How do you know where Latios/Latias are at in Ruby/Sapphire?

Question

Because on Bulbapedia, it says that you can see its location on the Pokedex as long as you have seen it, but I haven't seen Latios or Latias.

Answer 1

In your case there is no way to know, you will have to be patient and encounter it before you can know where it is. Note that whenever you enter a building, exit a building, use fly, or change routes it flees to a new route. Just hope you encounter it

Answer 2

These is a way to know where it is in Ruby/Sapphire.Just look at the pokedex.But,
B3N is also correct because you won't be able to track it in your pokedex untill
you see it.

Source:Personal Expierence