The EA detects two types of fratricide risks: (1) from calls for fire from other team members (which appear in messages from SAIM), and (2) friendly units near each other (which are detected from the geolocation data). In the first case, the user who issues a call for fire is warned and asked for confirmation if team members are within a given threshold of the target. If the request is confirmed, a SAIM message is sent to team members, and the EA of any entity within the target threshold immediately alerts its owner to the risk from the planned fire.
The second case produces far too many alerts if simple algorithms are used. Our algorithms are based on the Army's notion of unit boundaries, which are specified in the plan. When two units are within their boundaries, no alert is issued even if they are within weapons range of each other. Fratricide alerts are issued when one unit is in another unit's boundaries and within weapons range of the other unit. We handle numerous special cases, such as when two units are both outside their boundaries and within weapons range of each other. Detection of other fratricide situations is left for future work (e.g., misoriented units within their boundary).