During a SLAM survey, the scanner continuously estimates its position and orientation while building the point cloud. As the survey progresses, small positioning errors may accumulate along the scanning path, resulting in drift. In the final point cloud, this may appear as double walls, misaligned structures, or distorted corridors.

One way to reduce accumulated drift is through loop closure. When the scanner returns to an area that has already been scanned, the system can recognize and match previously captured features with the current observations. This creates a connection between different parts of the scanning trajectory and helps correct accumulated positioning errors.

For example, you may start a survey in a lobby, continue through several corridors and office areas, and eventually return to the same lobby. Features such as door frames, wall corners, and pillars captured both at the beginning and end of the survey can help the system recognize that it has returned to a previously scanned area. These repeated observations provide the reference needed for loop closure.

How to Plan Your Scanning Path

A well-planned scanning path can provide more opportunities for loop closure and improve the overall quality of the point cloud.

1. Start from an Area with Distinctive Features

Choose a starting area with clear and stable geometric features, such as wall corners, door frames, pillars, or other structures that are easy for the scanner to recognize.

These features can serve as useful references when you return to the starting area later.

2. Include Revisited Areas in the Route

For larger projects, plan the route so that you return to previously scanned areas instead of continuously moving into new areas without revisiting them.

Corridors, intersections, entrances, and open spaces can be useful locations for creating loop closures.

3. Maintain Sufficient Overlap

When revisiting an area, make sure that previously scanned features are captured clearly again. Sufficient overlap between the earlier and current observations gives the system more information for matching the two scanning segments.

4. Move Smoothly at Key Locations

Pay particular attention when passing through doorways, corners, and other areas where the scanning environment changes significantly. Moving too quickly may reduce the quality of the observations available for positioning.

Slow down when passing these areas and allow the scanner to capture enough environmental features.

Consider Lighting Conditions When Planning the Route

In addition to the scanning path itself, lighting conditions should also be considered when planning a SLAM survey.

SLAM devices that use cameras rely on visual information to help estimate movement and recognize environmental features. Sudden changes in lighting or very strong light sources can affect image quality. For example, pointing the camera directly toward a bright window or light source may cause overexposure, making surrounding features difficult to recognize.

Before scanning, check the lighting conditions along the planned route and make adjustments where possible:

• Dim areas: Turn on available lights or open windows to provide sufficient illumination.

• Overly bright areas: Close curtains or windows where possible to reduce excessive light.

• Strong direct light: Avoid pointing the camera directly toward intense light sources when scanning.

• Large lighting changes: Where possible, plan the route to avoid abrupt transitions between very dark and very bright areas.

Maintaining relatively consistent and sufficient lighting helps the cameras capture clearer visual information throughout the survey.

Plan the Route Before You Scan

A good SLAM survey is not only about how the scanner is operated during the scan. Route planning also plays an important role in the final point cloud quality.

By selecting distinctive starting areas, incorporating revisited sections, maintaining sufficient overlap, and considering lighting conditions in advance, you can provide the SLAM system with better environmental information for positioning and loop closure.

These simple preparations can help reduce accumulated drift and produce a more consistent and reliable point cloud, especially in large or complex indoor environments.