The teleporter pad is also a stationary location relative to the ship that doesn’t move around. The teleporter probably has its coordinates hardcoded. A teleporter tech who isn’t as much of a wizard as O’Brien is probably relies on that pretty regularly.

O’Brien just happens to be capable of teleporting people to and from arbitrary locations because he’s a master of his craft. But if you get your calculus wrong in an emergency you’re going to teleport your captain and away team halfway through a bulkhead, or collect a thousand pounds of loose dirt alongside them and only half an ensign.