The Radar (also a Satnav in GTA IV), is a map on the Heads-up Display showing the player's current location in the game, and the relative location or direction of various points of interest. Introduced in Grand Theft Auto III, the radar essentially replaces the player centered location compass used in preceding GTA games, and remains an element of all GTA games after.
Blips on the radar show the location of various points of interest such as:
Mission targets - Initially indicated only by colored squares in GTA III, radars from GTA Vice City onwards specifically use squares for targets on the same physical level (altitude) as the player, and a triangle pointed upwards if the target is above or a downwards triangle if it is below. In GTA IV, the radar uses coloured circles; if the target is higher or lower, there will be a small arrow inside the circle.