There is an array of mesmerising chart plotters to tempt you from your cash. Colin Jones gets you clued up on what to look out for...

BUYING a chart plotter is a refreshingly simple exercise because it is a very fair market, in which the more you pay, the more you get. More cash means more navigation power and efficiency. In general terms, you also get more pixels per pound, allied to bigger displays, which are usually worth the extra outlay, especially for the pilotage of fast, open boats. The complexity in your chart plotter purchase stems largely from the fact that there is a choice of cartography (usually C-Map, Garmin or Navionics) and the fact that different plotters have different functions and their own variations on how to activate them. For the newcomer, that often means that you don't know which functions will be the most useful to you, until you have had the CP on your boat for a few weeks.

However, no matter what sort of boat you drive and where you plan to go, there are several criteria common to us all. Firstly, you must really like the CP you buy, because that in itself will encourage you to learn its more advanced features. Also, there is a world of difference between a salesman whizzing around a catalogue of buttons at a boat show and you using the same equipment on a bouncing boat, when your hands are cold and wet or wrapped in glove fabric. The CP's most important surface elements, therefore, are the keys and the display. The keys should be far enough apart to make incorrect pushing less likely and the display must be clear enough to read at a glance in sunlight while moving when your head is at least an arm's length from the unit. Screen quality is obviously a major factor in the price you pay. You need one which is very clear even in bright light, with the sun shining directly onto the glass and it needs to be stable enough not to burn out in heat. Some have a much wider viewing angle than others so if you plan to mount the CP in front of the navigator, you need to make sure that you can get an instant mental picture of the channel ahead when glancing sideways at an angle to the screen.

A fixed CP is generally better than a handheld model in most respects. But a fixed plotter should not be permanently fixed. It must be easy to take off the boat so it can be removed when you pop across the quay for a coffee or go to get the car and trailer. If you have a 12v power supply at home or even an old car battery it also means you can enjoy planning journeys and trying out routes at home. It is a good idea, and a useful tool in becoming accustomed to your CP functions, to record marks of all the local hazards and to mark a safe turning point to enter any harbour you use. If your club deploys fixed racing marks, they can also be permanently plotted. The same goes for your favourite spots for diving, fishing, anchoring or beaching, so you can drive straight to them when you get a day out on the water. At sea, some of the most frustrating moments are when you know that a CP will perform a certain function, but you cannot recall how to do it. Sometimes, the CP will behave like a computer and seem to lock up.

This is rarely the fault of the machine itself and is likely caused by operator error. There is always a way out explained in the user manual but needing to read this mid-channel, or during the Cowes to Torquay Race, is not recommended. The more you use the CP at home, the more effective you will be at sea. Where and what to buy are always the big questions. We all love a bargain and you will find a great spread of opinions at the club bar about where to get the best plotters at fantastically low prices. But these places are often the centre of many financial and morale tragedies. Buying a CP is firstly a task of choosing your cartography. The three major suppliers are all good and are somewhat similar in appearance. The main difference is in their coverage so if your boating regularly occurs in one area, be certain that it is covered by just one cartridge. Electronic cartography is not cheap, so it would be daft to opt for a marque which has a chart dividing line in the centre of your 'playground,' effectively forcing you into a three figure bill instead on one below £100. Some suppliers who are concessionaires of the big three will customise a cartridge to suit your needs. Others offer a rewrite service generally at 50 per cent of the original price which simply overwrites your existing cartridge.

Electronic chart suppliers have the marketing problem that once you have bought the 'map' (or maps) of your area, there is no need to buy anything more, especially if you do your own chart corrections. This is not good for their cash flow, so they are constantly striving to tempt us with add-ons. These need to be looked at with a jaundiced eye. Some of the supposed 3-D functions are so convoluted that I find them next to useless. They are rapidly getting better, but if you are not a diver or a sea angler, it is quite possible that a stand-up graphic of the seabed will be surplus to requirements. A great many of them remain quite crude too so make sure you need and enjoy it before you take the plunge.

Having aerial or satellite photographs of your harbour or estuary is very clever and very tempting but I find that once I have got over the novelty of having them, I rarely bother to look at them and, during my planning, can get just as good a bird's eye view from Google Earth. Again, I would be reluctant to part with extra cash just to add photographs to my existing charts but if you have the money and you are a committed fan of gimmickry you may feel different. There are several ways to buy hardware but the one to be approached with most caution is the internet. I recently traced a line of supply claiming to come from Plymouth but not having an 01752 phone number. It proved to be a couple drop-shipping CPs from America. Unfortunately, some of their models were incompatible with UK cartography and others (from reputable makes) would not qualify for any warranty work in UK, nor for any back-up. Even worse, the packages were labelled 'gift', which makes them non-liable for import duty.

Most of them got through, but Customs opened one package, costing the buyer £135 in dues. He could have bought it cheaper in any UK chandlery and could certainly better the price by examining local adverts and catalogues. The moral is plain. Go to a proper, reputable UK supplier, who will offer the right kit for the UK plus the warranty and back-up you need. One of the best of these is published by Plymouth's SM Group. It is a big compendium of electronics equipment, beautifully illustrated and listing all prices including VAT. To get this publication, which is good read even if you are not immediately planning to buy, email This e-mail address is being protected from spambots. You need JavaScript enabled to view it or call 01752 241000.