Abstract: The present invention describes a method and a system to compute the time (t1) and the position (P1) of a receiver (102, 805, 901) based on satellite radiofrequency signals without accurate, a priori time or position information and without the need for demodulating data from the signals received by the satellites (103, 800). In particular, the present invention computes the receiver time (t1) and position (P1) by estimating the time offset between the actual time (t1) and an initial time (t0), which can be defined arbitrarily and even have an error of hours or days. The estimation of this time offset is performed by updating Doppler estimations (D(t0), D(t1)) between different times using Doppler change rates.