I could go all kinds of places with the OP but...Avanti, the word you're looking for is coordinates - any of a set of numbers used in specifying the location of a point on a line, on a surface, or in space.
We do have a coordinate system though not nearly as precise as directing artillery fire would require. It would need something on the range of saying sector 11,2 - kp 5-5-2 so the fire can be directed to within 50 yards. Then we would have to be able to zoom in on the map a lot more too.