How would they know?

???? How??? Even though Ed and Harriet are really acting creepy, I have to say, they are really good at navigating where Nancy, Bess, and Goerge are. But how?? How do they know? How do they know where they are?? Do they have a super sonic navigation system? If they do, is a micro chip attached to nancy? If there is a mico chip, how did they attach it???? On the train?