GNSS - GLOBAL NAVIGATION SATELLITE SYSTEM | LATEST
EXAM QUESTIONS WITH VERIFIED ANSWERS - UPDATED
2026/2027
Global Navigation Satellite System - GNSS
1. Q: What does GNSS stand for? ANSWER Global Navigation Satellite
System.
2. Q: What is the difference between GNSS and GPS? ANSWER GNSS is the
generic term for all satellite navigation systems; GPS is the specific US
system.
3. Q: What are the four major global GNSS constellations? ANSWER GPS
(US), GLONASS (Russia), Galileo (EU), BeiDou (China).
4. Q: What is the basic principle of GNSS positioning? ANSWER
Trilateration (determining position based on distances from multiple
satellites).
5. Q: How many satellites are minimally required for a 2D position fix?
ANSWER 3 satellites.
6. Q: How many satellites are minimally required for a 3D position fix
(latitude, longitude, altitude)? ANSWER 4 satellites.
7. Q: Why is a 4th satellite required for a 3D fix? ANSWER To resolve the
receiver's clock bias (offset from satellite atomic time).
8. Q: What is a pseudorange? ANSWER The apparent distance from a
satellite to a receiver, calculated from signal travel time, but containing a
clock error.
,9. Q: What is the speed of radio waves used in GNSS calculations?
ANSWER The speed of light (approximately 299,792,458 meters per
second).
10.Q: What type of clocks do GNSS satellites use? ANSWER Highly precise
atomic clocks (Cesium and Rubidium).
11.Q: Why are atomic clocks necessary on satellites? ANSWER Because a
timing error of just 1 microsecond equals a 300-meter positioning error.
12.Q: What is an almanac in GNSS? ANSWER A dataset containing coarse
orbital parameters and health status for all satellites in the constellation.
13.Q: What is ephemeris data? ANSWER Precise orbital parameters for a
specific satellite used to calculate its exact position.
14.Q: How often is ephemeris data typically updated? ANSWER Every 2
hours for GPS; valid for about 4 hours.
15.Q: What is TTFF? ANSWER Time To First Fix, the time it takes a receiver
to acquire signals and calculate a position.
16.Q: What causes a "cold start" TTFF? ANSWER The receiver has no
almanac, ephemeris, time, or position data; it must search blindly.
17.Q: What is a "warm start" TTFF? ANSWER The receiver has a valid
almanac and approximate time/position, but needs new ephemeris data.
18.Q: What is a "hot start" TTFF? ANSWER The receiver has valid almanac,
ephemeris, time, and position; fix is almost immediate.
19.Q: What is Dilution of Precision (DOP)? ANSWER A mathematical
measure of the geometric effect of satellite positions on positioning
accuracy.
20.Q: What is GDOP? ANSWER Geometric Dilution of Precision (overall 3D
plus time).
21.Q: What is PDOP? ANSWER Position Dilution of Precision (3D).
22.Q: What is HDOP? ANSWER Horizontal Dilution of Precision
(latitude/longitude).
23.Q: What is VDOP? ANSWER Vertical Dilution of Precision (altitude).
, 24.Q: Does a lower DOP value indicate better or worse accuracy? ANSWER
Better accuracy (satellites are spread out).
25.Q: What causes a high DOP? ANSWER Satellites clustered in a small
area of the sky.
26.Q: What is the maximum operational altitude for standard GNSS
receivers? ANSWER Typically 18,000 m (60,000 ft) or 515 m/s velocity
due to ITAR regulations.
27.Q: What is the typical altitude of GNSS satellites? ANSWER Medium
Earth Orbit (MEO), roughly 20,000 to 23,000 km.
28.Q: What is a GNSS "window"? ANSWER The set of satellites currently
visible above the horizon to a receiver.
29.Q: What does COG stand for? ANSWER Course Over Ground.
30.Q: What does SOG stand for? ANSWER Speed Over Ground.
31.Q: What does GPS stand for? ANSWER Global Positioning System.
32.Q: Who owns and operates GPS? ANSWER The United States Space
Force (formerly Air Force).
33.Q: When was GPS declared fully operational? ANSWER 1995.
34.Q: What was the original name of GPS? ANSWER NAVSTAR (Navigation
System Using Timing And Ranging).
35.Q: How many satellites make up the baseline GPS constellation?
ANSWER 24.
36.Q: How many orbital planes does GPS have? ANSWER 6.
37.Q: How many satellites are in each GPS orbital plane? ANSWER 4 (with
spares).
38.Q: What is the orbital inclination of GPS satellites? ANSWER 55 degrees.
39.Q: What is the exact orbital altitude of GPS satellites? ANSWER 20,200
km.
40.Q: What is the orbital period of GPS satellites? ANSWER Approximately
11 hours, 58 minutes (half a sidereal day).
