Slam Technique

How to Use Slam Eagle Properly: A Simple Guide to SLAM Scanning (Explained Step by Step)

If you are using Slam Eagle for 3D surveys, you already know that it is designed to be fast, portable, and easy to use. However, to obtain clean, accurate, and reliable point clouds, it is important to understand how SLAM scanning really works and to follow a few practical rules during data acquisition.

In this guide—written in a clear, practical, “Aranzulla-style” approach—I’ll explain how to scan correctly with Slam Eagle, what to avoid, and how to get the best results even in complex environments.

How Slam Eagle Scans Space: the Key Concept You Must Know

The Slam Eagle LiDAR sensor is not parallel to the ground.
Instead, it is mounted at an inclined angle with respect to the imaginary acquisition plane (the plane parallel to the ground).

This design allows the LiDAR beam to continuously intersect the floor while moving forward, effectively “slicing” the surrounding space.
You can imagine the scan as a rotating lamp: everything that is illuminated is acquired, everything that is not illuminated is not recorded.

This simple concept explains many behaviors of SLAM scanning.

Correct Operator Position: Why Height and Orientation Matter

During acquisition, Slam Eagle is meant to be used dynamically:

  • hold the device in the direction of your gaze
  • keep it perpendicular to your chest
  • position the display at eye level

This configuration allows the cylindrical scanning volume to extend above the operator’s head.
The result is:

  • reduced noise
  • better coverage
  • acquisition of the space behind the operator

Incorrect positioning can limit the scanned volume and degrade data quality.

Understanding Cylindrical SLAM Acquisition

SLAM systems acquire data inside a cylindrical volume around the device.
Once you understand this, it becomes much easier to deal with special scenarios such as staircases.

How to Scan Stairs Without Missing Data

A common mistake is scanning downstairs while pointing the device forward.
In this case, part of the staircase remains outside the illuminated volume, producing dark (missing) areas in the point cloud.

Correct approaches are:

  • scanning the stairs while going up
  • or scanning while going down but pointing Slam Eagle toward the scanned surface, paying attention to safety

Remember: if the LiDAR beam doesn’t see it, the data doesn’t exist.

Wrist Movement: A Small Detail That Improves Accuracy

When scanning a room, the best practice is:

  1. enter the room
  2. reach its center
  3. rotate around your wrist, not your whole body
  4. exit the room

The correct motion is a controlled rotation around the handle.

This minimizes unnecessary movement, reduces oscillations, and limits disturbances to the inertial platform, improving overall SLAM stability and reducing acquisition time.

What the Inertial Platform Does (and Why Initialization Is Critical)

At the heart of SLAM technology is the inertial reference system (IMU).
This system defines the origin and orientation of the acquisition coordinate system.

During the initialization phase, Slam Eagle must be:

  • reasonably still
  • stable
  • parallel to the acquisition plane

For this reason, a mini tripod mount is provided under the handle. Using it allows you to place the device on a flat surface and wait for proper inertial initialization without introducing unwanted motion.

A poor initialization affects the entire scan.

Drift, Time, and Earth Rotation: The Real SLAM Limitation

SLAM scans are perfectly coherent with their starting point, but over time they are influenced by:

  • inertial drift
  • Earth’s rotational dynamics

This does not affect local accuracy but introduces time-dependent drift.

In practice:

  • relative errors are negligible
  • drift increases with acquisition duration

That’s why scan planning is essential.

Should You Always Return to the Starting Point?

Many SLAM workflows suggest returning to the starting point to close the loop and let software handle correction.
This is valid—but not always optimal.

A more efficient strategy is to:

  • plan short, ordered scans
  • limit acquisition to a few minutes per scan
  • merge multiple scans into a single model if needed

Thanks to SLAM’s high productivity, this approach keeps drift under control while maintaining high accuracy.

Practical Example: Scanning a Large School Building

A recommended workflow is:

  1. External scan
    • define the building envelope
    • fast perimeter path
    • easy verification of loop closure
  2. Internal scans
    • rooms and corridors acquired separately
    • simple alignment inside the calibrated envelope

This method produces a clean, controlled, and reliable final model.

Georeferencing Slam Eagle with GNSS (RTK and PPK)

Slam Eagle supports RTK and PPK georeferenced surveys.
By integrating GNSS solutions such as the GPS ProTrack by Analist Group, it is possible to:

  • anchor SLAM data to absolute coordinates
  • compensate drift
  • integrate SLAM surveys with traditional topographic data

This is especially valuable for professional and engineering-grade workflows.

Final Thoughts

Slam Eagle is simple to use, but understanding how it works is what allows you to achieve professional results.

If you remember:

  • cylindrical acquisition
  • correct operator posture
  • controlled wrist movement
  • proper inertial initialization
  • smart scan planning

you will consistently produce clean, accurate, and reliable point clouds ready for real-world applications.