Calibrating a receiver for a satellite positioning system. At preset intervals, a plurality of calibration signals are generated and applied to the receiver. The plurality of calibration signals correspond to a plurality of satellite signals, respectively, from the satellite positioning system. A relative time-delay bias from a delay estimation algorithm within the receiver. The time-delay bias is stored, preferably with the receiver. The receiver receives the plurality of satellite signals from the satellite positioning system. The plurality of satellite signals are processed with the time-delay bias. The processing reduces effects from the satellite receiver and improving estimate of the differential delay and total electron content (TEC).