Deck Zero is the center deck of Pathfinder starships. Deck Zero is the location of the ship’s pseudo-gravity grid, which creates artificial gravity within its area of influence.
Deck Zero is critical to both maintaining a sense of weightfulness for the crew of these ships, as well as being integral to channeling gravimetric forces generated by the ship’s propulsion systems into a systolic drive field.
Decks above Deck Zero are numbered positively. (Deck +1 through Deck +100.) Decks below Deck Zero are numbered negatively. (Deck -1 through Deck -121.) Because of the gravitational orientation, persons walking on a negatively numbered deck seem upside relative to a person on a positively numbered deck, and vice-versa.
On most Explorer, Defender, and Supply ships and all Fast Attack Corvette Series Ships, Deck Zero forms the main keel of the vessel, so that all decks are numbered positively.