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Author Topic: indoor scanning  (Read 2580 times)

pesho

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indoor scanning
« on: May 29, 2018, 07:50:31 AM »
Hello everybody!
I need some help, can you tell me how to get all of the photos of room with dimensions: 10m long, 3,5 m wide, 4m high. I want to get nice model with detected markers evenly distributed across all walls?

Dave Martin

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Re: indoor scanning
« Reply #1 on: May 29, 2018, 12:04:50 PM »
Pesho,

Suggest you read the manual and especially take note of the 'interior' diagrams at the top of page 10.

Dave

Smallpoly

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Re: indoor scanning
« Reply #2 on: May 30, 2018, 09:52:33 PM »
For the shoot locations, the goal is to maximize parallax while still having good overlap. Markers are great, and help deal with the "blank white walls" problem of anything built in the modern era.

Link to the manual: http://www.agisoft.com/pdf/photoscan-pro_1_4_en.pdf

This is the diagram Dave is referring to.


Text from the docs:
Quote
• Number of photos: more than required is better than not enough.
• Number of "blind-zones" should be minimized since PhotoScan is able to reconstruct only geometry
visible from at least two cameras.
In case of aerial photography the overlap requirement can be put in the following figures: 60% of side
overlap + 80% of forward overlap.
• Each photo should effectively use the frame size: object of interest should take up the maximum area.
In some cases portrait camera orientation should be used.
• Do not try to place full object in the image frame, if some parts are missing it is not a problem providing
that these parts appear on other images.
• Good lighting is required to achieve better quality of the results, yet blinks should be avoided. It is
recommended to remove sources of light from camera fields of view. Avoid using flash.
• If you are planning to carry out any measurements based on the reconstructed model, do not forget to
locate at least two markers with a known distance between them on the object. Alternatively, you could
place a ruler within the shooting area.
• In case of aerial photography and demand to fulfill georeferencing task, even spread of ground control
points (GCPs) (at least 10 across the area to be reconstructed) is required to achieve results of highest
quality, both in terms of the geometrical precision and georeferencing accuracy. Yet, Agis

SAV

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Re: indoor scanning
« Reply #3 on: May 31, 2018, 07:11:59 AM »
Hi pesho,

Here are a few useful tips and tricks:
1. Use a prime lens with a relatively small focal length (e.g., 16mm on APS-C) to ensure a sufficient image overlap.

2. Use a digital camera (DSLR or mirrorless) with an APS-C or full frame sensor

3. Collect imagery at two different height levels, e.g. one photograph kneeing down and another one shot holding the camera above your head.

4. Make sure the room is well lit.

5. Manually set the white balance on your camera.

6. If you can cover transparent areas such as windows then do so before acquiring the imagery. Otherwise you won't be able to reconstruct these areas.

7. Use coded markers (TOOLS > MARKERS > PRINT MARKERS). Will make your life much easier... and they are actually more accurately picked by the algorithm compared to a manual workflow.

All the best.

Regards,
SAV

James

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Re: indoor scanning
« Reply #4 on: May 31, 2018, 03:23:33 PM »
This is the diagram Dave is referring to.


Don't follow that diagram blindly though. Note that none of the suggested shots in 'correct' are actually pointing into the corners of the room. If the room is large enough then you may get better results by reversing the direction of the arrows!

4. Make sure the room is well lit.

Easier said than done, see attached! Also don't forget to watch out for the priceless artefacts...
« Last Edit: May 31, 2018, 03:29:42 PM by James »