Adrift : STARGATE ATLANTIS SEASON FOUR ....

ANALYSIS

A Stargate needs to remain in a relatively fixed location in space in order to be able to successfully dial out and connect to another gate. If a gate is located on board a ship -- including the city of Atlantis -- the city must more or less come to a stop (or at least not be moving too quickly) in order to dial out or receive an incoming wormhole.This is because the Stargate's dialing system uses relatively fixed points in space (denoted by star constellations) to identify a destination, as well as a symbol specific to the initiating gate's point of origin. If the gate is moving too quickly, at least its point of origin would be subject to change. (This is also why Stargate Command had to calculate for thousands of years of interstellar drift when correcting gate addresses from the original Abydos cartouche discovery ten years ago [SG-1: "Children of the Gods"].)This is consistent with the use of Stargates on board ships in past episodes, including Stargates placed on board Goa'uld motherships (SG-1: "Within the Serpent's Grasp," "The Serpent's Lair").