Course 1 - Lesson 7
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Most properties can be captured in a single 20-minute session. But larger buildings - big commercial sites, multi-storey blocks, warehouses - require more time than a single session allows. This lesson explains how to split a capture across multiple sessions so that photogrammetry can still stitch everything together into one accurate model.
When one capture is not enough
If you expect a full site capture to take longer than 20 minutes, plan from the start to split it into multiple sessions. Do not try to rush a 40-minute building into one take. Attempting to capture too much in one session creates too many images, slows processing significantly, and risks running out of battery or storage mid-capture. Plan your split points before you arrive on site.
The overlap rule
This is the most important rule for multi-capture buildings. When you restart a capture after ending a previous session, you must begin walking 2 to 3 metres back along the path you already covered before starting the new recording.
Why? Photogrammetry works by matching visual features across images. For two separate sessions to join into one model, the algorithm needs overlapping images that appear in both sessions. Without that overlap, the two sessions cannot be stitched together and you will end up with disconnected data.
A 2 to 3 metre walkback into the previous session's territory gives the algorithm enough shared frames to make the join reliably. Do not start from exactly where you stopped.
Pausing in a large room
If you are going to spend a significant amount of time in a single large room or open space, do not record continuously for the entire time. Recording 10 or more minutes of the same area creates a large number of near-identical images that slow processing without improving the model.
Instead, pause the capture in the centre of the room, then restart it in the centre of the room. This keeps the session length manageable and avoids the processing overhead of redundant images. Apply the same overlap rule: when you restart, walk a short distance back into territory you already covered before beginning your new path.
Planning a multi-capture site
Before you start, walk the route in your head and identify natural split points. Good split points are: doorways between wings or floors, the top of a staircase, the threshold between interior and exterior. Avoid splitting mid-corridor or in the middle of a long featureless space - those transitions give the algorithm less to work with. Split at transitions between distinct areas.
Target boards across sessions
Target boards must not be moved between capture sessions. If you placed your A board at the entry and your B board at the far end of the site, both must remain in those exact positions throughout every session. The boards anchor the scale for the entire model. Moving them between sessions breaks that anchor and can produce incorrect measurements.
Check battery and storage before each session so you do not run out mid-capture. Do not request processing until all sessions for the site have been uploaded.
Multi-capture checklist
1. Split points identified and noted before arrival
2. Target boards placed and confirmed in position before session 1 starts
3. For each new session: start 2 to 3 metres back into previously captured territory
4. For large rooms: pause and restart in the centre rather than recording continuously
5. Target boards have not moved between sessions
6. Battery and storage checked before each session
7. All sessions uploaded before requesting processing
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Previous lesson: 1.6 - Uploading Your Capture & What Happens Next