This readme shares the design of RTK GNSS and future integration of the correction measurements to be transmitted over DDS or as a ROS2 service.
Two methods of GNSS correction: Differential GNSS and Real Time Kinematic (RTK). Both methods correct the position through error calculation from a fixed based station. The set of error correction values are transmitted over a network/data link to the Rover to achieve a more accurate solution.
Differences between DGNSS and RTK:
The major difference between DGNSS and RTK methods is the approach used to calculate the error correction terms. DGNSS uses a transmitted code based difference to determine the error terms, which is a mostly logical layer approach; RTK instead leverages the cyclic nature of the carrier wave to determine the errors, which is a more physical layer approach.
"The configuration of Differential GNSS (DGNSS) and RTK systems are similar in that both methods require a base station receiver setup at a known location, a rover receiver that gets corrections from the base station and a communication link between the two receivers. The difference is that RTK (a carrier phase method) is significantly more accurate than DGNSS (a code-based method).
The advantage of DGNSS is that it is useful over a longer baseline (distance between base station and rover receivers) and a DGNSS system is less expensive. The technology required to achieve the higher accuracy of RTK performance makes the cost of a RTK-capable receiver higher than one that is DGNSS-capable only." - Novatel