These pages of essays, notes, tabulated data and analysis (equivalent to a medium-sized monograph) cover a wide range of issues relating to the portolan charts of the Mediterranean and Black Seas, with the adjacent Atlantic coasts. They do not, however, attempt to offer new insights into the charts' origin or the methods employed in their mathematical construction.

Instead the concentration is on the charts' development and the reasons for their continuation, broadly unchanged over four centuries. This does not necessarily, or indeed usually, mean progress but rather the introduction, perpetuation or alteration of personal or regional stylistic 'signatures', against a broadly unchanging backdrop. The main dynamism, and one not immediately visible, relates to the charts' toponymy. A detailed study of the 1,800 names around the Mediterranean and Black Sea coasts reinforces some earlier conclusions while confounding others.

Some surprising findings have resulted from various detailed analyses of virtually all such works produced up to 1469, and selectively of those created thereafter - insights that were not possible on the basis of earlier partial studies.