I think it might be better explained in Astronomical terms.
D = Direction as in compass degrees with the ships nose being 0 degrees (yaw)
RA = Right Ascension which is in degrees also with the horizon being 0 and directly overhead being 90 deg. and -90 for directly below (pitch)
DIS = Distance to target.
That would give you a 3 dimensional position reference
I would otherwise agree but in astronomy context Right Ascension means the target's
horizontal separation from a given reference point, and declination is its elevation from horizontal plane.
Reference point in astronomy is typically the point of vernal equinox; in three-dimensional coordinate system for a battlestar, you would probably use the direction of the bow as the fixed point of reference.
Right ascension in astronomy is typically given in hours, minutes and seconds (24 hours to full circle, 60 minutes to an hour, 60 seconds to a minute) because in the Equatorial coordinate-system, objects on celestial sphere seem to move due to Earth's rotation, and it made sense to bind their horizontal location with that horizontal movement; this was useful for porting the equatorial coordinates into local horizontal coordinates which are usually given in altitude (elevation from horizon) and azimuth (distance from north in degrees), both given in degrees.
Declination is given in degrees of angle above (or below) the equator.
The analogy of Equatorial coordinates vs Horizontal coordinates regarding the DRADIS is that if DRADIS used Declination, Right ascension and Distance, that means the navigational program would generate a reference coordinate system that would be the same for all ships, and movement in that system would be relative to this coordinate system. This would make some sense, as then the DRA coordinates of targets would remain constant even if your ship turned towards them or away from them; if all ships in your group used the same reference point, then you could use the same coordinate system to relay position information directly to other ships WITHOUT having them always convert the given values into their own local Horizontal coordinate system, in which the reference point would probably be the forward direction and the local "up" of the ship.
Perhaps the lead ship of a group of ships always transmits their initial reference frame to other ships' DRADIS systems and everyone uses this reference frame for the time they remain in the same system.
Note that ships in Ragtag Fleet always seem to perform jumps with same heading - perhaps this is to facilitate faster DRADIS synchronization, or something.
The "Direction, RAnge, and DIStance" breakdown of the acronym "DRADIS" was listed in an early manuscript of the first half of the Miniseries. 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.
There is some evidence to suggest that the original breakdown is the canonical version. In "Kobol's Last Gleaming, Part I", Crashdown performs a DRADIS sweep of Kobol. The aerial survey is later presented to the President. For a brief moment, as Roslin takes the survey image out of Billy Keikeya's hand, the DRADIS information printed on the image is visible. The letters on the image are clear and are as follows:
Aerial Survey
D. 41376
Ra. 145.8
Dis. 43.5
The letters represent numerical values. While this is not conclusive evidence, it is consistent with the original manuscript definition.
Well, the problem here is this:
Direction = 41376
Range = 145.8
Distance = 43.5
...sense, these values make none.
Even if you interpret the DRADIS acronym as Declination, Right Ascension, Distance, you get
Declination 41376
Right Ascension 145.8
Distance 43.5
...it still doesn't make perfect sense because 41376 doesn't fit in any angular units I ever heard of.
I would expect D (be it direction or declination) to be given in degrees. Right ascension in astronomy is typically given as degrees but can be easily converted to degrees, so the RA value in this example fits.
However, if you swap the D. and Dis. values, you get this:
Declination 43.5 (degrees)
Right Ascension 145.8 (degrees)
Distance 41376 (metres)
...which makes sense in that it gives two reference points for direction and one for range, which is what you can work with in a polar equatorial coordinate system.
Given this consideration, my most likely explanation for that "aerial survey" thing is that
they dun goofed.
Even if we considered that a goof-up, this still isn't any actual proof that this is what the DRADIS acronym would stand for. It would make some sense, but it isn't any sort of proof.
For all we know, DRADIS may not even be an official acronym but just something that sensor operators began using for reading out information readings, or for these two values always being shown in close proximity on the screen and being easy to pronounce together... and before you know it everyone starts to use the term.