Topics

1

General / Matches listed in console but not in "View Matches"

« on: February 25, 2021, 12:08:51 PM »

Hi,

I can not get the Photo Alignment to work, because Metashape does not find any matches between the images. The weird thing is that the console (or the log file) says that many hundreds of thousands of matches are found, however, the alignment fails and when I click on "View Matches" I see that most images have no matches at all. Just a few images have up to 10 matches and they are all marked as invalid. I knew the issue of having thousands of matches that are marked as "Invalid" in  the "View Matches" window, but in this case I don't even have invalid matches. I can't explain at which steps I lost all the matches that are mentioned in the console. I attached a screenshot to clarify my situation.

I am using 28 sets of Photos from 4 DSLR cameras that I use as a Multi-Camera-System (i.e. I have 4 sensors and 28 cameras). The images are from a calibration board that I believe to be suitable for matching in Metashape, as it contains a lot of texture.

Thanks in advance for any help! 

2

General / Reprojection Error: Gradual Selection vs. Chunk Info

« on: August 19, 2020, 04:27:39 PM »

Sorry to dig up this old question again. I thought I had understood the reprojection error, but when trying to remove tie points with bad reprojection errors I saw that the RMS reprojection error from the chunk info was very different from the biggest reprojection error shown under gradual selection.

I understand that the reprojection error is the distance in pixels of the reprojected tie point to the respective key point on an image.

As you can see in the attached figure, the RMS Reprojection error in the chunk info is 2.46 pixels. But when I go to gradual selection and choose "Reprojection error", the largest value where any tie points are selected is "Level 0.84". I would have expected the gradual selection value to be higher.

My best guess for why this is, would be that the Reprojection Error "Level" in the Gradual selection dialogue doesnt refer to the original image resolution but a downscaled version of the image. Or maybe the two values are calculated over a different range of tie points?
Could you please explain why these values are so different?

3

Camera Calibration / Principal point coordinates always 0 in Inpho.prj file

« on: April 02, 2019, 12:35:33 PM »

Hello,

I have recently spent a lot of time trying to understand the way the interior camera calibration works in Photoscan.
I export the cameras to an Inpho.prj file and I noticed that the values displayed under "Tools"->"Camera Calibration..." (both the adjusted and initial values) vary greatly from the ones shown in the Inpho.prj file.
And I noticed that no matter what values are displayed for cx and cy under "Camera Calibration...", the "$PRINCIPAL_POINT_PPA" parameter in the inpho file is always zero. I tried manually inserting values with the "precalibrated" option and the "fix calibration" option checked but the principal point in the inpho file was still at zero.

Is it in the nature of the Inpho.prj format to ignore the principal point or am I making a mistake?

Any help will be much appreciated!