The GPS system is a marvel of engineering, with GPS signals being ever-present at any altitude, in any weather, at all times. Despite the signals being incredibly weak, they can still be detected and decoded thanks to clever signal processing techniques. GPS uses spread-spectrum and code-division multiple access tricks to help receivers lock onto the signals. Each GPS satellite emits a unique PRN code, and GPS receivers must acquire a lock on these codes to determine which satellites are in view. This process involves correlating replica PRNs with live data and accounting for Doppler shifts. The acquisition phase is compute-intensive but crucial for GPS positioning.
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