Navigation

Most dinghy cruisers sail within harbours and estuaries or within half a mile or so from the shore so do not need to plot a course on a chart or fix a position with multiple compass bearings, even if these were practical things to do on a small open boat. Most dinghy navigation is based on observation of ones surroundings and is perhaps better described as pilotage rather than navigation. For example you find that it quite often helps to be on the windward side of a river, then if the river turns towards the wind you may escape having to put in a tack, also if you run aground it will be easier to get free. You learn that when you turn a corner into a tributary creek you may hit a spit of mud that has formed where the water flows merge. A book which includes a lot of hints and amusing anecdotes relevant to this kind of navigation is 'Sailing Just for Fun' by Charles Stock. Over several decades Charles has covered many tens of thousands of miles of sailing mostly on the coastline of Essex, Suffolk and Kent, which is home waters for the HSC. Anyone who has done any amount of sailing in this area is likely to have come accross Charles Stock with his engineless green painted gaff rigged sloop which has a hull about the size of a Wayfarer, although it is a completely different kind of boat being much heavier and having a cabin. I believe that some years Charles has been out sailing in this boat every weekend, winter and summer. It is unlikely that anyone else alive would know these waters as well as he does. I can recall one Charles Stock anecdote myself. A few years ago Josephine and myself were crew members on a hired cruising yacht proceeding under power up the River Thurne in Norfolk under the command of a rather bossy female skipper. We were sitting on the foredeck to keep as far as possible from the yacht's command centre. As we rounded a bend we spotted Charles Stock in his little green boat tacking up the river ahead of us, so we waved to him but he did not seem to recognise us. Our yacht carried on under power then when we were right up to him we slowed down and followed breathing down his neck so to speak. I could see that Charles was getting quite annoyed because we were neither speeding up to pass him nor slowing down to fall back and give him space to tack freely. Our skipper was getting impatient too, and eventually she opened the throttle wide and went for it as Ellen MacArthur would say. We would have got past safely but then Charles tacked and our skipper panicked and put the engine astern again. A collision was imminent but Charles managed to avoid it by immediately tacking again, but now he had lost steerage way and his boat went straight into the reed beds along the river bank. Our engine gunned again and off we went up the river, leaving Charles stuck in the reeds and shouting something not very polite about people who hire sailing boats then drive them around under power. Josephine and myself were no longer waving but rather trying to duck down out of sight.

Although dinghy navigation is something you will mainly learn by doing rather than by reading there are a just a few things that you really should know before you go afloat in any boat, on saltwater at least. These include the rules of the road (ie who has right of way when boats are on a collision course), the basic IALA system of navigation marks and, in case you get caught out after dark, the basic lights shown by different vessels. These topics are well covered by books available from public libraries and of course plenty of sailing schools, adult education colleges and sailing clubs offer navigation courses following the RYA sylabus. The RYA approved courses cover more than is needed for dinghy cruising but I would not want to discourage anyone from taking such a course, apart from anything else I believe that they can be good social occasions for the winter months. But if you do not have time to take a course do not be discouraged, the essentials require only an hour or so reading.

For the kind of navigation we are discussing here, you don't need any expensive instruments but a small magnetic compass of the type used by hill walkers is so compact and inexpensive that it is worth having one aboard, then you will have some idea of the direction to head back to land if you get lost in fog or just heat haze.

Although some sailors may think this is heresy I would say that I find ordnance survey maps more useful than charts for most coastal and estuary dinghy cruising. Maps show all sorts of interesting and even useful information which is not on charts, e.g. location of pubs, phone boxes, footpaths, lanes and places of interest for exploring ashore. Much dinghy navigation is based on observation of the shore and good maps show details of the shoreline and adjacent landmarks more clearly than most charts. A good map will show tiny creeks and inlets where a dinghy may find shelter, these may not be quite so clear on charts which are produced with larger vessels in mind. Unfortunately maps do not give much information about the depth of water but this is less important for a dinghy than for a keel boat. It is also unfortunate that even large scale ordnance survey maps do not show navigation marks such as buoys but that does not mean that you cannot make use of such marks, the IALA buoyage system is standardised so that you can tell where a channel runs or which side to pass a danger point without needing to identify the marks on a chart. I suppose you really should have a full set of both charts and large scale shore maps but they are expensive and rightly or wrongly it is the charts rather than the maps which I tend to do without, not everyone would agree with this.

