This article explains what a slip is, why it occurs, how it impacts Hovermap operation, and what operators can do to prevent and respond to slips during flight.
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What is Slip?
A slip occurs when Hovermap completely loses localization. This happens when the system is unable to detect sufficient environmental features, or when there is inadequate overlap between scanned features to maintain positional tracking.
When a slip occurs, Hovermap can no longer reliably understand where it is in space, which directly impacts both mapping quality and autonomous behavior.
If a slip occurs, the following outcomes may be observed:
The resulting scan will not resemble the real-world environment and may appear as a distorted or scrambled line.
All autonomous functionality is lost, including the ability to hold position.
Return-to-home functionality is unavailable, as the system no longer knows where “home” is.
Feature Detection
Hovermap relies on detecting geometric features in the environment to localize itself. These features provide reference points that allow the system to understand movement and position over time.
Feature Overlap
Consistent overlap between previously scanned features and newly observed features is required to stitch the environment together. Without sufficient overlap, Hovermap cannot maintain localisation.
Why it matters
Slips directly impact both data quality and flight safety. When localization is lost, the scan data becomes unreliable, and autonomous flight behaviours are no longer available.
Understanding what causes slips allows operators to plan flights more effectively, avoid high-risk environments, and respond correctly if a slip occurs.
Key Benefits
Improved scan quality: Maintaining localization ensures scans accurately represent the real environment.
Safer operation: Preventing slips preserves autonomous stabilization and navigation functions.
Reduced rework: Avoids unusable datasets that require re-scanning or extended processing.
More predictable missions: Operators can confidently plan and execute flights in suitable environments.
How it works
Hovermap uses LiDAR data to continuously match observed features against previously scanned geometry. By comparing these features across time, the system estimates its position and orientation in space.
If the environment lacks distinguishable features, or if transitions between environments happen too quickly, Hovermap cannot correlate new data with existing data, resulting in a loss of localisation (a slip).
Common Scenarios
Slips most commonly occur in environments with limited geometric structure or poor LiDAR returns.
Open farmland, smooth tunnels, shafts, or other areas with minimal geometric variation can cause slips because everything appears the same to the system.
Water does not reflect LiDAR effectively, preventing Hovermap from detecting usable features and mapping the environment.
When Hovermap is flown too high, LiDAR points may not reach the ground with sufficient density to build a usable map.
Recommendation: Maintain a flight height of approximately 40 m.
Moving quickly between areas with different geometry, such as passing through doorways, hatches, or openings, can result in insufficient feature overlap. Without overlap between previously scanned features and new areas, localisation can be lost, increasing the risk of a slip.
Best Practices
Applying these best practices helps minimize slip and improve the accuracy and consistency of your scan results.
Do | Don't |
|---|---|
Maintain features in all directions (X, Y, and Z axes). | Fly over large bodies of water where features cannot be detected. |
Fly at recommended heights to ensure sufficient LiDAR density. | Move rapidly between distinct environments without overlap. |
Move slowly through transitions such as doorways and look back over previously scanned areas. | Operate in smooth, featureless spaces without introducing reference geometry. |
If a slip occurs:
Switch immediately to drone control mode.
Manually return the drone home safely.
Refer to the Emergency Procedures section for guidance.