Enemy Detection is a passive Direction-Finding network for hostile ground activity. A station does not scan its whole network circle like radar, and even a level-3 station does not reveal an enemy's true position. A contact appears only when at least one sensor in the network receives that enemy type.

An active airfield can build and upgrade one Direction-Finding station in one of its two build sites, paid from the airfield's storage (see Airfields). The network radius decides which nearby active sites act as relay sensors; it is not the station's listening range. If a site lies inside several networks, it is assigned to the nearest covering station and uses that station's level and calibration.

Level 2 hears every enemy type, including everything a secure region still produces. Level 3 adds no new type; it pays in more relay sites, a wider network and much narrower cones. The station airfield hears further than a relay does, and a quiet emitter is heard less far than a loud one.

Detection is never guaranteed. Close to a sensor a contact is likely; towards the edge of its reach the chance falls away to nothing. A result holds for one detection period and is then evaluated again, so a stationary enemy can appear or disappear when a new period begins.

Every successful sensor produces a bearing cone without range information. Its width depends on the station:

• Level. A higher station level produces a markedly narrower cone.
• Calibration. A calibrated sector roughly halves the daylight error for bearings arriving from that direction.
• Darkness. Night widens every cone, and the lower the station level the more it suffers. Calibration cannot repair this part.

Distance also contributes to the A, B or C quality rating shown in the contact tooltip.

Fly any player aircraft 3-6 km from the station at 300-900 m above ground and remain continuously inside the same 30-degree sector for 20 seconds. Leaving the distance or altitude band, or crossing into another sector, resets the current dwell timer. Each of the twelve completed sectors is stored separately and improves bearings for every relay assigned to the station. Upgrading the station clears its calibration, because the antenna has changed. A sector keeps full quality for a long time and then fades slowly; the CAL layer shows what is still bright. The flight itself is described in Calibrate a DF Station.

With no received bearing, the enemy does not appear in the public threat layer. One bearing produces a single cone. Two or more bearings produce crossed cones, but players must judge their overlap themselves until the world has a Direction-Finding Control Centre.

The Control Centre requires three Direction-Finding stations at level 2 or higher. Once built, its global plotting service narrows every cone and automatically intersects two or more bearings. A wide intersection appears as a red plotted area, a tight one as a fixed point. That point is the calculated centre of the bearing intersection, not access to the enemy's hidden true coordinates.

The THREATS layer draws each unresolved bearing as a red cone made from five progressively fainter bands. Every cone is drawn at the same cosmetic length. Only its direction and opening angle carry information; the drawn length is neither an estimated enemy distance nor the sensor's detection range. A single bearing and unresolved crossed bearings have no contact marker, so their overlap must be judged visually. Once a contact becomes plotted or fixed, its dim cones are replaced by the red error area or point. The tooltip gives the enemy kind, resolution and the contributing A/B/C bearing qualities. Selecting a station airfield highlights all bearings reported through that station, including reports from its assigned relay sensors.

CAL shows the calibration band as twelve sectors around each station; a completed sector appears brighter according to its remaining quality.

• Calibrate a DF Station
• Respond to an Ambush
• Build a Project

• Ambushes
• Security
• Live Map
• Institutions
• A/N Direction Finding