Linking RDS Artemis ISOCAN to Greenstar for VRA

I have an ISOCAN Artemis controller for my new Claydon drill. I need to do variable rate applications of seed & flat rate fertiliser. How do I link this to the Greenstar for mapping, shape files etc? I have a wiring loom for doing this with my old Vaderstad Rapid. Do I need a null modem ro will a straight connection via the RS232 lead suffice?

I have a radar fitted to the drill but would a GPS signal be more accurate?

@towns