UAG Navigation and GPS Systems 1 — Questions and Answers
Question 1: What minimum number of GPS satellites must a receiver have line-of-sight to in order to calculate a three-dimensional position fix?
- 2 satellites
- 3 satellites
- 4 satellites (Correct answer)
- 6 satellites
Correct answer: 4 satellites
A GPS receiver needs signals from at least 4 satellites to calculate latitude, longitude, altitude, and time simultaneously for a 3D position fix.
Question 2: What does WAAS stand for in the context of GPS navigation?
- Wide Area Augmentation System (Correct answer)
- Waypoint Accuracy Automation System
- Wireless Aerial Azimuth System
- Wide Angle Altimeter Standard
Correct answer: Wide Area Augmentation System
WAAS (Wide Area Augmentation System) is an FAA satellite-based augmentation system that improves GPS accuracy for aviation use to approximately 1–3 meters.
Question 3: Which FAA publication would a remote pilot check to learn about scheduled GPS signal outages or testing in a specific area?
- Airport/Facility Directory (A/FD)
- NOTAMs (Notices to Air Missions) (Correct answer)
- Aeronautical Information Manual (AIM)
- Aviation Weather Services AC 00-45
Correct answer: NOTAMs (Notices to Air Missions)
NOTAMs (Notices to Air Missions) are used to inform pilots, including remote pilots, of GPS anomalies, outages, and testing affecting navigation.
Question 4: Magnetic variation (declination) is best defined as:
- The difference in GPS accuracy between day and night
- The angular difference between true north and magnetic north at a given location (Correct answer)
- The compass error caused by nearby metal in an aircraft
- The deviation of GPS coordinates from actual position
Correct answer: The angular difference between true north and magnetic north at a given location
Magnetic variation is the angular difference between true geographic north and magnetic north, which varies by location and changes slowly over time.
Question 5: What is Receiver Autonomous Integrity Monitoring (RAIM)?
- A system that automatically updates GPS firmware
- A GPS feature that allows receivers to detect faulty satellite signals (Correct answer)
- A backup radio navigation system used when GPS fails
- A regulatory requirement for UAS GPS equipment
Correct answer: A GPS feature that allows receivers to detect faulty satellite signals
RAIM is a GPS receiver function that cross-checks multiple satellite signals to detect and exclude faulty signals, providing integrity monitoring without external input.
Question 6: When a UAS operating in GPS-assisted flight mode suddenly loses its GPS signal, what is the most likely immediate response of a standard autopilot system?
- The UAS will immediately return to home automatically
- The UAS will switch to attitude/manual mode and may drift with wind (Correct answer)
- The UAS will land autonomously at its current location
- The UAS will hover indefinitely without any movement
Correct answer: The UAS will switch to attitude/manual mode and may drift with wind
Most UAS autopilots transition to attitude (stabilized) mode when GPS is lost, meaning the aircraft can maintain attitude but will drift with wind since there is no position hold.
Question 7: On a VFR sectional chart, what do isogonic lines represent?
- Lines connecting points of equal barometric pressure
- Lines connecting points of equal magnetic variation (Correct answer)
- Lines connecting airports at the same elevation
- Lines connecting points with identical wind speeds
Correct answer: Lines connecting points of equal magnetic variation
Isogonic lines on sectional charts connect points of equal magnetic variation (declination), helping pilots convert between true and magnetic headings.
UAG Navigation and GPS Systems 1
What minimum number of GPS satellites must a receiver have line-of-sight to in order to calculate a three-dimensional position fix?