INRAT – GNSS EXAM QUESTIONS
AND ANSWERS
GNSS stands for - Correct Answers -Global Navigation Satellite System
How do GNSS and GPS relate? - Correct Answers -GPS is the U.S. GNSS system
GPS based on GNSS is approved for aviation use ONLY
The GPS constellation contains _______ satellites which orbit the earth _____ times
per day each at an altitude of __________ NM (_________km) - Correct Answers -24
twice a day
10,900 NM
20,200 KM
GPS satellites are arranged in _____ separate orbital planes which ____ satellites on
each plane - Correct Answers -6 orbital planes
4 satellites each
How many satellites are required for 3D navigation? - Correct Answers -4
How many satellites are required for 2D navigation? - Correct Answers -3
How does GPS work? - Correct Answers -A GPS receiver determines a three-
dimensional position in space by calculating multiple ranges from at least four satellites.
GPS accuracy depends on what? - Correct Answers -Transit time and signal
propagation speed to compute pseudoranges and relative position of satellites in the
sky (satellite geometry)
What is the ionosphere? How does this affect GPS? - Correct Answers -A zone of
charged particles several hundred km above the earth
Causes signal delays that vary from day to night and by solar acticvity
GPS horizontal and vertical positions are accurate to _____ and _____, _____% of the
time - Correct Answers -6-8m 95% of the time
, Why is Augmentation of GPS required? What are the 3 types? - Correct Answers -
Required to meet the accuracy, integrity, continuity and availability for aviation
1. Aircraft-based augmentation system (ABAS)
2. Satellite based augmentation system (SBAS)
3. Ground based augmentation system (GBAS)
RAIM stands for? - Correct Answers -Receiver Autonomous Integrity Monitoring
It takes ____ satellites to compute a navigation solution and a minimum of _____ for
RAIM to function - Correct Answers -4
5
What is the applicable alert limit of RAIM?
Enroute
Terminal
NPA
What happens if it is outside this range?
Will it continue functioning? - Correct Answers -2NM enroute
1NM terminal
0.3NM NPA
= If outside this range, RAIM is unable to guarantee the integrity of the position solution
It will continue functioning but pilots should discontinue the use of GNSS unless in an
emergency
If you see red flags on the HSI or CDI when in RAIM, what does this mean? - Correct
Answers -The avionics detects a satellite range error (typically caused by satellite
malfunction) that may cause an accuracy degradation that exceeds the alert limit
It will continue functioning but pilots should discontinue the use of GNSS unless in an
emergency
FDE? - Correct Answers -Fault Detection and Exclusion
Allows the avionics to detect which satellite is faulty and exclude it from the navigation
solution
FDE requires how many satellites? - Correct Answers -6
AND ANSWERS
GNSS stands for - Correct Answers -Global Navigation Satellite System
How do GNSS and GPS relate? - Correct Answers -GPS is the U.S. GNSS system
GPS based on GNSS is approved for aviation use ONLY
The GPS constellation contains _______ satellites which orbit the earth _____ times
per day each at an altitude of __________ NM (_________km) - Correct Answers -24
twice a day
10,900 NM
20,200 KM
GPS satellites are arranged in _____ separate orbital planes which ____ satellites on
each plane - Correct Answers -6 orbital planes
4 satellites each
How many satellites are required for 3D navigation? - Correct Answers -4
How many satellites are required for 2D navigation? - Correct Answers -3
How does GPS work? - Correct Answers -A GPS receiver determines a three-
dimensional position in space by calculating multiple ranges from at least four satellites.
GPS accuracy depends on what? - Correct Answers -Transit time and signal
propagation speed to compute pseudoranges and relative position of satellites in the
sky (satellite geometry)
What is the ionosphere? How does this affect GPS? - Correct Answers -A zone of
charged particles several hundred km above the earth
Causes signal delays that vary from day to night and by solar acticvity
GPS horizontal and vertical positions are accurate to _____ and _____, _____% of the
time - Correct Answers -6-8m 95% of the time
, Why is Augmentation of GPS required? What are the 3 types? - Correct Answers -
Required to meet the accuracy, integrity, continuity and availability for aviation
1. Aircraft-based augmentation system (ABAS)
2. Satellite based augmentation system (SBAS)
3. Ground based augmentation system (GBAS)
RAIM stands for? - Correct Answers -Receiver Autonomous Integrity Monitoring
It takes ____ satellites to compute a navigation solution and a minimum of _____ for
RAIM to function - Correct Answers -4
5
What is the applicable alert limit of RAIM?
Enroute
Terminal
NPA
What happens if it is outside this range?
Will it continue functioning? - Correct Answers -2NM enroute
1NM terminal
0.3NM NPA
= If outside this range, RAIM is unable to guarantee the integrity of the position solution
It will continue functioning but pilots should discontinue the use of GNSS unless in an
emergency
If you see red flags on the HSI or CDI when in RAIM, what does this mean? - Correct
Answers -The avionics detects a satellite range error (typically caused by satellite
malfunction) that may cause an accuracy degradation that exceeds the alert limit
It will continue functioning but pilots should discontinue the use of GNSS unless in an
emergency
FDE? - Correct Answers -Fault Detection and Exclusion
Allows the avionics to detect which satellite is faulty and exclude it from the navigation
solution
FDE requires how many satellites? - Correct Answers -6
