Control Points (Lixel P1)

Applicable device: Lixel P1 (PortalCam)

What Are Control Points

Control Points are a core feature added to the Lixel P1 to support multi-map fusion, mainly used to enhance spatial consistency between multiple map segments and improve the stability and accuracy of fusion reconstruction.

Control points apply to the following three fusion scenarios:

Placing the Device

When you need to add a control point during capture:

1. Open the PortalCam tripod and place the device stably at the location where you want to add a control point
2. The control point should be located in a well-lit, texture-rich, unobstructed open area as much as possible
3. After placing the device, it is recommended that the operator walk a full loop around the control point area to ensure 360° coverage of the surroundings, which significantly improves fusion algorithm stability

Position Accuracy for Shared Control Points

If a control point needs to be shared between multiple maps (for map fusion), the control point positions only need to be roughly consistent:

Control Point Placement for Different Fusion Scenarios

Map Fusion

Map fusion control point distribution (L-shaped, ≥3, spacing ≥10 m)

Aerial-Ground Map Fusion

• Control points should be set at the drone takeoff point
• The PortalCam orientation should be consistent with the drone camera direction
• Drone takeoff data must be placed in the same directory

Aerial-ground fusion control point distribution (set at the drone takeoff point)

Example data directory structure:

default_2025-11-02-142755/      # PortalCam project file
├─ project_data/
│  ├─ log/                      # Logs
│  ├─ model/                    # potree model files
│  ├─ photo/                    # Camera photos for the control point
│  ├─ control_points.csv        # Control point information
│  ├─ gnss.csv
│  ├─ poses.csv
│  └─ preview_photo.jpg
└─ 2025-11-02-142755.xbin

Drone/                          # Drone photo files
├─ DJI_202503191521_001/        # Aerial photo folder
│  ├─ image1/
│  ├─ image2/
│  └─ ...
├─ DJI_Link_1/                  # Vertical takeoff/landing photo folder
│  ├─ image1/
│  ├─ image2/
│  └─ ...
└─ ...

HD Enhancement

• Control points should be located in the enhancement area and face the direction to be enhanced
• The first frame of HD Enhancement should start from directly above the control point
• The corresponding enhancement data must also be placed in a single directory

HD Enhancement control point distribution (located in the enhancement area, facing the target)

Adding a Control Point

1. After placing the device stably, open the capture interface of the LCC Scan App
2. Select the "Add Control Point" function
3. Set the control point attributes:

4. Select the corresponding control point type based on the actual scenario
5. After creation, the system synchronously records position, direction, and other information

⚠️ Note: Do not power off within 5 seconds of adding a control point, to avoid losing the control point file.

Considerations

• Ensure there is no obstruction within the control point's field of view
• Avoid direct strong light on the control point location to reduce positioning error
• Walk a full loop around the control point after placement (360° coverage)
• The position and orientation of same-name control points across different maps should be roughly consistent