Standing in a sliver of shade cast by a solar streetlamp, David Kwaje plugs statistics into his smartphone.
Hidden from the harsh midday sun, he can see downhill to a row of white warehouses where residents collect food rations and beyond to two large tanks that supply water to roadside taps, yellow jerry cans radiating in all directions.
All week Kwaje has been walking along dirt roads, plotting every business, church, school, clinic, water tap, and light source on a digital map. At each stop he marks the location and asks detailed questions: Does your school have running water? What hours is this store open? How many doctors does the clinic have? By the time he and a half dozen other mappers finish, they’ll have created an open-source guide to an area that’s more than twice the size of Paris.