GNSS RECEIVER AND OPERATING METHOD

A GNSS receiver (100) receives radio signals (S(SV)) transmitted from an active set of signal sources (SV1, SV2, SV3, SV5) and based thereon produces position/time related data (DPT). The receiver (100) has a tracking channel resource for each signal source (SV1, SV2, SV3, SV5) in the active set, and the tracking channel resources process the radio signals (S(SV)) in parallel with respect to a real-time signal data rate of the signals. The receiver (100) also includes a signal-source database (140), a signal-masking database (150) and a control unit (130). The signal-source database (140) describes the movements of the signal sources (SV1, SV2, SV3, SV4, SV5) over time relative to a given reference frame, and the signal-masking database (150) reflects, for positions (P) within a predefined geographic area, visibility/blockage to the sky with respect to a direct line of sight in terms of spatial sectors (M1(P), M2(P) M3(P)). The control unit (130) derives data describing a current position/time (PTR(t)) and a current velocity vector (VR(t)) for the receiver (100) based on the position/time related data (DPT); and derives an estimated visibility of the signal sources (SV1, SV2, SV3, SV5) in the active set at a second position/time (PTR(t+ t)) representing an expected future position/time for the receiver (100) based on the signal-source and signal-masking databases (140; 150). If at least one signal source (SV1) in the active set is estimated not to be visible at the second position/time (PTR(t+ t)), the control unit (130) initiates a modification of the active set aiming at replacing the at least one non-visible signal source (SV1) with at least one signal source (SV4) which, based on the signal-source and signal-masking databases (140; 150), is estimated to be visible at the second position/time (PTR(t+ t)).