Toward the end of Blade Runner 2049, Officer K decides to attempt to rescue Deckard from Wallace's control. Deckard is being transported to the airport on Wallace's behalf by Luv when K intercepts them.
How did K know where to find Deckard?
Earlier in the film, at least two other locating strategies are revealed. I think neither would be relevant to K at this time in the story:
First, Luv is able to locate K, when he is in Las Vegas looking for Deckard, using Lt. Joshi's computer. But access to this system is restricted (Luv uses Joshi's face to unlock it). K is a rogue Blade Runner and told by Joshi that he will have 48 hours before he is hunted. I think it's safe to imply that a rogue Blade Runner would have access revoked to restricted systems. Additionally, if the system could be used to find Deckard, I think Luv or Wallace would have used it to find Deckard directly. They already knew he existed and were looking for him (as were others). This didn't happen during the film timeline, or before it, so I think the system on Joshi's computer can't locate Deckard.
Second, Marietta and the replicant rebels are able to locate K using a tracker planted on K earlier. We never see K plant a similar tracker device on Deckard, so I think he shouldn't be able to track him this way.