Motion tracker

The Motion sensor, sometimes known as motion tracker, is a feature built into the heads-up display in the HRUNTING/YGGDRASIL Mark I Exoskeleton, the MJOLNIR armor and Sangheili combat harness. The sensor, located on the heads-up display's lower left corner, indicates individual allies, enemies and vehicles in relation to the location of the armor's operator.

Overview
The motion sensor is a circle with a central dot, which represents the user's location. The sensor shows individual allies as yellow dots and enemies as red dots. The size of the dot is depended on the size of the individual, with normal infantry represented by a normal dot, smaller life forms, such as rats, fishes, or even Flood infection forms, are represented by smaller dots, and large dots representing vehicles or large infantry, notably the Mgalekgolo. Unmanned vehicles appears as large gray dots.

Advantage
The motion sensor allows the user to locate enemies or allies behind cover, and is proved to be important for predicting enemy activities behind obstacles.

Disadvantage
The motion sensor is apparently be vulnerable to sea water, as indicated when Spartan-II Fred-104's motion tracker froze due to a crusting of sea salt. Equipments like Covenant radar jammer can be used to scramble the motion sensor's signal, effectively obliterating its use. The sensor is also shown to be susceptible to slow moving objects, which will not shown up on the motion sensor if within its range.

UNSC version
The first known UNSC motion sensor is integrated in the MJOLNIR Mark I exoskeleton. These exoskeletons never saw use in battle. The HRUNTING/YGGDRASIL Mark I Prototype Exoskeleton, which was developed in Algolis, included a 1400m+ sensor and a map mode. Unlike other iterations, enemies are indicated by short yellow lines.

The MJOLNIR Mark IV's heads-up display features a limited function motion sensor.

The prototype MJOLNIR Mark V includes a motion sensor with a radius of 25 meters. This motion sensor also takes into account vertical positioning. Allies, enemies, and vehicles will appear as properly colored triangles when they are a considerable height above, and appear as faded-out dots when they are a considerable height below. The radius of the motion sensor in the MJOLNIR Mark V's final iteration has been reduced by 10 meters, at only 15 meters.

The MJOLNIR Mark VI features motion sensors with the range of 20 or 25 meters, possibly depending on the operator's choice. Navigation points appear on the sides of the motion sensor as small white triangles.

Covenant version
The Sangheili seems to be the only Covenant species that included motion sensor into their armor. The Sangheili combat harness' motion sensor operates exactly like that of the MJOLNIR armor, having the inclusion of navigation points, verticality, and varying range.

Gameplay
In Halo 2, if a player were to look up or down, the motion sensor "plane" will adjust to be parallel to the player view, allowing them to see how far someone is above or below them. The Blind skull in campaign removes the entire HUD, including the motion sensor. In multiplayer, when the motion sensor is disabled through game settings, the sensor will remain on the HUD, but with an "X" above it.

In Halo 3 campaign, the Blind skull once again removes the motion sensor with the rest of the HUD, but the Fog skull removes only the motion sensor. In multiplayer, the motion sensor's range can be set to 15 meters, 25 meters, 50 meters, 75 meters or even 150 meters with blips becoming increasingly smaller the larger the range gets. During the game through Xbox LIVE, when an opposing team player speaks, their red blip is surrounded by a white glow and it becomes bigger.

In Halo: Reach, the Blind skull returns again and when activated, removes the entire HUD, including the motion sensor. The Fog skull, when activated, wields the same effect as Halo 3's Cloud skull, removing the motion sensor. The armor ability icon is then relocated from the top left of the motion sensor to the lower left of the HUD. In multiplayer, the motion sensor's lower right corner displays the name of the area the player is located in. This feature is absent in campaign, unless the player leaves the playable area, then the label is shown as "OUT OF BOUNDS".

Trivia

 * In Halo 2, if the player's energy shielding is critical, the motion sensor will flicker on and off.
 * The yellow dot at the center of the motion sensor's display is the player themselves. If the player isn't moving, this dot will disappear, then reappear once the player is moving with enough speed to register.
 * Vehicles that are moving, but are not currently manned (i.e. If someone jumps out of a Warthog that keeps moving), will appear as manned by a friendly.

List of appearances

 * Halo: The Fall of Reach
 * Halo: Combat Evolved
 * Halo 2
 * Halo: Ghosts of Onyx
 * Halo 3
 * Halo Legends
 * Prototype
 * The Package
 * Deliver Hope
 * Halo: Reach
 * Halo 4