This map shows the average travel time to the nearest city from nearly every place on Earth. Daniel Weiss at the University of Oxford and his colleagues used data from the Open Street Map Project and Google to map the globe and determine how long it takes to reach an urban area based on distance and access to roads, waterways, and railways.

What they found:

In 2015, about 80.7% of people, or nearly 6 billion individuals, live within one hour of a city.

But 90.7% of people living in high-income countries can get to a city within an hour versus 50.9% in low-income countries.

Why it matters: Cities are hubs for jobs, hospitals and schools, and access to them can be a measure of opportunity. The new maps clearly show inequalities and a need for improving access. But it needs to be done sensibly, says Weiss. For example, clearing forest in the name of roads can lead to deforestation.

Why they did it: Maps like these are used by the World Health Organization to determine the burden of malaria (which Weiss studies and was the impetus for the current mapping effort), HIV, and poverty.

"You're left with tools to do interventions better," says Weiss. For example, it could help with planning roads and improving access to health care.

What's next: Weiss is working with Google to develop an online mapping tool that runs on the cloud. "We're trying to make something where a public health professional in Burundi can make their map without having the expertise [of a GIS professional] and computational infrastructure to do it," says Weiss.