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About this project

The British Library’s Georeferencer project is crowdsourcing location data to make a selection of its vast collections of maps fully searchable and viewable using popular online geotechnologies.

Online geographic tools allow historic maps to be viewed alongside modern-day mapping, allowing comparison of the past with the present and enhancing findability. Georeferencing, i.e. assigning points on a map image to corresponding geographical coordinates, links the historic map to its spatial location on the ground using universal geographic standards (latitude / longitude).


The British Library began a project to crowdsource the georeferencing of its scanned historic mapping in 2011 by partnering with Klokan Technologies. This is the sixth release of maps since 2012; over 8,000 maps have already been "placed" by participants and subsequently checked for accuracy and approved for reviewers.

The maps

The latest release is the largest yet, with over 50,000 online map images. These maps were identified from amongst the illustrations extracted from books digitised by Microsoft and posted to Flickr Commons as Public Domain images. The task of identifying maps was entirely done by volunteers, via an online campaign with substantial support from Wikimedia UK. The tagging was initiated with a Maps Tag-a-Thon event at the British Library in November 2014, and continued online until completion in January. This latest collection therefore already represents a huge amount of public interaction and input.

The maps in this large release are all from books published in Europe, primarily from the nineteenth century, described here.

Previous releases of maps for georeferencing via BL Georeferencer included:

  • the Library’s collection of British and Irish first-edition Chas E Goad Co. fire insurance plans, completed in January 2014, which provides detailed information about buildings, land use and urban design at the at the turn of the twentieth century (1886-1930). This included over 2,500 plans covering 53 towns, cities and ports.
  • Two smaller map collections, one related to Britain and the American Civil War, and the other a selection of WWI maps
  • Earlier releases included a variety of maps dating from as early as the 16th century up to the twentieth century. Initially, two well-known British collections were released: The Ordnance Surveyors’ Drawings, the Crace Collection of maps of London, followed by selections from King George III’s Topographical Collection and a sampling of maps contained within 16th and 17th century manuscripts.
  • Maps of a modern vintage represented the themes of car, rail and air transport, along with topographic and military mapping. This has resulted in a better-rounded, if less orderly, representation of mapping of the UK and other regions of the world.

The history of the georeferencing project can be viewed from the British Library blog posts on BL Georeferencer.


Through georeferencing, the selected map images were spatially enabled, making them geographically searchable and able to be visualised using geospatial tools and combined with other maps online. All georeferenced maps are added to the portal Old Maps Online, which uses a geographic search interface to identify and view historic maps from numerous collections online.

The output of this work may also be viewed using the BL Georeferencer interactive map and directly from the Online Gallery map pages.

The Library is grateful to all the participants who generously contributed their time. Special thanks are extended to the expert panel of Reviewers, whose work to ensure the high quality of results was substantial. The appointed BL Georeferencer Reviewers are:

Chris Austin
Susan Major
Maurice Nicholson
Mark Setrem
Ian Pritchard
Kathryn Snow

Further information

Any queries about this project should be directed to To connect with other users of this technology and participate in discussions, join the User Group of our technology supplier, Klokan Technologies, at
For more information on the initial implementation of the British Library Georeferencer, see

  • KC Kowal and P 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. Online access.

For information about georeferencing in libraries in general, see

  • C Fleet, K. Kowal and P. Pridal “Georeferencer: crowdsourced georeferencing for map library collections”. D-Lib Magazine 18(11/12): 2012. doi:10.1045/november2012-fleet Online access.