Short answer
A precise GNSS positioning technique using globally-broadcast precise orbit, clock, and atmospheric corrections to deliver decimetre-to-centimetre accuracy with a single receiver — no local base station required. Convergence times of 10–60 minutes for cm-level; instant for decimetre via PPP-RTK.
Detailed explanation
Classic PPP processes dual-frequency carrier-phase measurements from a single receiver, using precise satellite orbit and clock products (IGS, EPOS, or commercial services like TerraStar, OmniSTAR, NTRIP-PPP) broadcast via geostationary satellite or internet. The receiver corrects each measurement using the global products, models ionosphere and troposphere, and converges to centimetre-level over 10–60 minutes of continuous tracking.
PPP-RTK (also called precise PPP, SSR-PPP) adds locally-derived atmospheric corrections from a regional reference network to compress convergence into seconds. This bridges PPP and RTK: you get centimetre accuracy with no local base radio (like PPP) but with the instant convergence of RTK (like RTK). Examples: BDS PPP-B2b, Galileo HAS, Trimble RTX, NovAtel TerraStar-X.
PPP convergence depends heavily on receiver location, sky visibility, ionospheric activity, and signal continuity. A rooftop receiver under quiet ionosphere can fix to 10 cm in ~15 minutes; an obstructed receiver under storm-time ionosphere may need an hour or never fully converge.
PPP works with any high-quality multi-frequency GNSS antenna — phase-centre stability is critical because there's no local base to differentiate out the antenna error. GNSource survey-grade antennas (CA341 choke ring, multi-band helices) are sized for PPP-grade precision over hours of unattended operation.
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High-Precision GNSS Measurement
Browse product lineRelated terms
RTK
A differential GNSS technique using carrier-phase measurements from a known base station to give a moving rover centimetre-level (typically 1–3 cm) horizontal accuracy in real time. The dominant high-precision GNSS technique for cadastral surveying, machine control, and precision agriculture.
CORS
A permanently-installed GNSS receiver streaming raw measurements 24/7. CORS networks are the backbone of RTK and network-RTK services, geodetic monitoring, and post-processed precise positioning. Typical inter-station spacing is 50–100 km for regional RTK, 200–300 km for national geodetic networks.
Phase center
The apparent electrical centre of an antenna — the point from which signal range is effectively measured by a GNSS receiver. Phase-centre stability (the variation in this point as the signal arrival angle changes) is the single most important parameter for survey-grade and geodetic antennas.
BeiDou
Chinese GNSS, fully operational with BDS-3 since 2020. Broadcasts global civilian signals on B1I/B1C (1561 / 1575.42 MHz), B2a/B2b (1176.45 / 1207.14 MHz), and B3I (1268.52 MHz), plus the unique BDS RDSS short-message service.