Above: Portolan chart of the North-West coast of Europe, including all of France, the British Isles and Ireland, Grazioso Benincasa [1473, Egerton MS 2855, f.8r]. File at Wiki Commons.
Over the past few years the British Library has been working with the Pelagios project, making innovative use of historic manuscript maps. Meaning ‘of the sea’ the name Pelagios is used as the seas were the highways of the ancient world, much like the Web provides a highway for communication today. A web-based project that facilitates the online linking of data about ancients sites mentioned, for example, in texts, local histories or where archaeological remains have been found. The current phase of Pelagios (in which the Library was involved) will soon be drawing to a close as the next phase, 'Pelagios Commons', begins and runs to December 2017. The Library has contributed digitised materials to phase 3 of this project, predominantly in the form of mappae mundi, itineraries and portolan charts, and these have been digitally annotated to open up the enclosed geographical information to the Pelagios database.
Above: A map of England, Northern France, Scotland and Wales from Insularium Illustratum, Henricus Martellus Germanus [1495, Additional MS 15760, f.53v]. File at Wiki Commons.
As you can see, the material provided to Pelagios is something of a treasure trove of manuscript views of the world and the project as a whole is composed of various wonderful resources detailed at Pelagios Commons. Now that our involvement with phase 3 of the Pelagios project is drawing to a close the Library is making the material it contributed to the project available on Wikimedia Commons and (soon) via data.bl.uk. The main root for material held on Commons can be found on the British Library Map Collections category page on Wikimedia Commons, which provides links to the various groups of British Library manuscript materials used in the Pelagios project (although I should note this is a general collections page - so you will not find Ordnance Survey Drawings in Pelagios!).
Above: General chart of the coasts of Europe, the Black Sea, the Mediterranean, and the western coast of Africa, Cornaro Atlas [1492, Egerton MS 73, f.36r]. File at Wiki Commons.
One health warning about these manuscripts, due to UK copyright law they are technically in copyright until 2039. However, given the age of the manuscripts and their place of production the Library believes it highly unlikely a public domain release will offend anyone; more information can be found here. Copyright notices aside, this is a fantastic resource which we hope you enjoy. If you do dive make sure you clear your diary and sit down with some food to see you through, it's a fascinating collection of material. If you want to know more about Pelagios generally - and perhaps join in - head over to their Commons site. Here you can access online resources that are being developed (using open data methods) to link and explore historical place, as well as participate in various community forums. You can also find more at the Digital Classicist Wiki.