Which GNSS measurements are involved in tightly coupled integration?

• A. Pseudorange and Doppler
• B. Only Pseudorange
• C. Carrier phase only
• D. Doppler only

Answer: (A)

Tightly coupled GNSS/INS integrates GNSS measurements directly into the estimation filter alongside inertial data, so the measurements chosen must provide direct constraints on both position and velocity. Pseudorange gives the approximate distance from each satellite to the receiver, anchoring the position estimate, while Doppler provides the rate of change of that range, constraining the velocity. Carrier-phase observations can offer higher precision and help with ambiguity resolution, but they introduce phase ambiguities that aren’t required to describe the basic tight integration approach. Therefore, the combination of pseudorange and Doppler best fits what tightly coupled integration relies on.