Map of countries in Africa with background shading indicating approximate relative density of human populations (data from the Global Rural-Urban Mapping Project) Disclaimer: AAAS and EurekAlert!

Using maps obtained by satellite ocean monitoring, or from physical ocean models like the recently published one, researchers can more accurately predict whale density across the U.S. east coast.

Population density (often abbreviated PD) is a compound measure that tells us roughly how many people live in an area of known size. It is commonly used to compare how 'built-up' two areas are.