Navigation and GPS Systems Flashcards
7 cards from real UAG practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Navigation and GPS Systems flashcards as text
GPS signal multipath error occurs when:
Answer: The GPS signal reflects off surfaces before reaching the receiver
Multipath error occurs when GPS signals reflect off buildings, terrain, or other surfaces before reaching the receiver, causing inaccurate position calculations.
What is Position Dilution of Precision (PDOP) in GPS navigation?
Answer: The reduction in GPS accuracy caused by poor satellite geometry
PDOP quantifies how the geometric arrangement of visible satellites affects position accuracy; a low PDOP (under 4) means favorable satellite geometry and better accuracy.
Which type of GPS interference involves intentionally broadcasting false GPS signals to mislead receivers?
Answer: GPS spoofing
GPS spoofing is the deliberate transmission of counterfeit GPS signals to deceive receivers into calculating false position, velocity, or time information.
When converting a true course to a magnetic course, a pilot in an area with 10° East magnetic variation should:
Answer: Subtract 10° from the true course
With East variation, subtract the variation from the true course to obtain the magnetic course (East is least — subtract; West is best — add).
What is dead reckoning as applied to UAS navigation?
Answer: Estimating position using last known position, speed, heading, and elapsed time
Dead reckoning involves calculating a current position estimate based on a previously known position, applying known speed, heading, and time elapsed since that position.
Ionospheric disturbances (such as solar flares) primarily affect GPS signals by:
Answer: Causing signal delays that introduce position errors
Solar activity causes the ionosphere to vary, which changes the speed of GPS radio waves passing through it, introducing timing errors that translate into position inaccuracies.
A UAS remote pilot notices the aircraft's GPS-based position display shows a location 50 meters from the actual position. What is the most likely cause?
Answer: Poor satellite geometry (high PDOP) or signal multipath
Large position errors are most commonly caused by poor satellite geometry (high PDOP) or multipath interference from reflective surfaces near the operating area.