Problem in using gcp file

Hi All.
I have a problem using gcp in my dataset. I started a project years ago, making reconstruction with images that does not have any exif data. I was using gcp file to improve the quality of reconstruction. Recently, i updated OpenSfM, and when i make test with or without gcp file, i get the same result. I am wondering if i am making a mistake, or if i made a mistake in my previous tests.
My questions are : with the current version of OpenSfM,

• If images contain no GPS data, that is, no longitude, latitude or location data of any kind, is GCP required for reconstruction ?
• If GCP is not required, how is the reconstruction algorithm doing alignment between images in the images set without location metadata or GCP ?
• What configuration options, if any, must be changed to support metadata based alignment (No GCP), GCP alignment, and NAIEVE alignment (NO metadata and no GCP) ?

Thank you for you answer, for helping me to understand what is happening.

Issue #347 names no files, tests, or entry points. Start by comparing the reported OpenSfM reconstructions with and without GCP, then inspect the current configuration and alignment documentation; done means explaining whether GCP is required without location metadata and which settings apply to metadata, GCP, and naive alignment.