SLAM stands for Simultaneous Localization And Mapping. SLAM technology runs in real-time to allow Hovermap to create a map of its environment, while at the same time working out its position, orientation, and speed within that environment.
Emesent capture devices use this technology for a variety of tasks, including mapping, autonomous navigation, collision avoidance, and position hold in GPS-denied environments.
SLAM relies on distinct geometric features to work effectively. Using these features, Hovermap can build a map of its surroundings and track them as it moves around. This means that there is no need for external infrastructure, such as GPS. As a result, Hovermap can work outdoors, indoors, and underground.
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GPS vs SLAM
Just as you need many GPS satellites to have a good GPS location, SLAM needs recognizable features to calculate a good position.
Why are features important?
For SLAM to work, it requires features to be present in its surroundings. Features are distinct geometric objects that do not move. Hovermap uses these features to determine its position in space and to build a point cloud around itself.
Feature-rich environments are ideal for SLAM, but smooth, featureless environments can present a challenge. If you use Hovermap in a featureless environment, you run the risk of a SLAM slip. This means that Hovermap will completely lose track of its surroundings, which will affect autonomous functionality, ruin your scan, and potentially damage your Hovermap (for more information, refer to the What is a slip? section). This is why an understanding of how Hovermap sees the world is so important.
Feature-rich environments
Feature-rich environments contain many distinct, geometric features that do not move. These environments are ideal for Hovermap. A good example is a city center, with large, distinct buildings that can help Hovermap track itself. In this environment, Hovermap is able to operate both more effectively, and at a greater height, than it would be able to in a sparser environment.
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Challenging environments
Environments without distinct geometric features can be more challenging for Hovermap to navigate. There are certain techniques available to help you produce more reliable scans in these environments, but you will need to be mindful of your surroundings and plan your scan carefully in order to avoid a SLAM slip.
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Examples of challenging environments include:
Flat and smooth areas without features, such as large outdoor parking lots, sports fields, and lakes.
Smooth tunnels or passageways with featureless walls, such as inside concrete water pipes.
Areas with very similar and repetitive features and patterns.
Areas dominated by vegetation, such as forest canopies, gardens, and parkland (where the features all look the same, forming a homogenous surface).
Environments with many moving objects, such as cars, trucks, and plant machinery.
Environments with many features that can absorb or reflect LiDAR beams, such as water or dark, matt paints.
Environments that require you to transition through very narrow passages.
It is best to avoid scanning in completely featureless environments, as Hovermap will not be able to track itself. However, you can introduce your own features (such as pylons and parked vehicles) to these environments to make them more SLAM-friendly. These introduced features should be geometric if possible, and not able to move. Bear in mind that markings and colors are not features. Features are objects.
Featureless environment with smooth, uniform surfaces | Environment with highly repetitive features and similar patterns |
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It's complicated
Tips for working with features
Make sure that there are always enough features within 40 m of Hovermap. The closer they are, the better.
Keep any features in front of Hovermap as much as possible.
Where possible, add features to smooth environments.
Fly as low and as slow as possible.
Avoid scanning in areas with lots of moving objects.
Move Hovermap so that it can continuously see where it has been and where it is going. This is especially important when you move through narrow passages and doorways.