Detectors in Warhammer 40,000: Dawn of War III are basically units that are capable of revealing units with camouflage. Aside from some of the elite units that can use camouflage, there are three units in the entire game capable of "becoming invisible". Those are Scouts from the Space Marines, Rangers from Eldars and Orks' builders, Gretchin (after activating a special ability). Camouflaged units are invisible to enemies until they attack, or the enemy has a detector located near them.
The following units/buildings have the Detector trait:
- Space Marines builders, Servitors. Aside from the ability to use a special pulse that reveals hidden units, they have a passive ability granting them a revealing aura. Additionally, they can throw a mine. Once armed, the mine detonates as soon as an enemy unit appears near it, revealing it (it also works on normal units, revealing them on the map).
- Ork builders, Gretchin. Like the rest of the buildings they have a revealing aura and a special ability that allows them to launch a pulse revealing hidden units in the area.
- Eldar builders, Bonesingers. As with the Grechin, they can reveal units with a pulse and with an aura.
- Turrets and shields - both have a revealing aura.
Note - Detector abilities won't work on units hidden in bushes / stealth cover, unless the detector is located in the same bush / cover as the hidden unit.