Definition
RTK (Real-Time Kinematic) is a positioning technology that achieves centimeter-level accuracy through differential corrections between a reference station and a mobile station. RTK uses known coordinates and observation data from a fixed reference station to calculate satellite observation errors, and distributes correction data to the mobile station via cellular network or radio. The mobile station then corrects its own positioning results accordingly. RTK is a high-precision implementation of real-time positioning and real-time location, related to differential calibration. RTK is suitable for scenarios requiring high accuracy, such as autonomous driving, agricultural machinery, drones, and surveying and mapping.
In cross-border scenarios, RTK needs to consider multi-country reference station networks (such as CORS) and correction data distribution coverage; multi-country single card can ensure RTK terminals receive correction data across borders.
Technical Features and Architecture
The RTK technology architecture includes: Reference Station — a fixed station with known coordinates that observes satellites and calculates errors; Correction Broadcast — broadcasts correction data to the rover stations via NTRIP, radio, etc.; Rover Station — receives satellite signals and correction data to calculate centimeter-level coordinates; Network RTK — receives network correction services like CORS through cellular networks. Combined with positioning , RTK is a high-precision form of real-time positioning ; combined with differential calibration , RTK is a differential real-time application. In cross-border scenarios, network RTK needs to support multi-country CORS access, with RTT latency controllable.
RTK convergence time is usually on the order of seconds to minutes; obstructions, multipath, and other factors can affect accuracy.
Application in IoT and cross-border scenarios
RTK is widely used in: autonomous driving — vehicle and charging station automatic parking and precise docking; agricultural machinery and precision agriculture — centimeter-level positioning for unmanned agricultural machines and precision irrigation; drones — remote ID , aerial surveying, logistics drones' real-time positioning ; surveying and engineering — engineering surveys and topographic mapping. Cross-border autonomous driving tests, cross-border agricultural machinery, and cross-border drone operations may all use RTK, with one card for multiple countries ensuring cross-border RTK correction data reception.
SimtoLink provides stable connections for IoT devices in RTK scenarios, covering 200+ countries and regions, helping with cross-border high-precision positioning applications.
RTK Corrections, Age, and a Fixed Solution
Real-time kinematic positioning uses observations from a base station, or from a network of base stations, to compute the common error in the satellite signals and send corrections to the rover. The rover applies the corrections to its own carrier-phase observations and, after the ambiguities are fixed, obtains a relative position on the order of centimeters. A float solution before the fix is only an estimate in the middle of convergence. The error may still be decimeters to meters. The result must therefore include the solution state: standalone, float, or fixed, and the age of the corrections. Age is the time from when the correction was generated until it is used. As age grows, the error model no longer matches the current observations, and a fixed solution drops back to float or standalone. When corrections are broadcast over cellular, round-trip delay and congestion become age directly.
Cross-border use has to satisfy three things at once. The distance from the rover to the base in use, or the coverage of the network service, is valid. The rover can receive correction data in that country. Both ends use the same coordinate frame. An account on one country's continuously operating reference network cannot be assumed to keep producing a fixed solution in the same frame in the neighboring country. A radio broadcast is not affected by cellular roaming, but range and license are limited. A network broadcast follows the card. After a border crossing, confirm again that the access address, the mount point, and authentication are reachable in the visited country. Multipath beside a vehicle shed, port machinery, or a building can keep the ambiguities from fixing. The receiver may sit on a float solution for a long time and still output coordinates. If the control program reads only latitude and longitude, it will treat an unfixed point as real.
When a Centimeter-Level Result May Enter Control
A result may enter the control loop when the solution state is fixed, the age is under the limit agreed for that job, satellite geometry and signal-to-noise ratio meet the receiver's fix threshold, the coordinate frame matches the frame used for construction or navigation, and the actuator has a strategy to stop safely on loss of lock or a downgrade. Track recording alone may accept a float solution, and should mark the non-fixed intervals on the track. Row alignment on farm machinery, automatic docking, and setting-out for survey should not use a float solution or an expired correction. Before work across a border, confirm the correction service and cellular access in the next country. If needed, open the new data session before the border, so age does not exceed the limit at the moment of crossing. The antenna's lever arm and height must be written into the configuration. Otherwise the fixed solution itself is accurate, and the control point is still off by the installation error.
Driving an Actuator Directly from a Float Solution
A common mistake is to drive steering or a lift as soon as there is a position output. During the float stage the vehicle has already left the working row. Another is that the correction stream breaks during roaming reselection, age exceeds the limit, and the receiver still holds the fixed flag for a short time. A third is that the base-station coordinate frame does not match the map. The fixed solution is centimeter-level relative to the base, and on another coordinate set it is off by meters. Switching between radio and network corrections without a new initialization uses the wrong base coordinates. In a multipath environment the solution fixes and loses lock repeatedly, and the mechanism jitters with it. The control interface should subscribe only to solutions that are fixed and within the age limit. If either condition fails, leave automatic control and keep the time of the last qualified solution. The log should keep the solution state, the age, and the mount point used, so a later review can tell sky blockage, a broken correction, and a wrong frame apart.
The time automatic control was withdrawn, and the time of the last qualified fixed solution before that, are written in the same log entry. A coordinate without those two times does not enter the job record.