RTK GNSS Receivers for Centimetre-Level Positioning

RTK (Real-Time Kinematics) is a GNSS technique that uses carrier-phase measurements and real-time differential corrections from a base station to achieve centimetre-level positioning accuracy. Unlike code-based GNSS that measures signal travel time, RTK resolves the integer number of carrier-wave cycles (ambiguity resolution) between the satellite and receiver, eliminating atmospheric and orbital errors shared between the base station and rover.

A fixed RTK solution typically achieves 0.6–2 cm horizontal accuracy and 1–3 cm vertical accuracy. This represents a 100× improvement over standard single-frequency GPS (2–5 m). Eview’s RTK receivers powered by Septentrio mosaic technology achieve 0.6 cm horizontal RMS accuracy. Accuracy can degrade under severe multipath, poor satellite geometry (low PDOP), or during RTK float conditions before integer ambiguities are resolved.

RTK float means the receiver is applying differential corrections but has not yet resolved the integer carrier-phase ambiguities. Float accuracy is typically 0.1–0.5 m. RTK fixed means the ambiguities have been successfully resolved as integers, delivering the full centimetre-level accuracy (0.6–2 cm). The transition from float to fixed typically takes 5–30 seconds with a good GNSS constellation view. A fixed solution is required for all professional survey and precision agriculture applications.

Yes. Network RTK eliminates the need for a local base station by connecting the rover via mobile internet (4G/5G) to a Continuously Operating Reference Station (CORS) network or Virtual Reference Station (VRS) service. Providers include NTRIP-compatible CORS networks operated by national mapping agencies, commercial services like Trimble RTX, or private correction services. This approach is cost-effective and provides centimetre accuracy anywhere within the network coverage area.

Modern RTK receivers like the Eview HB51 and HB52 support all five major GNSS constellations: GPS (US), GLONASS (Russia), Galileo (EU), BeiDou (China), and QZSS (Japan). Multi-constellation RTK dramatically improves ambiguity resolution time and reliability because more satellite observations reduce the time needed to fix integer ambiguities — especially important in challenging environments such as urban areas, tree canopy, or construction sites with partial sky obstruction.

With a modern multi-constellation, multi-frequency RTK receiver under open sky, a fixed solution is typically achieved in 5–15 seconds. Older single-frequency receivers may take 1–5 minutes. Factors that extend initialisation include poor satellite geometry, high multipath, long baseline to the base station (>20 km), or ionospheric disturbances. Eview receivers use GNSS+ algorithms that maintain fixed solutions even after brief signal interruptions, minimising productivity loss during re-initialisation.

NTRIP (Networked Transport of RTCM via Internet Protocol) is the standard protocol for streaming RTK corrections over the internet. Instead of setting up a local base station, the rover connects to an NTRIP caster (server) that distributes corrections from a reference station network. This enables RTK positioning anywhere with mobile data coverage. NTRIP is supported by all Eview receivers and is the preferred correction delivery method for wide-area precision applications.

RTK performance degrades in challenging environments due to satellite signal blockage and multipath reflections from buildings or vegetation. Multi-constellation receivers with 5+ satellite systems track more satellites at lower elevations, improving coverage. Eview receivers include advanced multipath mitigation and RAIM algorithms that reject reflected signals. For severely obstructed environments, RTK can be combined with inertial navigation (IMU) to bridge GNSS outages and maintain centimetre accuracy through tunnels, under bridges, and in warehouses.

RTK (Real-Time Kinematics) relies on differential corrections from a nearby base station or CORS network and achieves 1–2 cm accuracy within seconds. PPP (Precise Point Positioning) uses corrections from global satellite clock and orbit models transmitted by satellite or internet, requiring no local base station but taking 20–40 minutes to converge to 5–10 cm accuracy. PPP-RTK combines both approaches, achieving centimetre accuracy with 1–5 minute convergence anywhere globally — ideal for offshore, remote, or airborne applications where no local reference network exists.

RTK positioning is the standard for land surveying and cadastral mapping (sub-cm boundary accuracy), construction (machine control, grade management, layout stakeout), precision agriculture (sub-row autonomous guidance, yield mapping), UAV photogrammetry (GCP-free centimetre orthomosaics), mining (volume measurement, blast pattern layout), railway and road infrastructure (alignment surveys), and port and marine operations (berthing assist, dredging control). Any application requiring repeatable accuracy better than 5 cm relies on RTK GNSS technology.