As concepts they are real, but as physical, tangible things they are not.<quoted text> But despite their concepts, they are used to determine real things. So, by that, they are real.
Iceland for instance is an island and as such surrounded on all side by water. Disregarding wave and tidal action, you can see where the land and the sea meet. It is a boundary established by nature on physical principles and we can see it. Longitude, latitude, and political borders are not physically real, but the concepts they represent are real. I think in the sense of concepts you see them as real, but in the sense of an actual line somewhere, they are not. These were all established by people and don't represent some natural line that we somehow found or tuned in on. We could just as easily pick a different set of lines and use those.
Don't forget, a map is just a metaphor and metaphors are never perfect.