High-accuracy GPS/GNSS ranging: For obtaining accurate satellite–receiver distance (pseudorange), which measures are used?

Introduction / Context:
Accurate GNSS positioning hinges on precise measurement of the signal travel time from satellite to receiver. Multiple techniques are combined to reduce errors and enhance resolution, especially for surveying, geodesy, and precision navigation.

Given Data / Assumptions:

• Signals include coded ranging and carrier waves.
• Propagation through the ionosphere and troposphere introduces frequency-dependent and neutral delays.
• The receiver can track either code phase or carrier phase (or both).

Concept / Approach:
Code-phase ranging aligns a receiver-generated pseudo-random code with the incoming satellite code to estimate travel time. Atmospheric models or dual-frequency combinations mitigate propagation delays. Carrier-phase tracking measures the phase of the high-frequency carrier for millimetre-level relative precision, resolving ambiguities through differential/RTK/PPP techniques.

Step-by-Step Solution:
Perform code synchronization to obtain an initial pseudorange estimate.Apply ionospheric (e.g., dual-frequency iono-free linear combination) and tropospheric (mapping functions) corrections to refine the travel time.Track carrier phase to reach high precision and fix integer ambiguities with suitable methods (RTK/PPP).Combine these steps to achieve accurate ranges and positions.

Verification / Alternative check:
Differential techniques and PPP solutions demonstrate centimetre-level positioning when atmospheric models and carrier-phase are employed alongside code ranging.

Why Other Options Are Wrong:
Any single measure without the others leaves significant unmitigated error sources.Only code sync: Insufficient for high accuracy because atmospheric and clock errors dominate.

Common Pitfalls:
Ignoring integer ambiguity resolution; neglecting neutral atmosphere delays; assuming single-frequency receivers can reach geodetic accuracy without models.

Final Answer:
All of these.