Introduction

Use this guide when your route runs through confined spaces, such as narrow corridors, tunnels, service shafts, or tight stairs, where standard scanning patterns strain accuracy and safety. You'll need a planned path with safe entry and exit points; by the end, you'll have full coverage through the narrow spaces.

Scanning Narrow Corridors and Tunnels

1. Walking the corridor

1. Follow a steady path
   Walk slowly along the corridor, either on the center line or slightly off-center.

2. Keep both walls in view
   Avoid walking very close to one wall only. In some areas, it can help to walk at a slight angle instead of perfectly straight, so the sensor sees more geometry of the corridor. 

3. Move steadily, especially at corners
   At corners, turn in wide, gentle curves instead of quick spins or sharp pivots.

   1. Do not insert NavVis MLX into spaces narrower than 1 m in diameter.

   2. In very tight spots (such as small toilet cabins), hold the device horizontally so it scans ceiling and floor while you rotate. This ensures the laser scanner always see enough geometry, even if the walls are very close.

4. Turn the device
   Every few meters, rotate the device slightly, without sudden movements so both walls are visible to the device.

5. Tilt to show upper walls and ceiling
   From time to time, tilt the device slightly so it captures upper walls and ceiling, not only the floor.

   3. If you need to, go back and forth in the corridor and begin and end at a well‑defined spot (for example, at a junction or a wider area). Avoid repeatedly turning around in very tight spots as this can affect the data quality.

      Scanning Narrow Stairs

      1. Before you step on the stairs

      1. Approach the staircase with NavVis MLX secured in its harness.

      2. Before stepping on, scan as much of the staircase as possible.

      2. At the top landing

      1. At the top, scan the upper floor area before descending.

      3. Going down the stairs

      4. Hold the device horizontally and keep one hand on the handrail for safety.

      5. Go up and down the staircase for full data coverage.

      Post‑Scanning Quality Checks

      1. Check scan coverage 

      Check scan coverage on the quality map. If you see dark or grey areas, slow down and expose the laser scanners to those areas. Keep scanning until they turn solid bright blue.

      2. Check problem areas

      3. Look closely at:

         • Long, plain corridors for unexpected bends or twists.

         • Transitions between stairs and corridors on each floor for vertical alignment issues.

         • Transitions between stairs and corridors
           Pay close attention to transitions between stairs and corridors on each floor, where alignment problems may appear. If you see issues, immediately go back and forth in those areas with slow, smooth motion to strengthen the trajectory.

           3. Targeted rescan if needed
              If you see problems, plan a short follow-up scan that focuses on the affected junctions, landings, or stair sections. During this rescan, move slowly and use clear connections (for example, landings and junctions) to strengthen loop closure.