RTCM SC-104
RTCM SC-104 (named after the Radio Technical Commission for Maritime Services Special Committee 104), also known simply as "RTCM", is a communication protocol for sending GNSS-related data. It supports recording and sending navigation messages as received by a GNSS receiver as well as additional correction data such as those for differential GPS (DGPS, observation space) and (since version 3.1 Amendment 5) state-space correction.