A basic solution to describing location is the use of a coordinate system. Planar coordinate systems provide a means for describing any point, line or polygon in a consistent manner, providing all the benefits of traditional analytical geometry, leveraging the power of several branches of mathematics. A Cartesian coordinate system is not appropriate for a sphere, however. A line connecting two points on a sphere is not straight, but rather bends around the curved surface of the sphere over three-dimensional space; there are no parallel lines on the surface of a sphere. The conventional way to report geographic coordinates is to first list the latitude and then the longitude. Many mapping applications, such as navigation, surveying, and military operations, require describing locations with high accuracy. Geographic datums essentially serve the same role as the axes in a planar Cartesian coordinate grid, as references against which the coordinates are specified, giving them meaning.