A detection grid deployed in an unnamed star system
A detection grid was a type of sensor grid or sensor net.
The Torothan overlords of a planet used an orbital detection grid which in fact turned out to contain a gap. (ENT: "Desert Crossing")
During the 22nd century, the Xindi used a detection grid as a method of detecting the presence of starships in the Azati Prime system. (ENT: "Azati Prime")
Another type of detection grid was used at Imperial Hall in the 24th century on Ilari. (VOY: "Warlord")
The Federation and Klingon Empire both employed sophisticated tachyon detection grids as a means of detecting cloaked ships. (TNG: "Redemption II", "Face Of The Enemy"; DS9: "Apocalypse Rising")