I understand that the minimum number of GCPs needed for georeferencing (if using GCPs) is three and each of those GCPs must reference at least three corresponding image-tiles.
For example:
+proj=utm +zone=19 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
679085.942943119 3719568.30453006 45 2840 2270 DSC07327.JPG
679085.942943119 3719568.30453006 45 3270 4240 DSC07330.JPG
679085.942943119 3719568.30453006 45 3267 4233 DSC07399.JPG
679173.745053368 3719679.57853239 45 5770 1810 DSC07800.JPG
679173.745053368 3719679.57853239 45 5720 1770 DSC07801.JPG
679173.745053368 3719679.57853239 45 5710 1760 DSC07803.JPG
679173.745053368 3719679.57853239 45 5740 1780 DSC07802.JPG
678909.983778542 3719706.77584695 45 3240 1620 DSC07369.JPG
678909.983778542 3719706.77584695 45 3244 9040 DSC07366.JPG
678909.983778542 3719706.77584695 45 3222 9330 DSC07766.JPG
What happens if you reference a fourth or fifth GCP, but in less than three images like so?:
+proj=utm +zone=19 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
679085.942943119 3719568.30453006 45 2840 2270 DSC07327.JPG
679085.942943119 3719568.30453006 45 3270 4240 DSC07330.JPG
679085.942943119 3719568.30453006 45 3267 4233 DSC07399.JPG
679173.745053368 3719679.57853239 45 5770 1810 DSC07800.JPG
679173.745053368 3719679.57853239 45 5720 1770 DSC07801.JPG
679173.745053368 3719679.57853239 45 5710 1760 DSC07803.JPG
679173.745053368 3719679.57853239 45 5740 1780 DSC07802.JPG
678909.983778542 3719706.77584695 45 3240 1620 DSC07369.JPG
678909.983778542 3719706.77584695 45 3244 9040 DSC07366.JPG
678909.983778542 3719706.77584695 45 3222 9330 DSC07766.JPG
679173.745053368 3719679.57853239 45 5850 4250 DSC07797.JPG
678997.654453108 3719818.15670403 45 6510 1730 DSC07756.JPG
678997.654453108 3719818.15670403 45 5810 1840 DSC07757.JPG
Are those ignored or do they nullify the entire gcp_list.txt file?