Cartography

The poem's title is a proposition: that the science of cartography (also known as map-making) is limited. Maps can't represent everything, the title proposes, and the rest of the poem acts as a proof of this idea. So, maps may be useful in telling us the best way to get from Dublin to Galway, but that doesn't mean they represent all of the landscape accurately.

• Title: The poem begins with a hypothesis: maps can only represent so much. By the end of the poem, the speaker has definitely proved this hypothesis to be true. In yo' face, you navigators with your mappy maps.
• Lines 1-4: The speaker begins by listing some things that maps can't capture, including the smell of the woods and the gloominess of cypress trees. 
• Lines 19-24: The speaker enumerates all of the things that maps are awesome at doing: rendering a round earth on a flat plane. Which we have to admit, is kinda cool.
• Lines 25-28: What motivates this list of things that maps can do is to explain what they cannot do. The speaker recognizes that maps do not represent the nation's famine roads. So, maps don't show history, politics, or tragedy—they only represent what's "useful" in the present. But we think it's pretty useful to remember what's happened, lest we want to repeat the past.