GPS

Question 1

What are the 3 major segments of a satellite

Answer 1

Space segment = satellite

Control segment = ground monitoring station

User segment = GPS receiver

Question 2

What does the ground control segment of the GPS satellites do

Answer 2

Monitors the satellites, calculates corrections and transmits them to satellites

1 master control and several monitors positioned close to the equator

Question 3

How many satellites does NAVSTAR have

Answer 3

24 satellites

21 operational
3 spare

Question 4

How many different orbital patterns does NAVSTAR have

Answer 4

6

Question 5

What is the height of navstar orbits

Answer 5

20,200km

Question 6

What incline is the NAVSTAR orbits to the equator

Answer 6

55°

Question 7

How long is a NAVSTAR orbit

Answer 7

12 hours

Question 8

What are the frequencies for NAVSTAR

Answer 8

Link 1 = 1575.42mhz

Link 2 = 1227.6mhz

Question 9

Why is there 2 link frequencies for gps

Answer 9

Estimate ionosphere delay

Question 10

What transmits the course acquisition code

Answer 10

Link one

Associated with sps service
Standard positioning service

Question 11

What are the modes of operation for GPS

Answer 11

Standard positioning service (SPS) for civilian users = L1

Precise position service (PPS) for military users = L2

Question 12

What is the reference datum for NAVSTAR

Answer 12

World geodetic system 1984

Question 13

What is the user segment of a gps

Answer 13

Any capable satellite receiver

Question 14

What gps is a civilian receiver capable of receiving

Answer 14

L1 = course acquisition / selected availability

Question 15

What is a military GPS receiver able to receive

Answer 15

Both L1 and L2 signals with a P code (precision)

Question 16

What is a satellite gps principle of operation

Answer 16

TIME

broadcast ranging codes and accurate times

Receiver measures signal transmit time to determine range from satellite

Question 17

What gps location can a position from one satellite give you

Answer 17

A position on the surface of a sphere

Question 18

What gps location can a position from two satellite give you

Answer 18

Produce a circular position line where the 2 spheres intersect

Question 19

What gps location can a position from three satellite give you

Answer 19

Unambiguous position

Question 20

What gps location can a position from four satellite give you

Answer 20

Unambiguous fix with all timing errors resolved

Question 21

What is the max number of users on a gps satellite

Answer 21

Unlimited number of users

Question 22

How is pseudo range countered

Answer 22

Due to timing error = range error

Therefor

Resolved by receiver clocks being a little slower so that range is always overestimated

Question 23

How is receiver clock error corrected for gps

Answer 23

With signals from 4 satellites

Question 24

What does ephemeris data (almanac info) contain

Answer 24

Accurate satellite orbit info

Question 25

What is the optimum satellite position

Answer 25

One directly above 3 = 120° apart

Question 26

``` How long does it take to download Ephemeris info Ionosphere delay Timing info Satellite health ```

Answer 26

12.5 mins

Question 27

What is the time difference between Utc and satellite clock

Answer 27

13.5 seconds

Question 28

How accurate is the satellite atomic clocks

Answer 28

1 nanosecond

Question 29

What is the GPS receiver used in aircraft

Answer 29

Multi channel receivers

Question 30

What is the biggest error in gps

Answer 30

Ionospheric propagation delay IPD = 5m

Question 31

What is masking angle

Answer 31

Gps just disappears behind horizon

Question 32

What is RAIM

Answer 32

Receiver autonomous integrity monitoring Checks integrity of what is displayed Required for GNSS aviation Required min of 5 usable satellites to allow swapping to maintain a 3D fix RAIM with spare facility would require 6 satellites

Question 33

What is GBAS

Answer 33

Ground based augmentation systems Also known as local area differential gps (LADGPS) Employs a local augmentation system (LAAS) Allows; Precision approach service GBAS position service Uses satellite close to airfield to adjust correction errors from gps and send these corrections to aircraft via VHF

Question 34

What is GRAS

Answer 34

Ground regional augmentation system GBAS with more pseudo satellites Increases accuracy

Question 35

What is SBAS

Answer 35

Satellite based augmentation systems Wide area differential gps (WADGPS) At best can give CAT 1 approach Has control stations on the ground which asses the errors in gps positions which is sent to the satellites to correct

Question 36

What is EGNOS

Answer 36

European geostationary navigation overlay system Geostationary satellite

Question 37

What is WAAS

Answer 37

Wide area augmentation system Operates by USA Geostationary satellite

Question 38

What is MSAS

Answer 38

Multi function transport satellite augmentation system Operates by japan Geostationary satellite

Question 39

What is GAGAN

Answer 39

Gel and gps augmented navigation Operated by India Geostationary satellite

Question 40

What is ABAS

Answer 40

basically RAIM

Question 41

What is GLONASS

Answer 41

Old system resurrected by Russia Fully operational by 2010 Uses Pz-90 datum Been used since 2007 Integrity implemented by SBAS / GBAS

Question 42

What are the frequencies for GLONASS

Answer 42

L1 1.6GHZ | L2 1.2GHZ

Question 43

What is GALILEO

Answer 43

European system Not operational yet Estimated 2020

Question 44

What are the GALILEO clocks made out of

Answer 44

Rubidium frequency standard clock Very accurate passive hydrogen master clock

Question 45

What does he signal generation section of GALILEO contain

Answer 45

Message comprises ephemeris and orbit info and clock references

Question 46

What are the GALILEO frequencies

Answer 46

``` L1 = 1164-1215 MHZ L2 = 1260-1300 MHz L3 = 1559 - 1571 MHz ``` L3 shares with gps on a non interference basis