Surveillance and collision avoidance system with compound symbols

A surveillance and collision avoidance system provides a presentation of situational awareness information for display that includes a compound symbol for each target spaced at a distance and bearing relative to a host symbol. The target compound symbol includes indicia of (a) whether the target is airborne or on the ground; (b) whether the target is a civil aircraft, a military aircraft identified as a formation member with the host aircraft, or a military aircraft not identified as a formation member with the host aircraft; (c) whether a ground track for the target is unknown, known by passive surveillance, or known by active surveillance; (d) for civil aircraft, whether the target is the subject of no advisory, a traffic advisory, or a resolution advisory; and (e) for a military aircraft, whether the target is the subject of no encroachment advisory, an unintended encroachment advisory, or an intended encroachment advisory. Subsystems selectively use an active or a passive mode of surveillance. In a passive mode, surveillance may rely on information received via a network among formation members and/or unsolicited received signals.