Global Positioning System (GPS)

Question 1

What is GNSS?

Answer 1

Global Navigation Satellite System
A generic term for satellite navigation

Question 2

The United States Global Positioning System is one form of?

Answer 2

GNSS

Question 3

Satellite Navigation offers what?

Answer 3

a level of precision that no other system can provide

Question 4

Each GPS satellite carries at least:

Answer 4

two atomic clocks, which measure the movement of elements like rubidium or cesium.

Question 5

The GPS clock onboard the aircraft is what style?

Answer 5

simple quartz style

Question 6

The accuracy of this clock is controlled by:

Answer 6

signals it receives from the GPS satellite

Question 7

Clocks are the key to providing:

Answer 7

an accurate fix of position for the aircraft

Question 8

Navstar Satellite System is known as what?

Answer 8

Time Delay Navigation

Question 9

The position of the Navstar Satellite System can be determined by:

Answer 9

estimating when the LOPs cross

Question 10

What does LOP stand for?

Answer 10

Lines of Position

Question 11

The crossing points of the LOPs can be converted to:

Answer 11

the coordinate system of latitude, longitude, and altitude

Question 12

In GNSS the navigation transmitters are the:

Answer 12

satellites or Space Vehicles (SV)

Question 13

The more Space Vehicles (SV) that the receiver can “see”, the more what?

Answer 13

accurate the position fix

Question 14

GPS consists of:

Answer 14

24 satellites in 6 orbital planes

Question 15

There are three segments to the GPS system:

Answer 15

The Control Segment
The Space Segment
The User Segment

Question 16

What does the Control Segment monitor?

Answer 16

satellite operation
Controls the SV’s and uploads information

Question 17

What is the Space Segment?

Answer 17

the SV’s

Question 18

What is the User Segment?

Answer 18

the pilots (receivers) who use the GPS to navigate

Question 19

The L1 frequency is 1574.20 MHz and is used by:

Answer 19

the civilian user segment for position determine

Question 20

The L2 frequency is 1227.60MHz and is currently used by:

Answer 20

the US military to measure errors caused by the ionosphere

Question 21

The third frequency is the L5 or 117.45MHz and is protected worldwide for aeronautical radio navigation use. The addition of L5 will make GPS:

Answer 21

a more robust radio navigation service for many aviation applications as well as all ground based users

Question 22

C/A code is also called:

Answer 22

a Pseudo Random Noise (PRN) code and repeats 1,023 bits each millisecond

Question 23

The PRN is unique to:

Answer 23

each SV and is used for its identification

Question 24

The L1 frequency also carries a navigation message containing bits of data. The navigation message builds the:

Answer 24

Almanac

Question 25

The Almanac contains data about:

Answer 25

errors and ephemerides

Question 26

What is an Ephemerid?

Answer 26

a small distortion in the orbit of an SV which can cause errors in position

Question 27

A GPS receiver must have what?

Answer 27

a current almanac, including ephemeris data, to navigate properly

Question 28

Exact distance between the GPS SV’s and the receiver is:

Answer 28

impossible to determine

Question 29

The GPS receiver is able to best calculate position when?

Answer 29

the SV’s are widespread

Question 30

Error based on lines of position angles is known as:

Answer 30

Geometric Dilution of Precision or GDOP

Question 31

In worst case situation, GPS accuracy is:

Answer 31

100m laterally and 156m vertically

Question 32

GPS accuracy can be increased by using:

Answer 32

a ground based augmentation system (GBAS)

Question 33

When did the Wide Area Augmentation System (WAAS) come into use?

Answer 33

2003

Question 34

A typical specification for a WAAS corrected GPS position is:

Answer 34

1m lateral and 2m vertical

Question 35

WAAS provides an accuracy for aircraft to conduct precision approaches bearing or at:

Answer 35

minimum altitudes CAT I approaches

Question 36

LAAS service is focused within 20-30 miles of the airport and has an accuracy of:

Answer 36

less than 1m, CAT I, II, III

Question 37

GPS receivers without GBAS use the:

Answer 37

Receiver Autonomous Integrity Monitoring (RAIM)

Question 38

RAIM monitors the:

Answer 38

pseudo range measurements of at least 6 SV’s

Question 39

If one or more of the pseudo range measurements does not agree, what happens?

Answer 39

a RAIM alarm will be sent

Question 40

WAAS and LAAS eliminate RAIM requirements by:

Answer 40

allowing the system to alert the pilot within 6 to 8 seconds of fault detection

Question 41

What does Fault Detection Exclusion (FDE) do?

Answer 41

Analyzes the RAIM alarm to determine which SV is causing the problem. Once analyzed it automatically excludes the faulty SV from the navigation calculations

Question 42

A crucial element of the system is the:

Answer 42

GPS database

Question 43

The database may be contained in a:

Answer 43

user replaceable memory card, or be updated via a data port

Question 44

What is Galileo?

Answer 44

the European GNSS

Question 45

What is GLONASS?

Answer 45

the Russian abbreviation for GNSS

Question 46

GPS Flight Line Testing must be accomplished outside so that:

Answer 46

the receiving antenna can “see” the SV’s

Question 47

How can you test the GPS if the aircraft cannot be moved or the sky is not clear enough for a good signal?

Answer 47

there are ramp test simulators to test the receiver