About this project

Online geographic tools allow historic maps to be overlaid on modern mapping, enhancing the ability to view and compare the past with the present, and improving findability. Georeferencing, i.e. assigning points on a map image to corresponding geographical co-ordinates, links the map to its spatial location on the ground using universal geographic standards (latitude / longitude).

Background

The British Library began a project to crowdsource the georeferencing of its scanned historic mapping by partnering with Klokan Technologies to customise its online Georeferencer product. The initial pilot, launched in February 2012, was a tremendous success, with all 724 maps georeferenced by the public in less than one week. The success was repeated with the second and third batches of maps in November 2012 and January 2013.

The maps

Each release of maps in BL Georeferencerhas been distinct, and together the over 2400 maps in the project (thus far) represent the variety of materials held at the British Library. The range of mapping, including diverse places, dates, mapmakers, purposes and scales, can also be considered a sampling of our cartographic heritage.

The content included in the most recent and most successful lot of mapping was specifically non-UK places, and all were maps that had not been seen online before. The initial round of BL Georeferencer was limited to two well-known British map collections, The Ordnance Surveyors' Drawings and the Crace Collection of maps of London, and the second round continued the latter along with the addition of maps from King George III’s Topographical Collection and selected 16th and 17th century manuscript maps of British places. The latest worldwide collection was selected by British Library readers, and for the most part reflects British interests and activities abroad. Maps of Asia and Africa are freqently of areas of special European interest during the 19th and 20th centuries; maps of European places feature topographic and military maps heavily; and maps of the Americas hint at the history of British activity in the New World

Results

Through georeferencing, maps are spatially enabled, making them geographically searchable and able to be visualised using geospatial tools and combined with other maps online. In less than two weeks after the initial work was completed, the first set of maps were added to the portal Old Maps Online, which uses a geographic search interface to identify and view historic maps from numerous collections online. All future georeferenced maps will also be made available via the Old Maps Online portal.

The output of this work may also be viewed using the BL Georeferencer interactive map, or browsed and searched from the Online Gallery map pages. Users are encouraged to add points to maps to improve the georeferencing, and to use the "Clip" tool to mark the borders of the map so that margins may be removed to improve viewing and allow seaming of contiguous maps.

The Library is grateful to all the participants who generously contributed their time, in particular to a the small groups of "expert" users whose commitment has been notable.

Further information

Queries should be directed to georeferencer@bl.uk. To connect with other users of this technology and participate in discussions, join the User Group of our technology supplier, Klokan Technologies.

For more information on the initial implementation of the British Library Georeferencer, see Kimberly C. Kowal and Petr Pridal. "Online georeferencing for libraries: the British Library implementation of Georeferencer for spatial metadata enhancement and public engagement" Journal of Map & Geography Libraries: Advances in Geospatial Information, Collections & Archives, 8:3, 276-289. To request access to this article online, contact georeferencer@bl.uk.