I started by making the point that most dinghy cruisers do not venture far from the shore but if you do make a passage out to sea, say across the English Channel, then you definitely do need charts. It is useful to include a chart with a small enough scale to show your whole passage without being unfolded to too huge a size. This will help you to see where you are in relation to your preferred destination point and also alternative destinations you may need to suit changing conditions. Plastic charts such as the Stanford series are excellent for use in an open boat. Water resistant ones, such as those from Imray, are better than normal paper but not nearly as good as plastic. If you only have paper charts consider covering them with clear adhesive film, they will then survive better but will not fold up neatly.

The Global Positioning System

The Global Positioning System has had a big impact on navigation by land, sea, and air. For a price starting at about uk £150 at the time of writing, you can buy a hand held waterproof unit which will reliably tell you your position to within something like 15 metres, or possibly better where various signal enhancements are available. In the context of sailboat navigation that means 'spot on'. A GPS unit usually offers functions additional to the basic position display, for example an accurate speed indication and a 'pointer' which can help you get from A to B a little more quickly by telling you the exact course to steer to counteract a cross current. A gps unit is particularly valuable in fog or darkness or if you sail out of sight of land but I would make the point that we used to manage fine without it, so if you don't want to get involved with this technology or can't afford it that does not mean you cannot go to sea.

I first purchased a GPS unit a little over a year ago. The unit I purchased is the Garmin 76 so my comments are based on this and since I have not used any other gps I cannot give advice on which is the best to buy. From what other people say they all provide the basic functions, so it is probably a matter of how much extra you want to pay for features such as a larger and clearer display (the Garmin 76 has a higher resolution display than the cheapest models), a built in magnetic compass, built in barometer etc. Also you can go for a unit which displays maps/charts, I can see that would be nice but it really puts the cost up a lot, not just for the instrument but also for the map data which you have to buy separately. I think I am right in saying that the basic accuracy is about the same for all models of GPS since this is ultimately dependant on the satellite system. One feature which I think is important for open boat use is that the instrument is fully waterproof but this does not narrow the choice much since most of the current hand held models do claim to be waterproof.

The Garmin 76 is totally waterproof and is thus be useable in conditions when a paper chart would probably be useless. The battery compartment is sealed from the inside of the unit but it is not fully sealed from outside. I think it needs to be that way since otherwise you could seal in water when changing the batteries. I often use rechargeable batteries and I have found that because the battery compartment is not sealed these get rusty when used in the Garmin gps, I don't know how rusty they can get before they don't work. If you use throw away batteries they would probably run down before they have time to rust. I have also had the unit stop operating because of poor contact between the batteries and the contact springs. This was a bit disconcerting the first time it happened but I have found that just rolling the batteries around in their compartment restore operation, I do wonder whether Garmin could do something to improve the reliability of these contacts though.

The Garmin 76 GPS is good ergonomically, the screen is high resolution and as large as you could reasonably expect on a hand held unit and you can operate all the buttons holding it in one hand, using the other hand to sail your boat. Garmin do make smaller GPS units than the 76 but for a marine application miniaturisation is probably less important than an easily read screen and easy to operate buttons. Although the 76 is reckoned to have better battery life than earlier units, if you run it continuously from the internal batteries on an extended cruise you would get through quite a few batteries so I normally switch on the GPS only as and when needed. The disadvantage of this is that you cannot then make use of some of the 'fun' functions such as the trip odometer, the calculation of average speed and the recording of a complete map of your route.

