Integrated Navigation Systems (INS)
INS - INTEGRATED NAVIGATION SYSTEMS | VERIFIED
QUESTIONS AND ANSWERS - COMPLETE COVERAGE
LATEST 2026/2027
INTEGRATED NAVIGATION SYSTEMS (INS)
1. An inertial navigation system determines position primarily by:
A. Triangulating ranges from external radio beacons
B. Measuring the Doppler shift of satellite signals
C. Comparing terrain elevation against a stored map
D. Double integration of measured acceleration after gravity compensation
Answer: D. Double integration of measured acceleration after gravity
compensation
An INS is self-contained; it integrates specific force once for velocity and
again for position, after removing gravity.
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, Integrated Navigation Systems (INS)
2. The two primary sensor types found in an inertial measurement unit (IMU)
are:
A. GNSS receivers and odometers
B. Magnetometers and barometers
C. Radar altimeters and Doppler radars
D. Accelerometers and gyroscopes
Answer: D. Accelerometers and gyroscopes
A standard IMU contains a triad of accelerometers for specific force and a
triad of gyroscopes for angular rate.
3. An accelerometer at rest on the Earth's surface, with its sensitive axis
pointing vertically up, will measure approximately:
A. −1 g, equal to gravitational acceleration downward
B. A value equal to Earth's rotation rate
C. 0 g, because the device is not moving
D. +1 g (the reaction to gravity)
Answer: D. +1 g (the reaction to gravity)
Accelerometers sense specific force, not gravity itself; at rest the supporting
reaction force produces a reading of about +1 g upward.
4. The quantity actually sensed by an accelerometer is called:
A. Gravitational potential
B. Angular momentum
C. Kinematic acceleration
D. Specific force
Answer: D. Specific force
Specific force is the non-gravitational force per unit mass, i.e. true
acceleration minus gravitational acceleration.
5. In a strapdown INS, the inertial sensors are:
A. Mounted on a gimbaled stabilized platform
B. Rigidly fixed to the vehicle body
C. Isolated from vehicle motion by torque motors
D. Aligned permanently with local north and east
Answer: B. Rigidly fixed to the vehicle body
Strapdown systems attach sensors directly to the body and use computation
to track attitude instead of mechanical gimbals.
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, Integrated Navigation Systems (INS)
6. Which of the following is the main advantage of a strapdown INS over a
gimbaled INS?
A. No need for any attitude computation
B. Sensors experience lower angular rates
C. Lower mechanical complexity, size, and cost
D. Complete immunity to gyro drift
Answer: C. Lower mechanical complexity, size, and cost
Removing gimbals, slip rings, and torque motors reduces size, weight, and
cost; the trade-off is higher computational load and sensor dynamic range.
7. Gimbal lock in a mechanical platform occurs when:
A. The gyros saturate at high angular rates
B. The accelerometers lose their null bias
C. The platform is aligned exactly with true north
D. Two gimbal axes become aligned, losing one rotational degree of
freedom
Answer: D. Two gimbal axes become aligned, losing one rotational
degree of freedom
When two gimbal axes line up, the platform can no longer isolate rotation
about one axis; a fourth redundant gimbal is often used to avoid it.
8. A ring laser gyroscope (RLG) measures rotation using:
A. The precession of a spinning rotor
B. The Sagnac effect on counter-propagating laser beams
C. Changes in magnetic flux through a coil
D. Coriolis force acting on a vibrating mass
Answer: B. The Sagnac effect on counter-propagating laser beams
Rotation shortens the effective path for one beam and lengthens it for the
other, producing a frequency difference proportional to rate.
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, Integrated Navigation Systems (INS)
9. The 'lock-in' phenomenon in ring laser gyros occurs:
A. At very low rotation rates, where the two beams couple and the output
reads zero
B. Only when the gyro temperature exceeds its rated limit
C. At very high rotation rates, where the counter saturates
D. When the laser cavity loses gas pressure
Answer: A. At very low rotation rates, where the two beams couple and
the output reads zero
Backscatter couples the two beam frequencies at low rates; mechanical
dither is the usual cure.
10. Mechanical dither in a ring laser gyro is used to:
A. Reduce the accelerometer scale factor error
B. Align the gyro to true north
C. Keep the gyro operating outside the lock-in region
D. Increase the laser output power
Answer: C. Keep the gyro operating outside the lock-in region
A small sinusoidal oscillation keeps the sensor moving through the dead
band so the net lock-in error averages out.
11. A fiber optic gyroscope (FOG) differs from an RLG mainly because it:
A. Relies on a spinning mechanical rotor
B. Cannot use the Sagnac effect
C. Uses a passive coil of optical fiber rather than a resonant laser cavity
D. Measures linear acceleration instead of rotation
Answer: C. Uses a passive coil of optical fiber rather than a resonant
laser cavity
The FOG is an interferometric Sagnac device with a long fiber coil and
external light source, so it has no lock-in problem.
12. MEMS gyroscopes typically sense angular rate through:
A. Coriolis force on a vibrating proof mass
B. The Sagnac phase shift in an optical fiber
C. Magnetic resonance of nuclei
D. Precession of a high-speed rotor
Answer: A. Coriolis force on a vibrating proof mass
A driven vibrating structure experiences a Coriolis force perpendicular to its
motion when rotated, which is detected capacitively.
