A receiver (R) for use in a user mobile terminal (U) in a satellite positioning system having a constellation of satellites (S) in which the receiver (R) acquires data from a satellite related to the position of the mobile terminal (U). A MEMS device (M) is incorporated in the receiver (R) and is adapted for detecting the absolute value ({circumflex over (V)}.sub.u) of the speed of the mobile terminal (U) and subsequently providing said value to the receiver (U). Means are provided for computing, by or for the receiver (R), the value corresponding to the vector components (V.sub.ux, V.sub.uy, V.sub.uz) of the speed of the mobile terminal which in turn make possible the Doppler effect related to the users speed is obtained.