This thesis presents the design, implementation, and validation of a robust, open-source approach to Cooperative Intelligent Transport Systems (C-ITS), with special emphasis on integrating Global Navigation Satellite System (GNSS) data from Real Time Kinematics (RTK) receivers. By leveraging hardware such as the ArduSimple RTK2B board in conjunction with the u-blox ZED-F9R module, the system captures high-fidelity positioning information, indispensable for safety-critical and efficiency-driven vehicular applications. The framework centers on the OScar (Open Stack for Car) project, an ongoing C++ implementation of the ETSI C-ITS standards, designed to expedite adoption and reduce costs through open-source distribution. A key focus is the development of a serial data parser for UBX and NMEA protocols, which processes the incoming GNSS messages and encapsulates them into the V2X C-ITS Services such as the Cooperative Awareness Basic Service (CABS) and the Vulnerable Road Users Awareness Basic Service (VBS).