African maps are notoriously problematic. Much of the data is old; roads, particularly footpaths, languish unnamed. Africans often navigate by informal landmarks like bars or gas stations, places not represented on standard maps. The slums have it even worse: On Google Maps they figure as blank expanses, in keeping with their reputation as shadowy, marginal places.

Enter Spatial Collective and Map Kibera. These two organizations, a company and a nonprofit, are mapping a Kenyan mega-slum called Kibera—the name is derived from a word meaning “jungle”—according to how its 200,000 inhabitants actually navigate it. The maps started with crowdsourced landmarks important to locals: water taps, schools, pharmacies. Residents with Internet access were invited to add to an open source map; others contributed data by SMS or attended community workshops, where they wrote on giant empty maps.

Spatial Collective overlays these community-generated maps with official data. One project tacked on sewer-line data (depicted here) from Nairobi City Water to find the most valuable spots to build new public toilets. Another mapped community-reported crime data to help the World Bank understand where to place safety interventions like lamps. These kinds of projects make Kibera more legible to its inhabitants and to outsiders.

By Eve Fairbanks John Grimwade