You can switch on a GPS at any time without any setting up in advance and after a wait of perhaps a minute or so you will get your position as a latitude and longitude, (or an alternative coordinate system such as the UK Ordnance Survey grid if you prefer). However, to get the most benefit from a GPS it is worthwhile using waypoints which does require a bit more advance thought. Waypoints are simply reference points which you enter into your gps so that the gps can tell you where you are relative to these points. Once you have waypoints set up the gps can tell you your position either numerically as a bearing and distance from any particular waypoint, or graphically as a map display showing your position together with nearby waypoints, or as a compass display telling you which way to steer to go to a particular waypoint. All this is much more immediately comprehensible information than long numbers representing latitude and longitude which are rather meaningless until you have plotted them on a chart, not an instant operation when steering a dinghy with the other hand! The waypoints you enter will often be points along a route you intend to follow but you can also set waypoints for alternative destinations, for hazards you particularly want to avoid or simply as reference points. It may be worth entering waypoints for the location of the compass rose(s) on your chart then you can read the bearing from this point on your GPS and plot your position relative to the chart compass rose.

If you are entering waypoints into a gps while actually afloat in a dinghy you will probably have to do it by estimating the positions from a paper chart and keying them into the GPS. This is the most tedious part of using a GPS and you need to do it a bit carefully since an error in one digit could send you astray. I certainly find it helps to have a chart with a reasonably spaced latitude and longitude grid  rather than just scales at the edges of the chart. Working from the scales at the edges of a chart is really awkward in an open boat since you will almost certainly need to work with the chart folded. If your chart only has scales at the edges, as is the case with the Stanfords charts I have, then I would recommend that you consider pencilling a grid onto the chart as part of your preparation for going cruising - it is much easier to do this on a large desk than working on the bottom boards of an open boat, I can say that having now done it in both situations.

Apart from keying in coordinates there are at least a couple of other ways to enter a waypoint into a gps. One is to press the 'Mark' button (it may have different names on different makes of GPS) which will cause your current position to become a new waypoint. It is always worth remembering to do this each time you leave a harbour entrance, then you immediately have that harbour entered as a waypoint should you need to go back to it for some reason. Another method to enter waypoints which is available on at least some units is to set the gps to the map display and use an on-screen cursor to set the waypoint position. This method can be used with the Garmin 76 but is really more appropriate to units which are capable of displaying a detailed chart.

Many modern gps units allow you to connect your computer to the gps and, amongst other things, this allows you to use your computer keyboard to type in waypoints prior to setting off cruising, or to back up the waypoint data stored in your gps. To do this you need an appropriate computer program  loaded on your computer and many such programs are available as free downloads from the internet. Some of these programs are amazingly complicated and, for example, allow you to scan paper maps into the computer then download your recent passage from the gps and display the map on screen with your passage superimposed. I had a go at this and I have to admit that I found it rather tedious and soon got fed up with it. If you just want to upload waypoints to your gps and download them to keep a backup I think you will find a simpler program less confusing to use, one such program is called 'Easy GPS' from TopoGrafix and it is freeware.

Modern GPS units usually do a little more than just tell you your position.  The extra functions usually include:

Speed. A GPS unit is also an excellent speedometer (ships log). Remember that it tells you speed relative to the earth and that if there is a tidal flow this is not the same as your speed through the surrounding water. Also note that the speed function of a GPS is not reliable while your course or speed is changing rapidly, so it wont give you a good speed indication while you are tacking or for a few seconds after you have tacked. The Garmin 76 allows the user to set an averaging time for the indicated speed, increasing this will improve the accuracy of the indicated speed when you are settled on a steady course but will also increase the time you have to wait for the speed reading to settle after any change in course or speed.

