Define precise point positioning (PPP) in GNSS.

• A. A network-based approach that uses nearby reference stations to compute the receiver position.
• B. A real-time kinematic method using local base stations.
• C. A processing approach that uses precise satellite orbit and clock products to compute receiver position.
• D. A processing approach that uses precise satellite orbit and clock products to compute receiver position without a nearby reference station network.

Answer: (D)

Precise point positioning is a GNSS processing approach that estimates the receiver’s position using precise satellite orbit and clock corrections without relying on a nearby reference-station network. In PPP, you treat the receiver’s position and its clock as unknowns, along with carrier-phase ambiguities, and you bring in external precise products for satellite orbits and clocks (such as IGS data) to remove the main satellite-related errors. You also model atmospheric delays and sensor biases to achieve centimetre-level accuracy globally, given enough observation time. This stands in contrast to network-based methods that depend on a local network of reference stations to provide differential corrections. The hallmark of PPP is solving for the receiver position with global corrections rather than relying on nearby base stations.