Doppler Navigation system

1.Doppler navigation is a self-contained dead reckoning system i.e. it required no external inputs or reference from ground stations .

2.Ground speed and drift can be determined using a fundamental scientific principle called doppler shift.

3.Doppler navigation system were developed in the mid 1940 and introduce in the mid 1950 as a primary navigation system with many features including continuous calculation of ground speed and drift being self contain the system can be used for long distance navigation over oceans and undeveloped areas of the globe  .

4.Doppler sensors are used in other specialised airborne applications, including  Weather radar and missile warning system. and has VOR ground installation also incorporate doppler principle .

5.The doppler effect is name after christian doppler  (1803-1853)  An austrian mathematician and physicist. his hypothesis was that the frequency of a wave apparently changes as it source moves closer to, for further away from, an observe

Fig. Doppler shift principle is also used in speed gun to know the speed of the vehicle.

To illustrate this principle consider an observer located at a certain distance from a sound source that is  emitting a fixed frequency tone. As the ambulance approaches the observer,  The number of cycles received by the observer is the fix tone plus the additional  Cycles received as the function of the ambulance speed. This will have the effect of increasing the tone, (above the fixed frequency)  as heard by the observer. At the instant when the ambulance is adjacent to the observer ,the to true fixed frequency will be heard . When the ambulence travels away from the observer, fever cycles per second will be received and the tone will be    below the fixed frequency as heard by the observer  .The difference in tone is known as the doppler shift

Operations:

If  the signal is sent forward from an aircraft in flight, the returning signal will be at a higher frequency than the signal emitted. The difference in the frequencies makes it possible to measure speed and direction of movement of the aircraft, thus providing information which can be computed to give the exact position of the aircraft at all times with respect to a particular reference point and the selected course.