DRADIS ("Direction, RAnge, and DIStance") is a highly sensitive detection, identification, navigation and tracking system used to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, weapons ordinance, celestial bodies, and terrain.
DRADIS is a central component of the navigation computer, and defensive and offensive weapons systems, especially on Colonial warships that do not have windows or portholes of any kind that would allow an outside view of the vessel. Without it, the warship is blind. It is the first line of defense after enemy contact is made, alerting warship crews to any incoming danger, such as nuclear (which triggers the ship's Radiological Alarm) (TRS: "33", "The Captain's Hand") or conventional ordnance (TRS: "He That Believeth In Me"), and any objects that might pose a collision risk ("CBDR" - Closing Bearing, Decreasing Range) (TRS: "Pegasus").
Limitations and Interference
DRADIS systems are often subject to various sources of interference, and clutter. These can come from excessive contacts or naturally occurring objects such as nebulas, EM interference, star clusters, pulsars, and binary stars. There isn't much an operator can do to eliminate these sources, and must do the best they can given the circumstances. However, DRADIS systems can still eliminate these sources enough to detect objects at closer ranges (TRS: "Lay Down Your Burdens, Part II"). DRADIS operators can also "turn off" various sources of clutter, for example, excessive or uninteresting contacts can be toned down to simply an icon on the screen, allowing more important contacts, such as a ship's Combat Air Patrol, to be highlighted with its speed, direction, and transponder ID.
The Cylons also employ DRADIS on their spacecraft, however, in what capacity is not known. No visual representation of the Cylon DRADIS exists, as the corresponding tracking data appears to be uploaded directly into the consciousnesses of the Cylons in charge of command and control via the Baseship datastream (TRS: "The Ties That Bind").