4.2 Other "Transponder" System Installations and Trials
Troughout the world, few "Transponder" systems have become
obligatory and quite a number of trials have been undertaken or are underway to
investigate their performances. Examples of applications and tests (Status 1996) are:
Norway (VTS Fedje); UK (Dover Str / DSC; Pilot Watch / Mobile); Sweden (Lake Vänern /
SDMA / GP&C ; Trollhättan; Göteborg); Finland; NL (Pilot's IDS); Germany
(Elbe Tests / DSC ; LOPOS / Mobile; Inland Waterways); South Africa (Cape Area / STDMA)
Panama (PTU / Mobile) etc.. As part of the Poseidon project of the European Union,
demonstrations will take place in Finland, Germany, Greece, Spain and the UK.
5. A Comparison of Competiting Systems
5.1 DSC Radio Transponders
The DSC transponder has been developed on the base of maritime
operational requirements (IALA), mainly for use on ships in VTS areas ("2S").
When interrogated, the transponder can provide basic (but limited) ship data. DSC
equipment is available as part of the GMDSS equipment, but the software has to be
modified. Channel 70 is available for VHF DSC use, but an additional channel is expected
to be necessary.
5.2 STDMA "Transponders"
The STDMA "Transponders" (Self-Organized Time Division
Multiple Access) has been derived from aviation developments. It is an automatic,
braodcast mode transponder giving comprehensive data exchange at high update rates for
ship-to-ship and ship-to- shore applications ("4S"). The STDMA
"Transponder" has a much higher capacity, but at the time being, there are
problems related to frequency allocations and intellectual property rights.
5.3 Mobile Transponders
Mobile transponders are not permanently installed on ships. Instead,
pilots bring them on-board for regional and temporary use. There are as well stand-alone
systems which transmit only the ship's (pilot's) identification and actual (DGPS) position
to the VTC as LAN systems where all logged-in ships (pilots) can be displayed in a VTC
and/or on every logged-in pilot's laptop sea chart.
