What is a geographic coordinate system used for?

A geographic coordinate system is primarily used to define a location on the Earth's surface using a system of latitude and longitude. This system provides a way to represent any point on the planet with specific coordinates, making it invaluable in cartography, navigation, and GIS applications. Latitude indicates how far north or south a point is from the equator, while longitude measures how far east or west it is from the Prime Meridian.

In contrast, defining distances on a flat map is not the focus of a geographic coordinate system. While one could measure distances on a flat projection, this does not inherently relate to how coordinates are defined. Similarly, calculating surface area and creating 3D models pertain to different aspects of spatial analysis and modeling that are typically conducted within GIS but do not stem directly from the geographic coordinate system. Thus, option B correctly identifies the primary purpose of a geographic coordinate system as facilitating the identification of specific locations on the Earth using a globally recognized standard format.