DRADIS
DRADIS (Direction, RAnge, and DIStance) is a detection, identification and tracking system, somewhat similar to radar, used aboard colonial warships. Much like real world radar, there are also stationary DRADIS stations. The Cylons were able to jury-rig the DRADIS assembly from a Heavy Raider into a stationary DRADIS tracking array. ("Fragged")
This is an unfortunate acronym, since "range" and "distance" are redundant with each other.
Carbon composites are largely invisible to DRADIS scans (Flight of the Phoenix).
DRADIS is likely a central component of the Navigation computer on Galactica.
Notes
The "Direction, RAnge, and DIStance" breakdown of the acronym "DRADIS" was listed in an early manuscript (PDF) of the first half of the Mini-Series. Since some major elements of this script were changed (such as Kobol being the sole home of the Colonies, and not separate worlds) in comparison to the completed teleplay, canonical use of this breakdown should be taken with some skepticism.
However, there still is some evidence to suggest that the original breakdown is the canon version. In "Kobol's Last Gleaming Pt. 1" Crashdown performs a DRADIS sweep of Kobol. That aerial survey is then presented to the President. For a brief moment as she is just taking the survey image out of Billy's hand you can see the DRADIS information printed on the image. The letters on the image are clear and are as follows:
Aerial Survey D. 41376 Ra. 145.8 Dis. 43.5
The numbers may not be accurate or complete as we cannot see much further to the right of the image. However, given that the letters do represent numerical values, most fan-suggested alternatives for the breakdown of DRADIS would seem to be unlikely. While this is not conclusive evidence, it is consistent with the orignal manuscript definition.