How is the velocity of an aircraft measured by passive radio systems?

Correct Answer : Option (B) :   Dead reckoning

Explanation : 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.

Correct Answer : Option (A) :   Bearing

Explanation : 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.

Correct Answer : Option (D) :   GDOP

Explanation : 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.