Patent ID: 7109920

Claim:
A method for determining a position of a moving platform, the method comprising: transmitting a carrier signal from one of the moving platform and a stationary platform; receiving a received signal at the other of the moving and stationary platforms; deriving a frequency shift between the carrier signal and the received signal; and calculating the apparent closing velocity using the frequency shift and a frequency of the carrier signal; wherein calculating the apparent closing velocity comprises using the equation: f d ⁡ ( t ) = f c ⁢ v c ⁡ ( t ) c + f m + n ⁡ ( t ) wherein fd(t) represents the frequency shift, fc represents a center frequency of the carrier signal, c represents a speed of radio propagation, fm is a constant frequency offset between local oscillators at the transmitter and the receiver system, n(t) represents a measurement noise and vc(t) represents the apparent closing velocity.