GPS receiver processing flow: choose the correct sequence from signal capture to final user output.

Introduction / Context:
A GPS receiver must acquire and track satellite signals, decode navigation data, process observations, and present a position/velocity/time (PVT) solution to the user. Understanding this pipeline clarifies where errors and delays may occur and how augmentation like DGPS fits in.

Given Data / Assumptions:

• Stage 2: Detection of the GPS signal (acquisition/tracking).
• Stage 4: Decoding the GPS signal (navigation message).
• Stage 3: Processing in the built-in computer (solution estimation).
• Stage 1: Generation of output to the user (final PVT).

Concept / Approach:
Receivers first detect and lock onto the satellite carrier and code, then decode the navigation message to obtain ephemerides and timing models. Next, they process the pseudorange and, if available, carrier-phase measurements to estimate position/time. Finally, they output the solution to the user interface or data port.

Step-by-Step Solution:
Start with signal detection: 2.Decode navigation data: 4.Compute solution in firmware/software: 3.Provide user output: 1.Therefore, the correct sequence is 2, 4, 3, 1.

Verification / Alternative check:
Receiver ICDs and textbooks outline acquisition → tracking → data demodulation → navigation solution → output, which aligns with this order.

Why Other Options Are Wrong:

• Any sequence that outputs before decoding/processing is illogical.
• Processing cannot precede decoding of necessary ephemerides/time models.

Common Pitfalls:
Confusing acquisition (signal lock) with data decoding; assuming solutions can be computed without valid ephemerides.

Final Answer:
2, 4, 3, 1