Motion tracker

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Summary
Spartans and Elites have a Motion Tracking Sensor built into the HUD of their Helmets and Armor. The Sensor shows friendly's as yellow blips and friendly vehicles as large yellow blips. Enemies on the other hand are shown as red blips, Hunters and enemy vehicles as large red blips. The Motion Tracker will show how close they are in relation to your current position. When someone on the other team in multiplayer speaks, their red blip gets white around it and becomes bigger.

Remember it is a Motion Tracker not a Radar. Slow moving enemies will not show up on the Sensor. This can work to your advantage of course, moving very slowly or crouch walking will mean you won't show up on enemies Motion Trackers.