Like djinn posted read it carefully.
And artillery issent just spot, zero the dials and fire.
It is how fast you can adjust your fire to the target, Remeber what the battle looks like
What is very important, is where you're artillery lands.
If you have the choise, between a flag far from the frontlines, where people wait for a tank or so(easy kills) or a flag what you'r team is gonna assault and soften it up for them
You do the second thing.
Coordinate artillery> Landing shells on spawnzones behind enemy lines