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Author Topic: Marker detection (Treshold size?)  (Read 1849 times)

indesinenter

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Marker detection (Treshold size?)
« on: September 20, 2019, 03:51:15 PM »
Hello,  :)

I am trying to calibrate different cameras with Agisoft Methashape, but I have problems with the automatic detection of markers. Could there be some sort of limiting size / pixels? I find that when the marker (in pixels) is larger than a threshold Methashape does not detect the marker. Can this threshold be modified?

Any help will be appreciated, since I can not make the calibration photos again because the cameras are installed in an inaccessible area.

Attached are two screenshots showing how markers are identified only from a certain distance from the camera. (when the size of the markers is less than a threshold)

Thanks!

indesinenter

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Re: Marker detection (Treshold size?)
« Reply #1 on: September 22, 2019, 02:15:58 PM »
Hi!

I have been working more on this, and I made a comparison with the same picture (and obviously same relation marker/picture) but with different pixel dimensions. One is 7952 x 5394 (42Mpx) and the other one is 3976 x 2652 (10.5Mpx) (I reduced 50% pixel sizes).

The result is that Marker Detection did not identify any markers in the original image but did identify 20 markers in the reduced image. This leads me to think that there is a maximum internal size (in pixels, not in relation marker/image) for markers that can be detected.

Now that it is easy to have pictures with enough megapixels (more than 24), could it be possible to have access to change this parameter?

And, I suppose that the calibration parameters that I obtain with the reduced image aren't equivalent with the original size? Because the parameters are related with the pixel size of the image?

Thanks!