DRADIS stands for "Direction, RAnge, and DIStance". It is the Colonial equivalent of radar and is the primary sensory system of Colonial vessels and also ground installations. DRADIS can be found almost everywhere from Vipers and Raptors to the CIC of a Battlestar. Some DRADISes are more powerful and more precise than others, but they all perform the same basic function to detect, identify, and track contacts.
DRADIS can also pick up more than just the direction, range, and distance of nearby contacts. DRADIS scans actively search for friendly IFFs, attempt to identify unknown signals and "guess" based on its qualities what the contact is, and even to detect radiological threats.