Validating PPP-AR Performance in Sparse Infrastructure: A Case Study with Four Reference Stations

High-precision GNSS services typically rely on dense reference networks to model atmospheric delays effectively. However, maintaining such infrastructure is often impractical in vast or developing regions. This study evaluates the feasibility of Precise Point Positioning with Ambiguity Resolution (PPP-AR) using a minimal network configuration consisting of only four Continuously Operating Reference Stations (CORS).

We focus on quantifying the spatial degradation of positioning accuracy as the distance from the reference network increases. By generating corrections from this sparse cluster, we analyze performance metrics including convergence time, fixing rate, and coordinate precision across rovers located at varying baselines from the network centroid.

The results demonstrate a clear correlation between distance and accuracy degradation, specifically highlighting the impact of residual ionospheric and tropospheric errors. Despite this degradation, the study confirms that PPP-AR can maintain reliable centimeter-level positioning well beyond the limits of traditional Network RTK (NRTK). These findings provide empirical guidelines for deploying cost-effective GNSS infrastructure with optimized station density.