Start with a high-level overview of GPS as a trilateration system, then dive into signal propagation and error sources, emphasizing the clock mismatch and how it's corrected. Use a structured, layered explanation that connects technical details to practical implications, showing you can handle ambiguity and trade-offs.
Pro tip: Acknowledge that GPS is a system design problem with inherent trade-offs (e.g., accuracy vs. cost), and mention that consumer devices use clever statistical methods to compensate for cheap clocks—this shows you think beyond textbook answers.
Explain that GPS uses a constellation of satellites broadcasting time signals; a receiver trilaterates its position by measuring signal travel times from at least four satellites.
Describe how signals travel at the speed of light, are encoded with satellite position and time, and are subject to delays (e.g., ionospheric, tropospheric) and multipath effects.
Highlight that satellite atomic clocks are highly accurate but consumer clocks are not; the receiver solves for its clock bias as an unknown, requiring a fourth satellite. Other errors include ephemeris, relativistic effects, and atmospheric delays.
Discuss techniques like differential GPS, Kalman filtering, and assisted GPS that mitigate errors, and the trade-offs between accuracy, cost, and power consumption in consumer devices.
Relate to software engineering: how location-based services handle uncertainty, and the importance of robust algorithms to handle noisy data.
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