Silent Cartographer

The Silent Cartographer, as referred to by the Covenant, is the map room for the Halo installations. It can pinpoint and access every room or location on or beneath Halo's surface.

Location on Installation 04
On Installation 04, the Cartographer was located in the middle of a large island. The security system was located in a tunnel, atop a large Forerunner structure in about the center of the island. After disabling the security system, the main passageway to the map room was opened. For additional security measures, the Cartographer's chamber and activation panel were located on the other side of the island, and buried at least half a dozen floors below ground. The path down to the Cartographer is a labyrinth of twists and turns, making it easy to get lost. This could also be part of the security system, to make the map room harder to find. It seems that on the map, the Control Room is illustrated as a shrine.

Security System
The Silent Cartographer is protected by an elaborate security system. This system can only be activated and deactivated by manual physical contact. In order to access the Silent Cartographer one must enter a first building to disable the security system, and then enter a separate structure which contains the map room. This gives the map room double protection making access difficult and defense much easier. The weaponry wielded by the crew of the Pillar of Autumn was not powerful enough to penetrate the doors inside the facility where the Silent Cartographer was located, indicating the doors were of extremely durable material. Other than near impenetrable doors, both physically and in protection against AI, the nature of the Silent Cartographer's security system is not touched upon in the game.

The Cartographer on the Ark has a similarly powerful security system, though it includes Sentinel patrols to further boost the defensive capabilities in the area. This proved to be most detrimental to the Covenant Loyalists, who had difficulty penetrating the Cartographer's defenses.

Battle of Installation 04
In 2552, John-117 and two squads of Marines were ordered by Captain Keyes to attack the Cartographer so that they could locate Halo's control room. The soldiers landed on a Covenant-controlled beach which was quickly captured. While taking shelter under an enormous structure, the Chief and his Marines received a Warthog from Echo 419. The Chief and two Marines used the Warthog to get to the entrance of the facility. The Chief captured the entrance but was locked out of the lower areas. The then went back to the Warthog and found the island's security center, guarded by many Covenant forces and an ambush by two Hunters orchestrated by Zuka 'Zamamee. After unlocking the map room, the Spartan headed back to the Cartographer and fought his way down to the map. Once on the surface again, the Chief went to the newly-located Control Room with the help of Echo 419.

Trivia

 * On the Halo 3 level The Ark, 343 Guilty Spark refers to the map on the Ark as "The Cartographer", but it is stated in The Silent Cartographer that it is the name that the Covenant uses for the map. Either the Covenant used the proper name for the map, or it is simply the shorter name for it.
 * The interior details and layout of the Cartographer on Installation 04 is almost completely identical to that of the Ark's Cartographer complex, though it is almost impossible to notice, due to the differences in textures, scenery, and atmosphere that were made to the structures to make them appear unique. In addition, practically the entire length from the first staircase to the main chamber of the Ark's Cartographer complex is a complete remake of Installation 04's Cartographer (with the exception of the added room for the Terminal)
 * The exterior appearance of the Installation 04 Cartographer was used for the design of the Ark's Cartographer. But, to differentiate the location of the Cartographer on the Ark with the one of Installation 04, the design of the main chamber in the one on Installation 04 is located almost directly underneath the ground of the deck entrance outside of the structure. However, the design of the Installation 04 Cartographer entrance was reused for the design of the Ark's Cartographer chamber. In addition, to make the similarities obscured, the platform holding the main chamber is surrounded by waterfalls.
 * The rock formation where the Dawn lands in the end of Halo 3 greatly resembles the Cartographer Island. However, this is likely just a homage, since the Control Room is very close to this hill.
 * The Silent Cartographer is oddly named because a cartographer is someone who makes maps, not a map itself. This may imply that the Silent Cartographer is more than just a building; possibly an old Forerunner computer.
 * It is unknown if all Forerunner structures have a Cartographer, though it is likely all Installations possess one.