The tattooed coordinates
How did the resistance know that Grace would find help (from a rogue T-800 who became human friendly, thank you very much) in 2019 at these coordinates?
I can only theorize that maybe Carl survived until then and was helping the resistance? We absolutely have no clue of this in the flash-forwards though.
Maybe it was mentioned in the movie and I missed it or maybe there's a simpler explanation that I'm not seeing.