Wiktionary
portolan
n. (context nautical English) A chart of European navigable waters based on descriptions of coasts. (from 18th c.)
Usage examples of "portolan".
There was no sign of the log and portolan charts, documents for which the Navy Office would have paid a handsome sum.
Some of these were the portolans used by merchant mariners in navigating, trading, living along the coasts.
True, I had read more of geography and studied more maps, charts, and portolans than most, and I had sailed what to Moslems were unknown seas, yet I was woefully ignorant of so much I needed to know.