The GPS (Global Positioning System) is a global navigation system that uses satellites in space around Earth that can calculate position and weather anywhere on the planet reliably, so long as at least four satellites have an unobstructed view to a receiver. It is maintained by the United States Government, but is freely accessible to anyone in the world.
The GPS system was created primarily for the US Military as a navigation tool, and its origins date back to the 1960s when the United States Navy used a total of five satellites to get a navigational position every hour. Today, the system is used for everything from reconnaissance to locating objectives.
Battlefield 2: Modern Combat
The player can activate the GPS with the fire button and any enemies nearby will be marked with an icon above their heads and on the minimap for a few seconds, marking their position. This feature can be used to great extent in Headshot if the player loses track of nearby enemies on rooftops or the ground, as some will try to move on the nearby allied Snipers if they are not taken out.
The GPS can be used to a similar effect as in singleplayer. It can be used to locate defenders of control points or in conjunction with the Sniper's AN-M8 Smoke Grenades to see enemies on the other side.