7.1 General requirements
7.2 GPS receiver/decoder
7.3 Unique identifier
The principal concern regarding the physical characteristics for VLD equipment is that it be reliable and present no obvious weakness that could be exploited by an unscrupulous vessel operator.
Equipment must be sufficiently compact to be easily fitted in a vessel wheelhouse. It must be specifically designed for continuous, reliable marine use and therefore highly resistant to malfunction caused by vibration, physical shock, electrical surge, changes in temperature, moisture and humidity and corrosion. Certification of this resistance needs to be certified either by a competent authority designated by the VMS operator or one of the recognized, international certification services, such as Lloyds, Bureau Veritas, Det Norske Veritas, etc. The standard components (antenna, communications unit and input device) must be securely mounted to the superstructure of the vessel with marine grade components supplied with the units.
When the positioning function is assured by a GPS decoder/receiver that apparatus must be an integrated part of the VLD rather than an external unit. Furthermore, it is essential that the VLD and GPS share a single, integrated antenna.
In order to meet the requirements for system security and integrity, it is essential that each VLD carry a unique and unmodifiable identifier that is delivered with every message that it sends. This issue is discussed in a more detailed manner in section 9, Security.
That a VLD be properly installed aboard a vessel is a pre-condition for its qualification for use in a VMS scheme. This means that it be capable of continuous, reliable operation. This requires that the fixtures used in the installation be capable of securing the unit so as to neutralize vibration and shaking and that the antenna be installed in a place where it has continuous, unobstructed view of the satellite.
Furthermore, the antenna site must be suitably distant from antennas of other communications systems, navigation antennas or magnetic compass. The antenna cable, must be installed in such a way as to avoid interference with normal ship activity or to be protected by a reinforced conduit if this is impossible.
Finally, the use of an auxiliary power supply is recommended as is the use of waterproof connectors for both antenna and power connections.