The radar's role is to show to the player his immediate surroundings as well as waypoints and points of interest.
In Watch Dogs, as well as in many open world games, the radar shows a portion of the map like a GPS does, with a cursor indicating the position of the player, and the direction they are facing in relation to North.
The Watch Dogs radar features, in addition to all mission related waypoints, all points of interests, such as subway stations as well as hackable items such as traffic lights, lift bridges, and traffic cameras. To avoid the radar looking too "overcrowded" with icons, hackable items are only shown depending on what the profiler is set on. For instance, if set on Bridge Control, the radar only displays the location of lift bridges.
The radar scale will vary according to the vehicle that the player is driving and the distance of hostile enemies (if there are any), meaning that the radar will always be displaying the most suitable scale.