For the past six months, 1,650 Humanitarian OpenStreetMap Team (HOT) volunteers from more than 100 countries have worked around the clock to produce detailed maps of areas affected by West Africa’s Ebola outbreak and get them into the hands of humanitarians.

Volunteers in Togo contributing to #map4ebola with help from Espace OpenStreetMap Francophone (EOF). Photo courtesy of EOF.

West Africa is now HOT’s biggest-ever project, and the results are incredible. HOT volunteers have added more than 9 million objects to OpenStreetMap’s coverage of Sierra Leone, Liberia, and Guinea since March 2014, including 29,000 place names, 123,000 km of roads, and 774,000 buildings.

Here’s a visualization of all that mapping work:

HOT’s building data makes house-by-house contact tracing easier. And HOT’s detailed road and infrastructure maps help governments and aid organizations move supplies and patients efficiently.

If you want to help, HOT will walk you through the process. If you’re already familiar with OpenStreetMap editing, check out HOT’s task manager to see areas in urgent need of mapping.