The Spice Islands' urban planning director, Dr Muhammad Juma, is a pioneer in mapping technology, using drones to get a clear picture of Zanzibar's urban sprawl. But it was an innovation borne out of necessity - the archipelago's population is booming, and so are its slums.

Katie Prescott travels to the Tanzanian province to meet the man. She also speaks to drone pilot Khadija Abdulla Ali, one of hundreds of young people involved in the mapping project, and - unusually in this traditional Muslim country - a woman in charge of a team of men. Plus Sebastian Dietzold, who is building an entire new eco-friendly conurbation called Fumba Town.

(Picture: Dr Muhammad Juma, director of Zanzibar Urban and Rural Planning; Credit: Chris Morgan/BBC)