From Halopedia, the Halo wiki
A tactical map (TACMAP) are virtualized maps utilized by personnel of the UNSC Armed Forces. TACMAPs display information on terrain and geography, provided by satellite imagery and topographic surveys. Accessible through data pads or heads-up displays, these maps can be interfaced with navigation markers to identify targets, and relevant data can be shared through the UNSC battle network. A unit's TACMAP is maintained by an intelligence squad, responsible for gathering new data with reconnaissance drones and establishing TACMAP linkups to HUDs.
TACMAP can be used to identify allies and squadmates, with teammates transmitting their locating to their unit through TACMAP. Hostiles appear through TACMAP in the form of red ovals. Mission objectives are also stored with TACMAP. TACMAPs are primarily used by Spartans, integrated into the HUD interface of the MJOLNIR Powered Assault Armor or Semi-Powered Infiltration Armor. A similar navigation feature can also be used by the Orbital Drop Shock Troopers, as a component of the VISR system in their armor.
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