Matthew Edney poses an interesting question about measuring the physical size—i.e., the length and width—of paper maps: how do we do it, and why are we doing it? “There’s a philosophical question (how do we construe this thing that we need to measure?), the question of precision (how finely do we measure?), and a pragmatic question (what use is to be made of whatever measurements are recorded?), all of which influence the selection of which part(s) of an image are to be measured. Add to that a great deal of historical inconsistency in practice, and the question becomes difficult to answer.”