Screenshot of map Georeferencer

Do you like old maps and historic places? If so, why not give our Georeferencer tool a try? It lets you place historic maps over the latest maps so you can compare the past with the present. Your contribution to this project will help the British Library make its maps fully searchable and viewable.

Published date:

Before you start georeferencing, you may like to find out how to use the Georeferencer.

Join the latest phase of our project, which features over 50,000 maps from the British Library collections. Help us identify accurate locations for these historic maps! Bear in mind that some places have changed significantly or disappeared completely, creating an exciting puzzle that requires detective work.

Georeferencing involves assigning points on a map image to corresponding geographical coordinates. It links the map to its spatial location on the ground using universal geographic standards (latitude / longitude).

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 19th century, described here.


The British Library began a project to crowdsource the georeferencing of its scanned historic mapping in 2011 by partnering with Klokan Technologies to customise its online georeferencing tool. There have been five public releases of maps since 2012, all of which met with tremendous success. In total over 56,000 maps have been “placed” by participants, many of which have been reviewed for accuracy.

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 selection 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 well-rounded 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.


Georeferencing adds location data to map images, making them geographically searchable and offering the potential for visualisation and analysis using geospatial tools. All georeferenced maps are added to the portal Old Maps Online, which provides a geographic search interface to historic maps from numerous collections online.

The output of this work may also be viewed using the BL Georeferencer interactive map below or 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

For articles on the the British Library Georeferencer and georeferencing in libraries see:



The British Library collection of maps, plans and views is one of the largest in the world, numbering some 4.5 million