Documents in Medieval Latin states that (page 18)
Large numbers of maps, from small areas such as the English counties to world maps, were published from the early 16th century onwards. Many contain descriptions of considerable length in Latin, often in good literary style (they were, of course, published documents, aimed at the educated and wealthy).
I understand that Medieval Latin and New Latin were in use during the early part of this period, especially for scholarly applications, but it seems odd that maps would be annotated in Latin. If made for practical use, surely they would be made in the common native tongue of the user(s), so those not fluent in Latin could understand it.
So why were many maps annotated in Latin - or am I making a false assumption somewhere?