Such maps can offer infrastructure and emergency planners a quicker solution to know more updated data on population density and mobility than even what traditional census data provides. Every time a person uses a mobile it sends information to a receiving tower and gives an approximate location of where they are.

"When this information is repeated multiple times, over millions of users, we can extract a detailed picture of population density and how it changes over time in a given area," said senior study author Andy Tatem from University of Southampton in Britain.

The researchers used the anonymised mobile phone records of 19 million users in Portugal and France, for several months in 2007 and 2008, to generate maps showing the densities of users in different geographic areas.

The researchers found that using mobile phone records to map populations has many advantages over traditional census information."Anonymous phone data can be examined regularly to map daily, weekly or monthly changes across an entire country, at less cost and with greater flexibility," Tatem explained.

At the moment mapping of populations is constrained by the logistics of census surveys, which just provide a single snapshot of population distributions every ten years, Tatem pointed out. The results were reported in the journal Proceedings of the National Academy of Sciences.