or pick an individual Lane Line vector from the layer |
| Clear | Clears the selected vector layer or vector |
| Lane Width | Standard lane width |
| Left Lane Count | Number of lanes on the left side of the Lane Line, based on the line direction from start point to end point |
| Right Lane Count | Number of lanes on the right side of the Lane Line, based on the line direction from start point to end point |
| Sample Unit Area | Standard area used to divide units. The default is 255 m² |
Automatic Mode automatically removes duplicate round-trip trajectories. After generation, manually check the sample units, especially at intersections, road-width transitions, and areas with unclear boundary features.
Output Results
The generated results are stored in the "Sample Unit" layer. They define the pavement area included in the evaluation and serve as input for PCI calculation.
Result Check
Check whether sample units continuously cover the target pavement, include obvious non-pavement areas, or contain broken or shifted boundaries. If a problem is found, use Sample Units Editor to correct it before calculating PCI.