Instead of relying solely on GPS to determine position, the SiRFstarV architecture gathers real-time information from GPS, Galileo, Glonass and Compass (when operational) satellites, multiple radio systems, such as cellular and Wi-Fi(R), and multiple MEMS sensors, like accelerometers, gyros and compasses.
ENGADGET: CSR sharpens indoor and in-car navigation with SiRFstarV, SiRFusion and SiRFprimaII