Avionics Multiple Choice Questions on “Navigation Equations”.
1. The navigation equations are used by the on-board computer to calculate position velocity and altitude.
a) True
b) False
Answer: a
Clarification: The navigation equations how the sensor outputs are processed in the on-board computer in order ti calculate the position, velocity and attitude of the aircraft. The navigation equations contain instructions and data and are part of the airborne software that also includes moding, display drivers, failure detection and an operating system.
2. Which one of the following is not an input utilized by the aircraft navigation system?
a) Sonar
b) Radio aids
c) Dead reckoning data
d) Celestial measurements
Answer: a
Clarification: The navigation system utilizes three types of sensor information: position data from radio aids, radar and satellites; Dead reckoning data from inertial sensors; Line of sight direction to stars or celestial measurements.
3. What is the angle between the normal to the reference ellipsoid and the equatorial plane at a point called?
a) Geodetic angle
b) Correction factor
c) Geodetic latitude
d) Earth angle
Answer: c
Clarification: Geodetic latitude of a point is the angle between the normal to the reference ellipsoid and the equatorial plane. Geodetic latitude is our usual understanding of map latitude.
4. Which of the following is false with respect to Earth centered inertial coordinate system?
a) Accuracy is 10-5/hr
b) Newton’s laws are not valid
c) Angular coordinates of stars are conventionally tabulated in ECI
d) Used in mechanizing inertial navigators
Answer: b
Clarification: The Earth centered coordinate system has three navigational functions. First, Newton’s laws are valid in any ECI coordinate frame, Second, the angular coordinates of stars are conventionally tabulated in ECI. Third, they are used in mechanizing inertial navigators.
5. Which coordinate system is used in satellite based radio navigation?
a) Earth centered, Earth fixed
b) Earth centered inertial
c) Geodetic spherical coordinates
d) Geodetic wander azimuth
Answer: a
Clarification: Satellite based radio navigation system uses ECEF coordinated to calculate satellite and aircraft position. The origin is at the mass center of the earth and its axis lies along the earth’s spin axis.
6. Geocentric spherical coordinates are used for short range dead reckoning navigation.
a) True
b) False
Answer: a
Clarification: Geocentric coordinates are sometimes mechanized in short range dead reckoning systems using spherical earth approximation. These are the spherical coordinates of the radius vector R.
7. What is the technique of calculating position from measurements of velocity called?
a) Dead reckoning
b) Doppler radar
c) Secondary surveillance
d) Celestial navigation
Answer: a
Clarification: Dead reckoning is the technique of calculating position from the measurements of velocity. It is the means of navigation in the absence of position fixes and consists in calculating the position by extrapolating measured ground speed.
8. The angle of arrival, relative to the airframe, of a radio signal from an external transmitter is called _________
a) Bearing
b) Heading
c) Phase
d) Approach angle
Answer: a
Clarification: The angle of arrival, relative to the airframe, of a radio signal from an external transmitter is called bearing. Bearing is measured by the difference in phase or time of arrival at multiple antennas on the airframe.
9. ________ related ranging errors to the dispersion in measured position?
a) GEOP
b) GDCP
c) GDOP
d) APEG
Answer: c
Clarification: GDOP or Geometric Dilution of Precision relates ranging errors to the dispersion in measured position. If three range measurements are made in the orthogonal direction, the standard deviation in the aircraft’s position error is the same as those of the three range sensors.
10. What is TDOP?
a) Time Dilution of pseudorange
b) Time Dilution of position
c) Time Dilution of pressure
d) Time Distortion of position
Answer: b
Clarification: TDOP is the Time Dilution of position. It is the contribution of clock error to the error in pseudorange.