Discovering Old Maps Online and Transforming Them Into Digital Humanities Resources

Hundreds of thousands of historical maps have now been scanned and made available on-line by libraries and archives around the world, and this has been a great boon to anyone interested in the history of cartography. Despite this fact it is hard to find scanned maps covering area of interest in the large number of online catalogs, library systems and web presentations on the web. The traditional full text search engines, such as Google, are failing to index the scanned maps properly.

Old Maps Online (www.oldmapsonline.org) is a search system tailored just for historical maps. Pick a location on a world map, or type in a place-name, narrow the search by selecting a date range. A listing of all possible maps covering that location appears, ordered by best geographical match. Select a map, click on the link and you go directly to view the map on the original library’s website.

You don’t need to know who holds the map, just when and where in the world you want to look at. This system is designed to complement rather than compete with libraries' own search interfaces. The system is powered by the enhanced version of the MapRank Search technology and indexes over 130.000 scanned high-resolution maps already and this number grows.

Many major collections in the US, UK and elsewhere have agreed to contribute: The British Library, Harvard Library, National Library of Scotland, David Rumsey Map Collection, Dutch National Archives, Moravian Library, New York Public Library, Norman B. Leventhal Map Center at the Boston Public Library, National Library of Australia, etc. Cooperation with the Europeana project has started as well. Our aim is to include as many collections as possible, so map libraries and collectors are encouraged to participate.

To be able to index the scanned maps geographically, the minimal metadata (title, creator/publisher, date, identifier, and a stable url) plus geographic coordinates for the area covered must be known for each map.

We develop and maintain set of online tools targetting librarians, scholars and volunteers allowing to create the coordinates and assign precise location to the existing online zoomable maps. One of the tools is the Georeferencer online service, which allows rapid collaborative georeferencing, 3D visualization, annotation and accuracy analysis of scanned online maps directly in a web browser environment, without the need to install any additional software on a local computer. The online visitors can help with the metadata enrichment and georeferencing of the scanned maps - and they are motivated with competitions, rewarding, community participation and recognition during this crowdsourcing effort.

With the presented online tools the enrichment and reuse of scanned maps is very straightforward. Recently the system has been improved and extended also with the functionality for favouriting the maps, for creating custom virtual map collections and for overlaying and comparing of the old maps. New tools for annotating and for exporting produced geodata or reusing the maps in a form of the standardized online services OGC WMS / OGC WMTS are integrated as well.

The Georeferencer service is applied in several institutions such as the British Library (London), the David Rumsey Map Collection (USA), the Moravian Library (Brno), the Nationaal Archief (The Hague), the National Library of Scotland (Edinburgh), and the Institut Cartografic de Catalunya (Barcelona).

Next to the service for discovery and indexing of these beautiful valuable resources, and next to the mentioned online tools for collaborative metadata enrichment of the scanned maps, this paper shows also practical applications of free and open-source software projects for online publishing and presentation of high resolution maps and vast collections of large raster images in general. Thanks to the modern web technologies such as HTML5 and WebGL it is now technically possible to bring the maps into web mashups and custom online applications directly.

The maps are undoubtedly extremely important documents for scholars, experts as well as interested general public. Once enriched with the precise geolocation and additional annotations, they are turned into a vary practical reusable online resource. Applying presented available tools and methods in a large scale opens opportunities for completely new forms of research in the area of digital humanities, which has never been possible before.