Phantom 3 using reach

1.can Reach collect 2cm accuracy GCP by camera triggering events?
how to do this?
2.what modifications needs to be done to my phantom 3 pro?
3.what can affect accuracy, and what accuracy can i expect in final product?

my final product needs to be very accurate orthomosaic and contour lines. (probably using pix4d or similar).

hammer lior

  1. what is the maximum range between drone and land antenna?