Teleport takes you to a designated location, not a relative position - you can't teleport to "Latitude 52 Longitude 18" without knowing what is there. Dimension door does allow you to teleport to a relative position (e.g. "82 feet north and 27 feet west"), but it has a very limited range.
Is there a way to teleport to an arbitrary location without being familiar with it? So that, for instance, you could tell your wizard friend "meet me at [coords]", and they would be able to do so without having to scry it first?
Note that a coordinate system is not the point! The point is that a wizard who has visited town A and B can teleport directly to them, but he can't teleport to midway between them. He can see them on a map, and he knows roughly how far apart they are, and can teleport from one to the other - but not from one to halfway to the other.
The teleport spell requires a visual description of a location. You can't teleport to "5 miles that way" or "the other side of that hill" or "halfway between A and B" or "30 miles due north of Neverwinter". Not unless you've already seen it, or someone who has can describe it to you. I'm asking if there is an alternative method of teleporting, which would allow you to specify the location by some means other than picturing it visually.