Military Use of GPSMilitary Use of GPS

OverviewOverviewOverviewOverview

• Navigation Mission• GPS Segments• FBCB2• Summary

Navigation MissionNavigation MissionNavigation MissionNavigation Mission

Provide precise position, velocity, and time to users:

- Worldwide- Any weather

- 24 Hours/day

System SegmentsSystem SegmentsSystem SegmentsSystem Segments

Space Segment

User Segment

Control Segment

Space SegmentSpace SegmentSpace SegmentSpace Segment

• Block IIA - 7 1/2 year design life• Block IIR - 10 year design life• Launched by Delta II from Cape Canaveral

Space SegmentSpace SegmentSpace SegmentSpace Segment

• 24 satellites in constellation• 6 orbital planes, 4 satellites in each plane• 55 degree orbit inclination• Semisynchronous orbit

– 12 hour period– 12,500 statute miles (10,900 nm) altitude

• Constellation maximizes 3-D coverage– Ensures at least four satellites are visible to user anywhere in the

world (usually 6-7 visible)

Space SegmentSpace Segment(Constellation Phasing)(Constellation Phasing)

Space SegmentSpace Segment(Constellation Phasing)(Constellation Phasing)

The GPS constellation is designed to provide 24 hour coverage with graceful degradation.

Monitor Stations & Ground AntennasMonitor Stations & Ground AntennasMonitor Stations & Ground AntennasMonitor Stations & Ground Antennas

5 Monitor StationsCollect measurements from GPS satellites in view

5 Ground AntennasReceive/send TT&CUpdate NAV message and atomic clocks

Hawaii

ColoradoSprings

CapeCanaveral

AscensionIsland

DiegoGarcia

Kwajalein

The User SegmentThe User SegmentThe User SegmentThe User Segment

• Authorized Users: Military personnel, military systems, designated allies, and other authorized users

• Non-Authorized Users: Civilians and commercial firms around the world. Civilian and commercial users of GPS greatly outnumber those of the military, and the system is transitioning to allow Non-Authorized users greater accuracy.

GPS ServicesGPS ServicesGPS ServicesGPS Services

• Standard Positioning Service (SPS)– Intended for Non-Authorized Users– Provides decreased location and timing accuracy– Horizontal position within 100m or better (95%)– Timing accuracy within 340ns of UTC (95%)– Actual error based on current DoD Policy– Corrupts navigation signal by two methods

– Epsilon: changes the satellites position– Dither: changes the satellites time

• Precise Positioning Service (PPS)– Intended for Authorized (military) users– Provides very precise location and time accuracy– 3-D position within 16m Spherical Error Probability (50%)– Timing accuracy within 100ns of UTC – PPS is controlled by special crytographic keys

PLGR

TRIMPACK

Military GPS ReceiversMilitary GPS ReceiversMilitary GPS ReceiversMilitary GPS Receivers Small Lightweight GPS Receiver Small Lightweight GPS Receiver

(“Slugger”)(“Slugger”) Most Models SPSMost Models SPS Used during Desert StormUsed during Desert Storm

Precise Lightweight GPS Precise Lightweight GPS Receiver (“Plugger”)Receiver (“Plugger”) Standard Handheld UnitStandard Handheld Unit PPS CapablePPS Capable

Miniature Airborne Miniature Airborne GPS ReceiverGPS Receiver

Standard Aircraft Standard Aircraft UnitUnit

SLGR

PLGR

MAGR

Force XXI Battle Command Brigade and Below (FBCB2)Force XXI Battle Command Brigade and Below (FBCB2)OOverviewverview

Description:

• Forms the principal Digital Command and Control System for the Army at Brigade and Below

• Consists of hardware and software integrated into the various platforms at brigade and below, as well as appropriate Division and Corps slices necessary to support brigade operations

• Interconnects platforms through a communications infrastructure called the Tactical Internet consisting of existing EPLRS and SINCGARS Radio nets to pass Situation Awareness data and conduct Command and Control

2179 FBCB2 SystemsFielded to 4th for FDD

ONE PLATFORM’S WORTH OF FBCB2DIGITAL COMPONENTS SUPPORTING SITUATIONAL AWARENESS

AND COMMAND AND CONTROL

Hardware/Software

The FBCB2 hardware and software combine to provide the user with an integrated GIS system. The system allows users to manipulate map data, satellite photography, and digital elevation models. It also incorporates message capability. A key element of FBCB2 is Situational Awareness (SA). The software generates icons depicting actual units, vehicles, or soldiers deployed in the field.

PLGR GPS

GPS feeds directly into the FBCB2 computer thus giving precise locations to the user at all times. Because the GPS is completely integrated, the user can actively navigate off of the computer screen map. The GPS also provides a precise location for the user’s icon - generated by the FBCB2 hardware/software.

EPLRS VHSICSINCGARS SIP/INC

Radios (Single Channel Ground Airborne Radio System and the Enhanced Position Location Radio System) interlink multiple FBCB2s to form a larger network. This associated radio network enables the SA to be transmitted and shared between platforms and command posts.

Common Message Functions Common Message Functions ((CreateCreate//EditEdit//Send/ManageSend/Manage))

Common Message Functions Common Message Functions ((CreateCreate//EditEdit//Send/ManageSend/Manage))

Pull down menus allow the user to send various reports or build graphical overlays. When a report is sent, such as a Contact Report, the software automatically updates all other computers in the network with an enemy icon . Similarly, a commander can build a set of graphics depicting unit boundaries, friendly unit locations, known enemy locations, etc and quickly distribute this overlay around the battlefield.

Sending a message automatically updates all other FBCB2s in the network.

Combat Messages Combat Messages Spot ReportSpot Report

Combat Messages Combat Messages Spot ReportSpot Report

This sample report provides details pertaining to an enemy unit. Once again, information is automatically shared with all others.

Enemy location can be quickly entered by clicking the mouse cursor on the computer map where it is located.

Advantages and Disadvantages of GPSAdvantages and Disadvantages of GPS

• All-weather• Day and night• Worldwide direct downlink• Passive• Common grid• Restricted access• Survivable• Provides 3-D position and

velocity

• Dependent on ground stations• Jammable signal• Line of Sight from GPS

satellites

Advantages Limitations

SummarySummarySummarySummary

• GPS offers many advantages for navigation• The GPS system consists of a Space Segment, a Ground Segment,

and a User Segment• Selective Availability ensures Authorized users can receive a highly

accurate GPS signal while Non-Authorized users (potential adversaries) can be given a degraded signal

• The most common military GPS receiver is the PLGR, but many other receivers exist as well.

• GPS is evolving from a standalone capability into an integrated system called FBCB2.

• FBCB2 integrates GPS and a militarized GIS program to give commanders and soldiers increased situational awareness