Speed made good. The Garmin 76 can tell you your speed made good in the direction from your present position to a pre-entered waypoint, generally the waypoint you are currently heading for. Remember that this is not the same information as speed made good to windward as indicated by sophisticated yacht instrument systems. Speed made good to windward would be a nice number to know but unfortunately a standard gps cannot tell you this number since it has no way to know the wind speed and direction. I did make one mildly interesting observation based on the speed made good figure from the gps. I was tacking against the tide down an estuary and I entered a waypoint positioned in the direction of the estuary mouth but a long way away, something like 100 miles distant. I then observed the speed made good to this waypoint as I tacked against the flooding tide, remembering that gps readings are rather meaningless for at least a few seconds after making each tack. It was quite clear that my speed was rising by about half a knot each time I headed into the shallow water at the edge of the estuary where the tidal flow was slacker and the gps did give me an idea of just how close I needed to sail to the shore to keep out of the worst of the foul tide.

Estimated time of arrival. I think that most modern gps units will give you an estimated time of arrival, based on the waypoint you have specified for the end of your passage and how fast you have been sailing since you left the waypoint you specified for the start of your passage. This is quite useful as long as you remember that it depends on your speed being consistent throughout the passage. For example, if the first part of your passage has been down tide and you know that the tide is going to turn against you need to make an appropriate, possibly large, correction to the ETA displayed by your gps. I do wonder just how the algorithm for estimating the ETA works. On one occasion we were making a fairly long passage at a steady speed and the gps was displaying a fail constant ETA, as one would expect. We then made a 360 degree turn to avoid another boat and that (perhaps justifiably) caused the gps to loose a lot of faith in our ability to steer a steady course with the result that it set back our ETA by what seemed like a rather disproportionate amount!

Tides The Garmin 76 has a function to display the state of the tide at your particular instantaneous position.  Although one can always estimate this information from tide tables it would be really nice to have the information available just by pressing a button. Unfortunately this function is disabled while you are in UK waters. Why is that? Apparently it is because the UK Hydrographic office claim copyright for UK tidal data and will not allow Garmin to program its gps units to display tide times for UK waters, hence uk taxpayers who fund the Hydrographic office will have to continue to work out tide times from soggy paper tide tables!

Clock. A GPS can display the time (usually as Greenwich Mean Time). The time displayed is based on data from one of the most accurate clocks ever made so you can certainly depend on it to set your watch.

Looking to the future, one can well imagine that GPS units with built in maps will improve and will become more affordable. It is likely that at some time, perhaps not far in the future, a hand held gps unit with a high clarity color display will become a viable replacement for paper charts and maps. This would be even more significant to open boat cruising than to yacht cruising since paper charts are more difficult to use on an open boat than on a yacht's chart table. It is not hard to imagine that an advanced gps unit could not only display a map but could also act as a pilot book giving textual and photographic information about harbours and other travel information such as bus and train timetables.

I did look at a couple of map equipped hand held gps units at a boat show and studied the map displays for the area of Essex which I know well. Based on these particular units, which may or may not have been equipped with the best available map data, I don't think that this technology is yet a substitute for detailed charts or ordnance survey maps. If say, you were sailing a yacht across the Thames estuary from Ramsgate to Burnham on Crouch the gps map of the whole Thames estuary would be quite adequate to guide you into the Whitaker channel and the entrance to the Crouch and the map on the gps would give you an immediate indication of your position relative to any nearby hazards such as sandbanks. If on the other hand you were exploring the Crouch and its tributary creeks in a sailing dinghy the map displayed on the gps would not help you much. For example, on the gps unit I looked at, the small creeks around Potton Island were shown all merged into one large lake.

If you do make long passages, say across the wide end of the English Channel, I think you will find GPS to be particularly useful. Indeed it works so well that it almost spoils the fun, it used to be quite interesting to find out how accurately, or inaccurately, you could find the way with just chart and compass. I even once had the excitement of landing on a foreign shore not knowing for certain where I was to within something like 20 or 30 miles either way, one could almost imagine being a real explorer. With GPS all that is in the past, navigation is no longer a matter of finding out where you are, it is simply a matter of deciding where you would like to go.