GNSSRTK

GNSS RTK, or GNSS real-time kinematic, is a satellite navigation technique that provides centimeter-level positioning by applying real-time corrections to carrier-phase observations from multiple GNSS constellations. RTK uses measurements from a reference station with a precisely known position to compute corrections that are transmitted to a rover, allowing the rover to resolve the integer ambiguities of carrier-phase measurements and estimate its position with high accuracy in real time. Additional networks of reference stations can be used in network RTK to improve reliability and extend effective baselines.

In operation, a base station (or a network of base stations) logs GNSS data and broadcasts correction data to the rover over radio, cellular, or internet links. The rover applies these corrections to its raw observations, producing a real-time position solution. Common data formats include RTCM messages, with NTRIP being a widely used transport protocol over the internet.

Accuracy and limitations: Under favorable conditions, RTK can achieve horizontal accuracies of about 1–3 cm and vertical accuracies of 2–5 cm, depending on satellite geometry, atmospheric conditions, baseline length, and multipath. The technique requires a relatively clear view of the sky; obstructions, multipath, ionospheric activity, or GNSS outages can degrade performance. Network RTK can mitigate some baselines by using a regional reference network but introduces dependency on communications connectivity.

Applications: RTK is widely used in surveying, construction, precision agriculture, mapping, and autonomous navigation, where fast, precise positioning is essential. Compared with post-processing PPP, RTK provides immediate results in the field but may be more sensitive to local conditions.