Conventional VOS observations are sent ashore through different way.
The most traditional way consists in sending a FM13 SHIP message ashore through the Inmarsat GMDSS terminal of the ship. This terminal is mandatory on all ships over a certain tonnage. The communication is paid by the meteorological centre that receive the data. Short Access Code (SAC) 41 may be used.
Two other use of GMDSS terminals exists: for AMVER SEAS messages (NOAA) and for E-SURFMAR half compression messages. SEAS messages require the terminal is put in Data Mode whilst E-SURFMAR messages look like BinHex characters. In both case, observation data are binary (i.e. compressed). The conversion to GTS codes (FM13 SHIP and FM94 BUFR) is ensured at the processing centre that receives the raw data. Metadata may be added to observation data there. Communications are also paid by meteorological services. Raw E-SURFMAR dataformat #101 was designed to save communication costs while at the same time being closer to BUFR requirements in matter of accuracy and meeting new requirements for ship data (VOSClim parameters).
More and more observation messages are sent ashore by email at the ship expenses. For the moment, most of them are FM13 SHIP messages.
By mid-2014, several centres receiving FM13 SHIP messages from the ships, convert them into FM94 BUFR without any metadata.
SEAS and E-SURFMAR raw data are converted in FM13 SHIP and FM94 BUFR (information to be checked with regards to SEAS). A few metadata, such as the level of the different main sensors as well as the type of the station are added in BUFR messages to E-SURFMAR observation data prior to their transmission onto the GTS.
BUFR template used for ship data is presently TM308009 (B/C10). It should be replaced by TM308014 (not yet validated) on next year. GTS headers for ship data start with character string 'ISS'.