I assume you mean "Astrometrics".
In ENT, the Astrometrics lab was the ship's location where Stallar Cartography was performed. I would assume, however, that Stallar Cartography is just one aspect of Astrometrics.
Stellar Cartography is simply mapping. It is far more complex, of course, than mapping the surface of a planet, as all bodies are in motion relative to one another, you're mapping a 3-dimensional space, and the vast distances involved mean being throrough and complete is extremely difficult. In the end, however, it is simply creating a visual reference for locations in interstellar space.
Astrometrics as a whole, on the other hand, likely involves heavy statistical analysis in order to sort of "predict" what we'll encounter next.
A very simple example might be that if we're attempting to chart unexplored inhabitable planets, and we come across a star that tends to give off degrees of radition that make habitation of its solar system impossible, we'd likely decline to chart that system specifically because the odds of it having a habital planet are low.
Astrometrics is (likely, my interpretation of course) the mathematical approach to the study of space. The main difference between what we usually see is that, typically, science deals in what is, and the only place for speculation is to form a testable hypothosis. Astrometrics, on the other hand, deals in probabilities and odds, and specifically attempts to fill in gaps in knowledge based on those probabilities so that a given starship can make the most efficient use of it's time.
I am a software designer. To us, "Metrics" are statistical measurements of consumer behavior. How many consumers use Feature A as opposed to Feature B, etc.. It's used to sort of "predict" what features in a software product the consumer is most greatly in need of, what features need refinement, etc..