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INS - INTEGRATED NAVIGATION SYSTEMS | VERIFIED
QUESTIONS AND ANSWERS - COMPLETE COVERAGE
LATEST 2026/2027
INTEGRATED NAVIGATION SYSTEMS (INS)
1. An inertial navigation system determines position primarily by:
A. Triangulating ranges from external radio beacons
B. Measuring the Doppler shift of satellite signals
C. Comparing terrain elevation against a stored map
D. Double integration of measured acceleration after gravity compensation
Answer: D. Double integration of measured acceleration after gravity
compensation
An INS is self-contained; it integrates specific force once for velocity and
again for position, after removing gravity.
Page 1 of 54
, Integrated Navigation Systems (INS)
2. The two primary sensor types found in an inertial measurement unit (IMU)
are:
A. GNSS receivers and odometers
B. Magnetometers and barometers
C. Radar altimeters and Doppler radars
D. Accelerometers and gyroscopes
Answer: D. Accelerometers and gyroscopes
A standard IMU contains a triad of accelerometers for specific force and a
triad of gyroscopes for angular rate.
3. An accelerometer at rest on the Earth's surface, with its sensitive axis
pointing vertically up, will measure approximately:
A. −1 g, equal to gravitational acceleration downward
B. A value equal to Earth's rotation rate
C. 0 g, because the device is not moving
D. +1 g (the reaction to gravity)
Answer: D. +1 g (the reaction to gravity)
Accelerometers sense specific force, not gravity itself; at rest the supporting
reaction force produces a reading of about +1 g upward.
4. The quantity actually sensed by an accelerometer is called:
A. Gravitational potential
B. Angular momentum
C. Kinematic acceleration
D. Specific force
Answer: D. Specific force
Specific force is the non-gravitational force per unit mass, i.e. true
acceleration minus gravitational acceleration.
5. In a strapdown INS, the inertial sensors are:
A. Mounted on a gimbaled stabilized platform
B. Rigidly fixed to the vehicle body
C. Isolated from vehicle motion by torque motors
D. Aligned permanently with local north and east
Answer: B. Rigidly fixed to the vehicle body
Strapdown systems attach sensors directly to the body and use computation
to track attitude instead of mechanical gimbals.
Page 2 of 54
, Integrated Navigation Systems (INS)
6. Which of the following is the main advantage of a strapdown INS over a
gimbaled INS?
A. No need for any attitude computation
B. Sensors experience lower angular rates
C. Lower mechanical complexity, size, and cost
D. Complete immunity to gyro drift
Answer: C. Lower mechanical complexity, size, and cost
Removing gimbals, slip rings, and torque motors reduces size, weight, and
cost; the trade-off is higher computational load and sensor dynamic range.
7. Gimbal lock in a mechanical platform occurs when:
A. The gyros saturate at high angular rates
B. The accelerometers lose their null bias
C. The platform is aligned exactly with true north
D. Two gimbal axes become aligned, losing one rotational degree of
freedom
Answer: D. Two gimbal axes become aligned, losing one rotational
degree of freedom
When two gimbal axes line up, the platform can no longer isolate rotation
about one axis; a fourth redundant gimbal is often used to avoid it.
8. A ring laser gyroscope (RLG) measures rotation using:
A. The precession of a spinning rotor
B. The Sagnac effect on counter-propagating laser beams
C. Changes in magnetic flux through a coil
D. Coriolis force acting on a vibrating mass
Answer: B. The Sagnac effect on counter-propagating laser beams
Rotation shortens the effective path for one beam and lengthens it for the
other, producing a frequency difference proportional to rate.
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, Integrated Navigation Systems (INS)
9. The 'lock-in' phenomenon in ring laser gyros occurs:
A. At very low rotation rates, where the two beams couple and the output
reads zero
B. Only when the gyro temperature exceeds its rated limit
C. At very high rotation rates, where the counter saturates
D. When the laser cavity loses gas pressure
Answer: A. At very low rotation rates, where the two beams couple and
the output reads zero
Backscatter couples the two beam frequencies at low rates; mechanical
dither is the usual cure.
10. Mechanical dither in a ring laser gyro is used to:
A. Reduce the accelerometer scale factor error
B. Align the gyro to true north
C. Keep the gyro operating outside the lock-in region
D. Increase the laser output power
Answer: C. Keep the gyro operating outside the lock-in region
A small sinusoidal oscillation keeps the sensor moving through the dead
band so the net lock-in error averages out.
11. A fiber optic gyroscope (FOG) differs from an RLG mainly because it:
A. Relies on a spinning mechanical rotor
B. Cannot use the Sagnac effect
C. Uses a passive coil of optical fiber rather than a resonant laser cavity
D. Measures linear acceleration instead of rotation
Answer: C. Uses a passive coil of optical fiber rather than a resonant
laser cavity
The FOG is an interferometric Sagnac device with a long fiber coil and
external light source, so it has no lock-in problem.
12. MEMS gyroscopes typically sense angular rate through:
A. Coriolis force on a vibrating proof mass
B. The Sagnac phase shift in an optical fiber
C. Magnetic resonance of nuclei
D. Precession of a high-speed rotor
Answer: A. Coriolis force on a vibrating proof mass
A driven vibrating structure experiences a Coriolis force perpendicular to its
motion when rotated, which is detected capacitively.
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