FROM DIVER Magazine
By Colin Jones - May 1997
Compasses -
GPS -
VHF Radios -
Echo sounders -
Chart Readers -
Suppliers
Before you get too hooked on expensive toys, you should re-examine what an open diving boat really needs. The essentials - electronic compass, video echo sounder, VHF radio and fixed GPS navigator - are all covered in our listings.
Not all GPS units are dive-boat friendly and not all VHF radios are type-approved, or licensable in the UK. So I have stuck to what I know.
The Far East is now a serious GPS contender. Micrologic has cloned the best features of several other makes. The ML250, for instance, comes pre-programmed with basic tide tables for several hundred harbours to the year 2010. At £399, this is hefty value for money.
Garmin has announced a switch from its clever, but sometimes quirky, single-channel multiplexing GPS receiver technology to full 12-channel reception. This accesses the satellites much more quickly and gives a smoother chart-plotter output. Fixed Garmin models with 12 channels will be worth watching out for.
There is a distinct move towards giving all hand-held GPS units a mounting bracket. This is prompted by demand for use with cars and bikes, but also makes them more suitable for boat use, as does the addition of 12v power options.
A less useful marine trend is to give these tiny units the facility to use electronic cartography, in the form of proprietary cartridges. Those I have examined have displays that are much too small for safe and sensible use at sea. My advice is to wait for full-colour LCD chart-plotters to come down in size.
A number of companies now offer Differential GPS options for those who want to get right on top of small wrecks, or at least obtain precision to within 10m. One possibility is DGPS carried on the Classic FM signal. It can be decoded by a 100 black box - the annual licence fee is £150. Marine Electronic Services has the details.
In radio communications there is much talk about GMDSS, a system that uses Channel 70 for an encoded distress signal, including the vessel's position and call sign, after which distress traffic reverts to Channel 16.
For now, divers can ignore all the rumours. GMDSS currently applies only to vessels over 300 tons and HM Coastguard will continue to monitor Channel 16 for the foreseeable future.
The other buzz words of the moment are "computerised charts". A recent count identified 37 companies working on charting software, but very few trying to design a boat computer at a realistic price and guaranteed to stand the pounding. At the moment, the waterproof standard chart-plotter is still the best bet.
There is some argument for using computerised charts for dive planning at home. This can be fun, but the charts range from the excellent to the dreadful and cost £10 and £30 per chart, plus the software at between £200 and £500 and, in some cases, the licence fee.
Other ways of having the fun of planning are to acquire the C-Map chart reader, which converts its CF89 or CF95 cartography to computer format so that you can work out co-ordinates, courses and distances to the wrecks you plan to visit.
I have been planning trips with the versatile Psion 3 palm-held computer, which can be interfaced with a GPS to give a second display, or to transfer waypoints.
This data can be sent to the Psion from a PC's larger screen and keyboard. You will need the Maritek software to do this, but can use this one tool as a complete boat, engine, navigator and dive management system.
AP Philips has sold its marine interests to Leica (which makes the Magnavox GPS) but the UK distributor of AP equipment remains Ampro. There are no changes to the repair and warranty arrangements and the Decca MkIV is still available.
Appeared in DIVER - May 1997
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