I’ve been using GCP Editor Pro for GCP’s and was having GCP Error around 0.3m. It didn’t make sense to me since I was using good survey quality ground control. What I eventually discovered is that I had measured my GCP in UTM 14N NAD83 and should have converted my Lats/Longs to WGS84. I actually converted to WGS84 and then converted to UTM 14N coords and used the corresponding EPSG (32614) in GCP Editor. Error down to 0.011m.
Also, a quick tip for finding images with your GCP’s. I run a fast ortho and then turn the cameras on in the viewer. It’s a lot faster for me than browsing through 1000 images to find a small X.
It would be better if the Editor could help ID GCP images with the EXIF data but it’s not a huge inconvenience. I appreciate the work put into it as it works great!