This activity aims to investigate and prove the concepts of novel user segment VHF Data Exchange System (VDES) technologies to enhance key performance figures of positioning e.g. such as accuracy, integrity and security, and complement ongoing VDES investigations to improve APNT capabilities for relevant maritime use cases. This activity will also investigate and analyse the impact of the key system aspects such as synchronisation/timing issues of VDES-R mode (considering both terrestrial and satellite components), devoted to ranging and navigation capabilities. Lastly, the activity will also assess the alternative PNT solutions based on VDE-SAT in combination with VDE-TER services.