Capturing a Scan
Site captures are organised according to a hierarchy of projects, scenes, and scans. For example, a project might represent the entirety of a building. Each scene within that project might represent one floor within that building. Each scan provides a single time-stamped capture of that scene on a particular day.
When capturing data of a scene we refer to this as "scanning" the scene. A scan is one continuous walk through the entire scene. Sensori Capture is able to stitch together multiple separate recordings, but only if they contain significant amounts of overlap with each other.
Order of operations
Ensure there is a memory card and charged battery in the camera before going to the site
Locate surveyed control points if those will be used
Place control point targets over surveyed control points and note the target ID used for each point.
Distribute scale plates around the scene. They do not need to be horizontal, so leaning them against a wall can improve visibility.
If not using a supported 360 camera, place the origin plate horizontally at a desired 0,0,0 position.
Turn the camera on
Optionally connect the Sensori app for approximate georeferencing if using an Insta360 camera.
Set the camera to the highest resolution video mode if not using the app.
Start recording.
Slowly walk through and capture the scene, making sure to regularly turn around a full 360 degrees on the spot. This is still important when using a 360 camera.
Take care to record each target more than once and try to get within less than 1 metre of the target. Turning the camera around in front of the scale plates will help with calibration for improved accuracy.
Walk back to where you started if possible and try to revisit locations to improve loop closure.
Stop recording
Collect targets as required
Upload videos from camera and control points csv file if used to the Sensori website or via the app.
Walking the site
When capturing there are a few guidelines to consider:
Don't move faster than a slow walk, about a third your usual pace
Don't swing the camera faster than you would a cup of liquid
Each time you pass a scale plate, bring the camera close to it and wave the camera around slowly while turning it so both lenses face the target. This is not critical, but will improve accuracy.
Try to "weave" through the site, crossing back over spaces you have walked through
Occasionally turn around a full 360 degrees on the spot to ensure you capture in all directions. This is very important to ensure your capture is fully connected and has low drift error. You should still do this when using a 360 camera.
If a space becomes narrow, such as a tight corridor or doorway, then slow your pace further
If there are areas of interest (pipes, cables, etc) then get closer to these areas and slowly move the camera around them to capture more detail
Any area that you don't walk through will not be reconstructed well, so be sure to walk throughout the whole scene that you want to capture. It doesn't matter where you start, but it's a very good idea to walk back to where you started before you end the capture, and try to visit each area more than once
Examples showing good capture technique in a small outdoor area
Starting recording using the Sensori Android app and an Insta360 X5 camera. You can also start recording using the normal camera controls:
Occasionally turn around to help with calibration:
Wave the camera slowly in front of the scale plates while turning for improved accuracy:
Example walking path while capturing:
The resulting processed scan inside the Sensori viewer:
Because the Sensori app was used, the scan will be approximately georeferenced. Here is the generated geotiff ortho image over an aerial imagery base layer:
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