Most parts of Africa's infrastructure are yet to be built. Where and how
these new buildings are constructed matters since today's decisions will
last for decades. Satellite imagery enables the construction of urban
form indicators to compare African cities' elongation, sprawl and
emptiness. We characterise urban morphology based on the distribution
and size of millions of buildings in African cities. Many cities are
elongated or sprawled, especially urban areas dominated by small
buildings or close to physical barriers or international borders.
However, as the population increases, distances grow and become
critical, so cities experience intense competition for space and better
use it. Larger cities tend to settle more efficiently. For each city, we
measure the mean inter-building distance, a proxy for energy consumption
related to urban mobility. Distances inside a city grow faster than the
square root of its population, resulting from the combined impact of a
sublinear growth in the number of buildings and a sublinear increase in
building size and urban form indicators. We show that when a city
doubles its population, it roughly triples the energy demand related to
commutes.
