GPS

Question 1

How does GPS operate

Answer 1

It measures the time from when a radio wave is sent from a satellite to when it is received by an a/c

Question 2

What are the 3 segments of GPS

Answer 2

Space
Ground
User

Question 3

With regards to GPS, what happens with:
1-Coarse acquisition code
2-Precision code

Answer 3

1-the CA code modulates the carrier at 1.023MHz, taking the form of randomly spaced set of pulses generated for one millisecond. Same set of pulses repeated every millisecond
2-P code is 10MHz PRN code with 7 day cycle. P code is modulated on L1 and L2 frequencies allowing for Ionospheric delay correction

Question 4

What are the following used for in GPS
1-Coarse Aquisition code
2-Precision code

Answer 4

1-standard position services (SPS)
2-precise position service (PPS)

Question 5

What process do GPS systems use to modulate carrier frequencies

Answer 5

Phase modulation

Question 6

1-what is jittering
2-What is the effect of gittering a GPS signal

Answer 6

1-altering the timing of a satellite in a random fashion
2-it improves the accuracy of the info received by the a/c receiver

Question 7

What type of fix do the following satellite configurations provide
1-three satellite fixing
2-four satellite fixing
3-how is velocity measured

Answer 7

1-a 2D fix
2-a 3D fix
3-velocity of a/c is measured by instantaneous doppler shift at a/c

Question 8

What is Recevier Autonomous Integrity Monitoring - RAIM

Answer 8

If one of four satellites provides erroneous info to a/c, the pos calculated will be wrong and won’t be detected until the ground station updates the satellite.
Using different combinations of 4 satellites, the position calculations can be compared, and the faulty satellite eliminated

Question 9

What is GPS Integrity Broadcast - GIB

Answer 9

A ground based satellite monitoring system that measures satellite range on a continuous basis and uses the measured values to compute and broadcast range errors

Question 10

What is Dilution of Precision (DOP)

Answer 10

A loss of accuracy due to relative position of visible satellites

Question 11

How does GLONASS differ from NAVSTAR GPS systems

Answer 11

Their satellites are in lower orbit

Question 12

What is a task of the space segment of a GPS system

Answer 12

Transmit signals that can be used by receivers to determine time, position and velocity

Question 13

What are the contents of the navigation and systems messages from a GPS

Answer 13

Satellite clock error
Almanac data
Ionospheric propagation info

Question 14

What is the function of the receiver in the GNSS user segment

Answer 14

To track the satellites to calculate range

Question 15

What frequency does GPS operate

Answer 15

UHF at 1575.42MHz

Question 16

How high above the horizon must satellites be in order to be in view for SPS

Answer 16

5° or higher

Question 17

What does GBAS positioning system provide

Answer 17

Horizontal position info to support RNAV approaches in terminal areas

Question 18

What is Almanac data in receivers of satellites used for

Answer 18

Fast ID of received signals from available satellites

Question 19

In the NAVSTAR/GPS satellite navigation system, what is the maximum time taken to receive the complete set of almanac data from all satellites

Answer 19

12.5 minutes, 30 seconds for each data frame