RTK
Real time kinematic positioning (RTK) is a technique used for enhancing the accuracy of positional data from GPS's. Essentially, RTK works by comparing the phase of the carrier wave of the signals received from GPS satellites with a reference station that is known to have a precisely known location. This reference station is typically a fixed, known location with a high-precision GPS receiver. The difference between the phase of the carrier wave at the reference station and the phase observed by the mobile receiver is used to calculate very precise position information. By using this correction data from the reference station in real-time, the mobile receiver can achieve centimeter-level accuracy in its position determination.
Please watch these videos to gain a deeper understanding of RTK and how GPS's work
RTCM messages contain pseudorange correction data for GPS satellites. This is the data we want to transmit from the base station GPS to the rover GPS. We currently have a node that publishes the RTCM's from the base station GPS to ROS. We are currently working on implementing our own gps driver that would read the RTCM's from ROS and then send them to the rover GPS. The current branch where we are developing this code on is linked here