GNSS QUESTIONS AND ANSWERS
What does GNSS stand for? - Answer -Global Navigation Satellite Systems.
Name some GNSSs: - Answer -NAVSTAR (US); GLONASS (Russia); Galileo (Europe);
Beidou/ Compass (China).
What are the three segments of GNSS (3)? - Answer -1. Control segment
2. Space segment
3. User segment.
Describe the control segment (3). - Answer -1. Master control station.
2. 16 monitoring stations.
3. Monitors satellite orbits, health and sends commands.
Describe the space segment (5). - Answer -1. Min of 27 operation satellites.
2. Configured in 6 orbital planes.
3. Altitude of approx 20 200km.
4. 12hr earth orbit.
5. Onboard atomic clock.
Why are satellites at 20 200km? (3) - Answer -1. Survivability.
2. Accuracy.
3. Coverage.
Describe the user segment (2). - Answer -1. These are the users (all)/ receivers of the
system.
2. It is passive.
How does GNSS work (4)? - Answer -1. Multilateration.
2. Using 4 for 3D, 3 for 2D fix.
3. Satellites nag using time and ranging.
4. Velocity (speed of light) x travel time = distance.
What is multilateration? - Answer -The measurement of distance between 2+
known/unknown locations.
Radio frequencies. Describe the signal structure (2). - Answer -1. L1: Course
Acquisition code (CA); Precise (Encrypted) Code (P(Y)); Navigation message.
2. L2: P(Y) code; Nav msg.
What's in a nav msg (3)? - Answer -1. Ephemeris (orbit) / sat loc.
2. Almanac (forecast of sat's future loc).
3. Sat clock corrections.
What does GNSS stand for? - Answer -Global Navigation Satellite Systems.
Name some GNSSs: - Answer -NAVSTAR (US); GLONASS (Russia); Galileo (Europe);
Beidou/ Compass (China).
What are the three segments of GNSS (3)? - Answer -1. Control segment
2. Space segment
3. User segment.
Describe the control segment (3). - Answer -1. Master control station.
2. 16 monitoring stations.
3. Monitors satellite orbits, health and sends commands.
Describe the space segment (5). - Answer -1. Min of 27 operation satellites.
2. Configured in 6 orbital planes.
3. Altitude of approx 20 200km.
4. 12hr earth orbit.
5. Onboard atomic clock.
Why are satellites at 20 200km? (3) - Answer -1. Survivability.
2. Accuracy.
3. Coverage.
Describe the user segment (2). - Answer -1. These are the users (all)/ receivers of the
system.
2. It is passive.
How does GNSS work (4)? - Answer -1. Multilateration.
2. Using 4 for 3D, 3 for 2D fix.
3. Satellites nag using time and ranging.
4. Velocity (speed of light) x travel time = distance.
What is multilateration? - Answer -The measurement of distance between 2+
known/unknown locations.
Radio frequencies. Describe the signal structure (2). - Answer -1. L1: Course
Acquisition code (CA); Precise (Encrypted) Code (P(Y)); Navigation message.
2. L2: P(Y) code; Nav msg.
What's in a nav msg (3)? - Answer -1. Ephemeris (orbit) / sat loc.
2. Almanac (forecast of sat's future loc).
3. Sat clock corrections.