EXAM QUESTIONS WITH VERIFIED ANSWERS - UPDATED
2026/2027
Global Navigation Satellite System - GNSS
1. Q: What does GNSS stand for? ANSWER Global Navigation Satellite
System.
2. Q: What is the difference between GNSS and GPS? ANSWER GNSS is the
generic term for all satellite navigation systems; GPS is the specific US
system.
3. Q: What are the four major global GNSS constellations? ANSWER GPS
(US), GLONASS (Russia), Galileo (EU), BeiDou (China).
4. Q: What is the basic principle of GNSS positioning? ANSWER
Trilateration (determining position based on distances from multiple
satellites).
5. Q: How many satellites are minimally required for a 2D position fix?
ANSWER 3 satellites.
6. Q: How many satellites are minimally required for a 3D position fix
(latitude, longitude, altitude)? ANSWER 4 satellites.
7. Q: Why is a 4th satellite required for a 3D fix? ANSWER To resolve the
receiver's clock bias (offset from satellite atomic time).
8. Q: What is a pseudorange? ANSWER The apparent distance from a
satellite to a receiver, calculated from signal travel time, but containing a
clock error.
,9. Q: What is the speed of radio waves used in GNSS calculations?
ANSWER The speed of light (approximately 299,792,458 meters per
second).
10.Q: What type of clocks do GNSS satellites use? ANSWER Highly precise
atomic clocks (Cesium and Rubidium).
11.Q: Why are atomic clocks necessary on satellites? ANSWER Because a
timing error of just 1 microsecond equals a 300-meter positioning error.
12.Q: What is an almanac in GNSS? ANSWER A dataset containing coarse
orbital parameters and health status for all satellites in the constellation.
13.Q: What is ephemeris data? ANSWER Precise orbital parameters for a
specific satellite used to calculate its exact position.
14.Q: How often is ephemeris data typically updated? ANSWER Every 2
hours for GPS; valid for about 4 hours.
15.Q: What is TTFF? ANSWER Time To First Fix, the time it takes a receiver
to acquire signals and calculate a position.
16.Q: What causes a "cold start" TTFF? ANSWER The receiver has no
almanac, ephemeris, time, or position data; it must search blindly.
17.Q: What is a "warm start" TTFF? ANSWER The receiver has a valid
almanac and approximate time/position, but needs new ephemeris data.
18.Q: What is a "hot start" TTFF? ANSWER The receiver has valid almanac,
ephemeris, time, and position; fix is almost immediate.
19.Q: What is Dilution of Precision (DOP)? ANSWER A mathematical
measure of the geometric effect of satellite positions on positioning
accuracy.
20.Q: What is GDOP? ANSWER Geometric Dilution of Precision (overall 3D
plus time).
21.Q: What is PDOP? ANSWER Position Dilution of Precision (3D).
22.Q: What is HDOP? ANSWER Horizontal Dilution of Precision
(latitude/longitude).
23.Q: What is VDOP? ANSWER Vertical Dilution of Precision (altitude).
, 24.Q: Does a lower DOP value indicate better or worse accuracy? ANSWER
Better accuracy (satellites are spread out).
25.Q: What causes a high DOP? ANSWER Satellites clustered in a small
area of the sky.
26.Q: What is the maximum operational altitude for standard GNSS
receivers? ANSWER Typically 18,000 m (60,000 ft) or 515 m/s velocity
due to ITAR regulations.
27.Q: What is the typical altitude of GNSS satellites? ANSWER Medium
Earth Orbit (MEO), roughly 20,000 to 23,000 km.
28.Q: What is a GNSS "window"? ANSWER The set of satellites currently
visible above the horizon to a receiver.
29.Q: What does COG stand for? ANSWER Course Over Ground.
30.Q: What does SOG stand for? ANSWER Speed Over Ground.
31.Q: What does GPS stand for? ANSWER Global Positioning System.
32.Q: Who owns and operates GPS? ANSWER The United States Space
Force (formerly Air Force).
33.Q: When was GPS declared fully operational? ANSWER 1995.
34.Q: What was the original name of GPS? ANSWER NAVSTAR (Navigation
System Using Timing And Ranging).
35.Q: How many satellites make up the baseline GPS constellation?
ANSWER 24.
36.Q: How many orbital planes does GPS have? ANSWER 6.
37.Q: How many satellites are in each GPS orbital plane? ANSWER 4 (with
spares).
38.Q: What is the orbital inclination of GPS satellites? ANSWER 55 degrees.
39.Q: What is the exact orbital altitude of GPS satellites? ANSWER 20,200
km.
40.Q: What is the orbital period of GPS satellites? ANSWER Approximately
11 hours, 58 minutes (half a sidereal day).
