GPS from getting started to giving up (12), Doppler constant speed

One 、 Doppler effect

Doppler effect There are many in our daily life , For example, when an ambulance comes face-to-face , Hear the sound higher than before ; When the car left, the pitch of the sound was lower than before . This effect is in memory of Austrian physicist and mathematician Christian · John · Doppler （Christian Johann Doppler） And named , He is in 1842 This theory was first put forward in . It is said that once a train passed by him , He found that the whistle went off as the train approached from far away , Pitch sharpening , When the train goes from near to far, the whistle becomes weaker , The tone goes low . He thought it was very interesting , So he studied this phenomenon deeply , The Doppler effect is proposed .

        The main content of Doppler effect is that the wavelength of object radiation changes due to the relative motion of wave source and observer . In front of the moving wave source , The wave is compressed , The wavelength becomes shorter , The frequency becomes higher （ blue shift blue shift）; Behind the moving wave source , Will have the opposite effect . The wavelength becomes longer , The frequency becomes lower （ Redshift red shift）; The higher the speed of the wave source , The greater the effect . According to Bo Hong （ blue ） The degree of displacement , The velocity of the wave source moving in the observation direction can be calculated .

Two 、 Doppler effect in satellite navigation

Doppler effect is not only applicable to sound waves , It also applies to all types of waves . In satellite navigation, radio waves are used to transmit information , Because the satellite is moving around the earth at high speed , So there is also Doppler effect .
 

3、 ... and 、 Doppler constant velocity

This set of constant speed equations can be solved by the least square method . The result is the speed and clock drift of the receiver .