CONTENTS (Continued)

Page

6.1.4.3

Failure Frequency Estimate...............................................................6 9

6.1.4.4

Failure Duration Estimate .................................................................6 9

6.1.4.5

Failure Magnitude and Behavior.....................................................6 10

6.1.4.6

User Global Distribution and Failure Visibility................................6 10

6.1.4.7

Satellite Use in the Position Solution ..............................................6 10

6.1.4.8

Failure Effect on Position Solution..................................................6 11

6.1.4.9

Expected Service Reliability Characteristics....................................6 11

6.1.5

Additional Commentary ..................................................................................6 11

6.1.5.1

24 Operational Satellites and Service Availability ...........................6 11

6.1.5.2

PDOP Less Than Six ......................................................................6 13

6.1.5.3

Four Satellite Solution and Five Degree Mask Angle.....................6 13

6.1.5.4

Integrity Checking...........................................................................6 14

6.1.5.5

Summary of the Commentary .........................................................6 15

6.2

Satellite Selection Criteria..............................................................................................6 15

6.2.1

Introduction.....................................................................................................6 15

6.2.2

Satellite Health ................................................................................................6 15

6.2.3

Geometric Dilution of Precision......................................................................6 16

6.2.4

User Range Accuracy......................................................................................6 16

6.2.5

Satellite Elevation Angle .................................................................................6 16

6.2.6

External Aids...................................................................................................6 16

6.3

Figure Of Merit (FOM) .................................................................................................6 17

CHAPTER 7:  AIDING OPTIONS FOR A GPS RECEIVER ..........................................................7 1

7.1

Types of Aiding ...............................................................................................................7 1

7.2

Aiding During Initial Acquisition .....................................................................................7 2

7.2.1

Position and Velocity Aiding.............................................................................7 2

7.2.2

Time Aiding.......................................................................................................7 2

7.2.3

Almanac Data....................................................................................................7 2

7.2.4

Effect On TTFF.................................................................................................7 2

7.3

Aiding to Translate Navigation Solution..........................................................................7 3

7.4

Aiding to Replace a Satellite Measurement......................................................................7 3

7.4.1

Clock Aiding .....................................................................................................7 4

7.4.2

Altitude Aiding..................................................................................................7 4

7.5

Aiding to Maintain Satellite Track...................................................................................7 4

CHAPTER 8:  POSSIBLE INTEGRATIONS OF GPS.....................................................................8 1

8.1

Introduction .....................................................................................................................8 1

8.2

Mission Requirements......................................................................................................8 2

8.3

Integration Architectures .................................................................................................8 3

8.3.1

GPS Stand Alone/Baro/Clock Aided................................................................8 3

8.3.2

GPS/INS Integrations .......................................................................................8 4

8.3.3

GPS and Mission Computer/Databus Emulator................................................8 5

8.3.4

GPS in a 1553 Databus Configuration ..............................................................8 5

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