gcp photo tagging guidance

[itenviro]

I use gcp editor pro and am looking for more precise guidance on tagging the photos with gcps from someone with more knowledge of sfm than I have. The project has approximately 10 000 photos. Overlap is 85%. Flight altitude was 60m. At this altitude and overlap some gcps are visible in more than 30 photos.
Should the gcp be tagged in every photo where it is visible and if not, how to select which to tag? For example should I tag the gcp if it is towards the middle of the photo and discard those on the periphery?

Second question - I placed gcps at the bottom of the embankment and at the top of the embankment. What do I do about tagging photos with 2 gcps, both necessary for accurate reconstruction?

[pierotofy]

@itenviro

gcp be tagged in every photo where it is visible and if not, how to select which to tag?

No, but you should tag it in at least 3 pictures, 5 is better, more than 5 is probably not going to increase the accuracy much. Choose pictures that have good contrast / features / luminosity condition. You should actually do a mix of middle / periphery, it will help with camera calibration.

@itenviro

both necessary for accurate reconstruction?

Probably not necessary, but if you have them, tag them both? It shouldn’t hurt.

[itenviro]

Thanks very much. That’s all I need to know. Wasnt sure if too many photos/gcps would result in ambiguities in computation.