Torsten Sattler

1. All points will have a slight error as you have errors in your 2D feature detections. The more 2D-3D matches you have, the larger will be your sum of...

The alternative sounds a bit like the work by Heinly et al. You can follow-up on the research by Heinly et al. and the pointers provided in the first repository.

Have you looked at https://colmap.github.io/faq.html#faq-dense-manual-source ? If you triangulate the scene from known poses, it might happen that some images end up with no visible 3D points (there can be...

Are you sure that the images for which you get the warning have camera poses in the reconstruction?

It was not clear to me that you created the images.txt and cameras.txt files yourself. I assumed you ran the mapper. Did you run the point_triangulator and do the images...

Did you check whether the problematic images have 3D points in the model and share matches with other images in the database?

What is a noisy image?

Does Colmap find enough features in that image and is it able to match these features against the other images?

You can look at the matches in the gui (under database management).

This only shows that there is no pose prior for the images. Select an image and click on "Overlapping images" to see information about the matches.