Immersive Explanation: Alliances have Scouts.
Tired of being unable to find fights? Running up to empty keeps and playing PvDoor? Easily wiping the few that do come running to defend, only too late cause you already flipped it? A Heat Map overlay on the Cyrodiil map would give you a general location of medium to heavy concentrations of enemy players, so you can see in real time where the bulk of them are and you can maneuver accordingly, whether you want to avoid them, or charge. The overlay would also show us concentrations of friendly players, allowing solo players the opportunity to quickly find others to join on the field instead of spending the first twenty minutes at the gate spamming "lfg" in zone chat or sitting at an empty keep staring at the map waiting for another keep to flag so they know where to go next.
The Heat Map would not show the location of EVERY player. Solo and small groups would not show up on the map. Heat spots would only appear if the game registers 12 or more players within a certain radius of each other. In essence, Zergs could now be tracked to a general area.
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