GPS (Mechanic)
GPS (Global Positioning System) is a navigation system that is used to accurately determine the player aircraft position on a map and provide guidance to certain weapons in VTOL VR.
Systems that rely on GPS are susceptible to LOW band noise jamming, impacting both aircraft navigation as well as GPS-guided weapons.
GPS Page
The GPS page contains all functions for managing groups and points. Groups are a collection of points, useful for separation between different tasks or areas. Only the selected group will have its points visible on the NAV map.
- MAP: Shortcut to the NAV map page.
- WPT: Sets the selected point as the current NAV waypoint.
- PATH: Toggles the current group as a path. Required for certain munitions or NAV autopilot to navigate between multiple points.
- Up/Down Arrows: Moves the cursor for groups or points up and down.
- Up/Down Chevrons: Shifts the current point up or down in the list. Useful for correcting paths that are out of sequence.
- New Group: Creates a new empty group.
- Delete Group: Deletes the selected group.
- Delete Target: Deletes the selected point within its group.
- SEND: Only available in Multiplayer. Sends the current selected group to all other players on the team.
Creating GPS Points
Pilots can create their own points using the GPS-S (Send) function over either a locked target with the TSD, an area of interest with the NAV map, or either with the TGP. The NAV page also allows a certain altitude ASL to be set in increments of 250ft.
In Multiplayer, other players can share a GPS group with the team via the DataLink network. When received by another player, a new group will be added to the GPS page with their three letter identifier (first 3 letters of the sender's name).
GPS points can be automatically created by a mission event, for instance at mission start or after completing an objective. These groups have a "MSN" (Mission) identifier.
GPS Guided Munitions
There are 5 weapons in total that use GPS guidance:
- GBU-38 500lb Bombs
- GBU-39 206lb Glide Bombs
- AGM-161 Land-Attack Cruise Missile
- AGM-89 Anti-Ship Missile
- ADM-160J Miniature Air-Launched Decoy
The GBU-38 and GBU-39 can only use points, while the AGM-161, AGM-89, and ADM-160J can use the PATH function for more complex navigation.
When GPS reception is lost, such as during the effect of LOW band jamming, the aircraft will fall back to its inertial navigation system. The INS is responsible for keeping track of the aircraft's position using dead reckoning; i.e. using a last known position along with changes in accelerometers and gyroscopes to estimate position in real-time.
The INS slowly begins losing its accuracy as the aircraft maneuvers, a phenomenon known as INS drift. Over time the aircraft's indicated position and its actual position will deviate, causing elements like heading tape, NAV map, GPS points, and waypoint markers to appear misaligned in the world. Even a minute without GPS can cause guided munitions to miss their mark by a wide margin.
A Missile Warning Radar and GECM Truck can work in tandem to jam incoming GPS-guided projectiles and exploit their INS drift even after an accurate launch. The longer the weapon remains in flight, the more it will deviate off-course and more likely it will miss its target.
When GPS reception is regained, all GPS-related information will be corrected and the INS will automatically recalibrate itself.