Filtering is an automated algorithm and is not perfect. We recommend using either the No Filter or Equipment filter and combining this with the Terrain Cleanups tool to ensure you only remove items that would affect measurements onsite. If you have been using an Advanced filter and are satisfied with the results, please feel free to continue using it.
How does it work?
A point cloud is a collection of points in a 3D coordinate system, where each point represents a specific location in space, depicting objects or terrain. When processing drone imagery, each pixel in the images is assigned coordinates (X, Y, and Z). After stitching the images together, these pixels are transformed into 3D point clouds of varying densities, recreating the area you surveyed. Filtering involves grouping points in the point cloud into classes based on their characteristics. These grouped points can be excluded from the final elevation model if necessary.
For a point to be classed as something other than “ground,” it has to meet all three of these criteria:
- Point Distance (m): This measurement limits a point's distance from the ground. The greater the distance, the more likely the point is to belong to a raised obstruction.
- Hold Size (m): Defines an area in which groups of points should be left untouched. This value can vary from a stockpile to a large building.
- Point Angle (degrees): This defines a line between the ground and a raised feature. The greater the angle, the more likely the point is to belong to a vertical feature.
How to choose the best filter for your survey
Filtering obstructions on site is essential to monitoring assets and job progress. Whether it’s a shrub impeding a calculation of bare earth or a vehicle parked on a surface you want a gradient read on, filters help minimize such obstructions. Think about the current obstructions you are most concerned about affecting your data onsite. The list below gives you an idea of what we can filter from your 3D surveys. When choosing a filter, remember that bare earth can only be rendered where the camera can see it. If the camera cannot see it, the filtering will eliminate as much obstruction as possible but may not provide a completely flat surface below.
No filter
Equipment
The best filter to choose if there are stockpiles you are measuring onsite. It removes anything up to and including the size of vehicles, haul trucks, or conveyors. It is unlikely to affect stockpile volumes.
Equipment and vegetation
Removes everything the Equipment filter removes, plus everything up to and including large trees. This can also include the tops of stockpiles. You’ll see bare earth underneath trees, shrubs, etc. The exception is when the vegetation is dense enough that the camera cannot see the ground over a large area.
Equipment, vegetation, and structures
Removes everything the above filters remove, plus everything up to and including the size of large structures and buildings.
Everything
This removes stockpiles entirely and everything else to produce a “bare earth” model. It cannot filter large areas of dense vegetation where the ground is not visible to the camera. Only use this filter on flat sites.
I still can't do it!
We wrote these articles to equip you with everything you need to get the job done on your own, but we understand that sometimes this isn't sufficient.
If you're stuck, you can connect with our support team by clicking the support button on the top right corner of your user portal.
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