"That the Science of Cartography is Limited" is a pretty striking title. It acts as a hypothesis that the poem will go on to prove. (And prove it, it does.) By the end of the poem, we are thoroughly convinced that map-making has its limitations, that maps can never fully capture the cultural or historical context of the Irish landscape… not to mention our human selves' experiences, which are all wrapped up in that land.
If you're digging the strangeness of the title, we've got a whole lot more for you to think about. Head on over to the "Summary" section on this poem; there's some hardcore title analysis there for you to chew on.