The boat radio.
The radio is an ICOM IC-M601, which can be used as a normal VHF set, but is also fully GMDSS capable. The manual can be downloaded from here as a PDF file. If you have broadband access to the internet, the ICOM American website has a streaming video showing how to use a set similar to ours to make a DSC call. Click here to go there.
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The GPS.
The GPS is a Raynav 300, The manual can be downloaded from here as a PDF file. We also have a bridge card, which is a two page summary of the most frequently used functions. Click here to see that.
Using the GPS
As far as possible, you should be able to navigate home without a GPS. Take a note of the bearing from the port entrance to your destination, and remember the reciprocal. Keep a picture of the visual reference points around your home port in mind, so you can get home if the electronic gizmos fail.
However, here are a few useful tips for the use of the GPS.
- Use the steering display to get close to your target waypoint, and the plotter display to find the site when you get there.
- Make sure there are sufficient GPS waypoints at the entrance to the home port so that you can get back if fog comes down (currently waypoint 38 is set on top of the bar at Littlehampton).
- Familiarise yourself with setting and clearing tracks (manual page 38 onwards). If the entry to the home port is hazardous, clear existing tracks before you leave, and start a new one. Set the period between trackpoints to be as short as possible. Leave port using the centre of the safest passage. If a fog comes down while you are away, you can steer home using the plotter display, following your own outward track backwards (the plotter dispay has variable range, so you can zoom in on your outward track as you get closer to hazardous waters).
- Remember to name all useful waypoints. Un-named waypoints will be deleted from time to time. Waypoints at sites which have been verified by diving using this GPS set should have an 'x' character appended on the end.
- If you get a waypoint from one of the 'Dive [coastlinename]' books, check to see if the last figure group in the Lat/Long figures is in seconds, or in decimal fractions of a minute. For example 000.54.48 could be 48 seconds (or 60ths) of a minute west of 000.54.000, or it could be 48 100ths. This will obviously make a difference to where the figures will take you, since our GPS uses decimal fractions of a minute. Old editions of these books had seconds, and new editions have converted to decimal for the last figure group (and the last figure group only) since this is what all GPS units use.
- If you get a waypoint from another diver club or a boat skipper, ask what the datum used was. There are two in common use: WGS84, which most GPS receivers off the shelf (including ours) use, or OSGB, which some dive boat skippers have in their sets (Ian Taylor of Skin Deep's marks for example are OSGB). Off Weymouth, this makes about a 70 metre difference to where the position will be if you enter a waypoint into a set using a different datum system. For an explanation of datums click here, for an example click here.
This is the summary instruction sheet for using the GPS. There should be a laminated version under the cox'n's seat on the boat.
Ref Card Front
Ref Card Back
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