You can help Nepal's rescue efforts by mapping. Here's how

International rescue teams and locals throughout Nepal are still searching for the missing following last Saturday’s 7.8 magnitude earthquake.

This would be a difficult process anywhere. In Nepal, the country’s mountainous landscape has made things more difficult still, but making it hard to access many affected areas. Rescue teams need open spaces to land helicopters, especially in spots like the trekking area to the north of Kathmandu, where 200 people are feared missing following a landslide Tuesday. In remote areas, routes into communities may be badly mapped, or not mapped at all.

This is where you come in. Yes, you. First, in donating if you can to the rescue efforts -–more on that here. But there’s also something you can do, for free, from your own computer (even if the fan’s dodgy and it crashes when you’ve got more than ten tabs open): make maps.

Don’t panic, this is much easier than it sounds. A site called OpenStreetMap allows volunteers to work from satellite imagery to create maps of previously uncharted territory on an open-source, global map. Using the tools on the site you can trace out buildings and mark out large open spaces where the terrain looks flat enough for a helicopter to land.

An organisation called the Humanitarian OpenStreetMap team (HOT) is encouraging people all over the world to contribute to the mapping of Nepal, and have put together a priority list of spots where rescue teams are in urgent need of better or updated maps. In turn, they’re processing new satellite imagery of the areas, so volunteers are working from the most up-to-date, post-earthquake photos.

To join in, you need to sign up to OpenStreetMap (which only takes 30 seconds or so), and go through a tutorial like this one. Then, click on one of the HOT priority areas on their site and follow the on-screen instructions on how to find and mark out open spaces, roads and buildings.