Precise Point Positioning (PPP) is a sophisticated technique used in satellite-based positioning systems, such as GNSS, to determine a single location with high accuracy, with the help of Global Network of Reference Stations.

Global Network of Reference Stations:
While PPP doesn't require a local base station as RTK does, it benefits from a global network of permanent reference stations. These stations continuously observe satellite signals and contribute to the generation of precise satellite products.

Precise Satellite Products:
Data from the network of reference stations is used to generate precise satellite orbit and clock corrections. These corrections are crucial for PPP's high accuracy. Along with orbit and clock data, other parameters like satellite antenna phase center offsets and variations, and Earth rotation parameters might be provided.

User Receiver (PPP Rover):
The user's PPP-enabled receiver obtains satellite signals like any standard GNSS receiver. Simultaneously, it retrieves the precise satellite products, either by downloading them from a data service (in near-real-time or post-processing applications) or receiving them through satellite broadcasts (real-time PPP).

Correction Application:
The user's receiver applies the precise satellite corrections to the raw satellite measurements it's taking. By doing so, it compensates for the satellite orbit and clock errors, which are significant error sources in GNSS positioning. Additionally, advanced models within the PPP algorithms help correct for other errors, such as those from the ionosphere and troposphere.

Positioning:
With the corrected measurements, the PPP solution can compute a position with high accuracy. However, achieving the highest levels of accuracy with PPP can take a longer time (often called "convergence time") compared to differential methods like RTK.