Enthusiasts are being asked to update arguably the greatest map collection in the world. The British Library wants online volunteers to add further insights to its vault of ancient terrains, using Google Earth and location tagging to work out where historic sites might lie today.

The last time the library invited the public to help update its collection of more than 4.5 million maps, 708 new additions were made in a week.

“It’s easy to use and highly addictive,” explains Kimberly Kowal, the Lead Curator of Digital Mapping, who believes the global campaign will nurture the impressive digitised collections held in London.

“Although many locations have changed significantly over the centuries, sometimes almost beyond recognition, only a handful of common features – street intersections, buildings or some natural features – are necessary to link the past with the present.

“This project brings together people’s passion for maps and history with the latest online crowdsourcing tools.

“It’s a fascinating way to explore the past while improving the information that underpins our digitised collections.”

The Library’s third call for cartology fans is the first time the idea has gone global. Every continent is covered by the 800 maps singled out for inspection, ranging from the 17th to 20th centuries and put to purposes including military, topographic, ecological and planning surveys.

Contributors can plot locations, search for maps and navigate existing ones. The Library of Congress, in Washington DC, is the only venue in the world to hold a larger collection of maps.

• Visit bl.uk/maps to find out more. Maps from the previous projects can be seen at oldmapsonline.org.

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