A navigation system for a vehicle, comprising: a first navigation module configured to be installed on the vehicle and track a set of satellite signals for determining a first position; and a second navigation module for determining a second position, wherein the second navigation module is configured to be installed on the vehicle such that the first and the second navigation modules (135, 137) are mechanically connected, such that the first position is dependent on the second position, wherein the first and the second navigation modules (135, 137) are communicatively connected to exchange information including at least one of the first and the second positions, and wherein, at an instant of time during an operation of the navigation system and upon loosing at least one satellite signal, the first navigation module receives the second position from the second navigation module and determines the first position based on the second position, wherein the first navigation module determines a first velocity and determines the first position based on the first velocity and the second position, characterised in that: the first navigation module determines a code-phase of a satellite signal, using the first position determined upon receiving the second position, determines a frequency of the satellite signal using the first velocity, and initializes tracking of the satellite signal according to the frequency and the code-phase of the satellite signal, wherein the first navigation module determines the code-phase Φ̂ of the satellite signal according to Φ ^ = 1 c ‖ x k − x ^ A ‖ − b k − b ^ A + A 1 f Dopp + A 0 φ Λ, wherein x̂ A is the first position of first navigation module A, x (k) is a position of a satellite k transmitting the satellite signal, c is the speed of light, b̂ A is a clock bias on the first navigation module A, φ is the phase of the signal carrier, A 0 and A 1 are receiver dependent constants, and b (k) is a bias on the clock of the satellite k, brackets with subscript [] A indicate the modulo operation, and A is a spatial length of a pseudorandom code identifying the satellite k being re-acquired, wherein the first navigation module determines the frequency f̂ of the satellite signal according to f ^ k = v ^ A − v k ⋅ 1 k λ + f 0 1 k = x ^ A − x k ‖ x ^ A − x k ‖ wherein v̂ A is the first velocity of the first navigation module, v (k) is a velocity of the satellite k, and ||.|| denotes a vector norm, and 1 k is a unit vector pointing from the first position x A to the position x (k) of satellite k, and f 0 is a frequency of the satellite signal; wherein the Doppler frequency f Dopp is the difference between a nominal frequency of the received signal and an actual frequency of the received signal. a first navigation module configured to be installed on the vehicle and track a set of satellite signals for determining a first position; and a second navigation module for determining a second position, wherein the second navigation module is configured to be installed on the vehicle such that the first and the second navigation modules (135, 137) are mechanically connected, such that the first position is dependent on the second position, wherein the first and the second navigation modules (135, 137) are communicatively connected to exchange information including at least one of the first and the second positions, and wherein, at an instant of time during an operation of the navigation system and upon loosing at least one satellite signal, the first navigation module receives the second position from the second navigation module and determines the first position based on the second position, wherein the first navigation module determines a first velocity and determines the first position based on the first velocity and the second position, characterised in that: the first navigation module determines a code-phase of a satellite signal, using the first position determined upon receiving the second position, determines a frequency of the satellite signal using the first velocity, and initializes tracking of the satellite signal according to the frequency and the code-phase of the satellite signal, wherein the first navigation module determines the code-phase Φ̂ of the satellite signal according to Φ ^ = 1 c ‖ x k − x ^ A ‖ − b k − b ^ A + A 1 f Dopp + A 0 φ Λ, wherein x̂ A is the first position of first navigation module A, x (k) is a position of a satellite k transmitting the satellite signal, c is the speed of light, b̂ A is a clock bias on the first navigation module A, φ is the phase of the signal carrier, A 0 and A 1 are receiver dependent constants, and b (k) is a bias on the clock of the satellite k, brackets with subscript [] A indicate the modulo operation, and A is a spatial length of a pseudorandom code identifying the satellite k being re-acquired, wherein the first navigation module determines the frequency f̂ of the satellite signal according to f ^ k = v ^ A − v k ⋅ 1 k λ + f 0 1 k = x ^ A − x k ‖ x ^ A − x k ‖ wherein v̂ A is the first velocity of the first navigation module, v (k) is a velocity of the satellite k, and ||.|| denotes a vector norm, and 1 k is a unit vector pointing from the first position x A to the position x (k) of satellite k, and f 0 is a frequency of the satellite signal; wherein the Doppler frequency f Dopp is the difference between a nominal frequency of the received signal and an actual frequency of the received signal.