Transcript
GMDSS and Divers The Global Maritime Distress and Safety System (GMDSS) has been around for a while now so it’s time to revisit and look at the functionality that divers can use from the system. Let’s break it to the component parts that could be useful for us divers: VHF Marine Radio – There’s some features in modern VHF Radios that can be useful to divers if used correctly. 1. Digital Selective Calling (DSC) can be used to call the Coastguard for routine traffic to report start and finish of diving activities for instance. This is particularly useful in busy radio traffic areas and times so you’re not waiting to call in. The radio should be programmed with the Marine Mobile Service Identifier (MMSI) of the local Coastguard that you are reporting to, details of these can be found at: http://www.coastalradio.org.uk/mmsi.htm You’ll need to refer to your VHF manual to learn how to programme these numbers into your radio. I’m also assuming that your vessels MMSI has already been programmed into the Radio, as this information is passed within the digital information sent to the coastguard. 2. Distress Alerting is only used when there is imminent danger to the vessel or the people on board – this can also include missing divers. Your vessels MMSI, position (if the GPS is connected to the radio) and the nature of your problem (if programmed) is sent digitally to all vessels and stations within radio range. Normal voice communication is then established with the coastguard to confirm the problem and the nature of assistance that is required. Using the system like this can save valuable time in the event of an emergency, I’ve noticed that a few club owned dive boats have not wired their radio to the GPS so will not send the full distress message when the red button is pressed. To connect the sets is really easy you just need to connect the NMEA out lead from the GPS to the NMEA in lead on the radio. There’s usually a common earth via the power lead, the GPS will need to be set to the correct output protocol (NMEA), refer to the manual. NMEA is a communication protocol to allow marine electronic devices to exchange information with each other. National Marine Electronics Association is the body that sets the standards for the protocol, hence the acronym. As the data rate is relatively slow many manufacturers have set their own protocols to exchange data within their product range only. However all still support the NMEA protocol as well. 3. Communication Check is not part of GMDSS but common sense. Most branch boats now report to the coastguard their dive plan and estimated return time to their launch position as a matter of routine. This not only communicates your plan but also checks the condition of your radio, antenna and power leads which all have an effect on the transmission range.
Automatic Identification System (AIS) is useful if you have a chart-plotter and you want to see larger vessels within your immediate area. Each vessel over 300tg has to transmit their position, course, speed and other data via a small transmitter using two frequencies within the marine VHF band. You will need a separate receiver to pick up this signal which connects to the chart-plotter (NMEA data again) which then shows the vessels on the chart-plotter screen. You will either need an antenna splitter or a second carefully positioned marine VHF antenna to receive the signals. The reason for this is that when you transmit on you radio the AIS receiver has to be isolated from the signal going out otherwise it could be damaged. Emergency Position Indicating Radio Beacon (EPIRB) can be used on a vessel or as a personal device on a diver to transmit a signal to a satellite that there is a problem that requires the help of the rescue agencies. The satellites are monitored globally and constantly although the satellites are like buses in that there might not be one around when you need it! The distress signal is likely to be received within one hour however. Most of these devices have an integral GPS receiver so that the position of the casualty is relayed to the Coastguard. If the EPIRB doesn’t have an integral GPS the approximate (5km) location can be worked out by the satellite from the signal it receives. Some devices also have a small radio transmitter that a helicopter, aircraft or lifeboat can home in on and finally locate the casualty. Personal Locator Beacon (PLB) has been largely superseded by the introduction of the EPIRB. However there are some still around and they can be used for a helicopter, aircraft or lifeboat to home in on and finally locate the casualty. Electronic Visual Distress Signals (EVDS) also known as electronic flares are not covered by the GMDSS standard. In reality these are only a bright electric flashlight (diver’s torch?), also available is a laser rescue flare, which is visible up to 20 miles away in optimal conditions. All these devices are not effective during daylight hours.
Output of laser flare
These devices are not seen by the Marine Coastguard Agency (MCA) in the U.K. as a suitable replacement for conventional pyrotechnic flares (2013), more information can be obtained from: www.dft.gov.uk/mca/mcga07home/newsandpublications/pressreleases.htm?id=090E6D7DAF9C2E3C&m=6&y=2013 Summary: So, there are some devices that can really help us as divers and boat operators but they all will need setting up to be effective. Some require a licence (VHF) or registration (EPIRB and VHF) to operate and some need battery changes at specified intervals (EPIRB and PLB). I would ask you to all at least to wire your GPS to your Marine VHF Radio if you have these devices as this can make a real difference in an emergency. Secondly think about the position and condition of you VHF antenna as the higher it is the more distance of transmission can be achieved. Integral to this is the power lead, antenna lead and antenna itself. I’ve been on a hired RIB this year where the power lead was faulty and receiving was OK but when trying to transmit the radio powered down - there was corrosion in the power lead! There are tests to establish the effectiveness of a VHF antenna but the use of the equipment and interpretation of the results really needs a specialist. The best you can do is to establish a communication check with the coastguard at the start and end of the day’s activities.
