Digital passage planning and electronic navigation

Drawing up a passage plan is not only common sense, it is a legal requirement under SOLAS V regulation 34 which says that, whatever the size of your vessel, you must make a plan before going to sea. In this context, going to sea is defined in Merchant Shipping Notice (MSN) 1837 as proceeding outside categorised or sheltered waters. Areas where the significant wave height cannot be expected to exceed 2.0 metres at any time are considered to be sheltered; anywhere else is not and a passage plan is required.

Your first responsibility as a skipper is to ensure the safety of your crew and boat, and it would be reckless to set off anywhere without at least some basic planning. A short trip from Portsmouth Harbour to Bembridge Marina for lunch might only involve checking the weather forecast and making sure that you will have sufficient height of tide to navigate the tortuous channel into Bembridge. On the other hand, even a simple passage from Weymouth to Torbay would come under the SOLAS regulations and need a much more detailed plan.

Surprisingly, there is no requirement to make a written record of your plan, but you would be hard pressed to prove you had made one if you don’t. Pilotage plans for departure and arrival are a different subject, and are not covered here.

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Today’s electronics

Before the days of GPS, fixing your position at sea required different techniques for different areas. In coastal waters, visual bearings of charted features was the norm. In the relatively few yachts which were suitably fitted, radar ranges could also be used. Offshore, an accurate departure fix was the basis for navigating by dead reckoning until you sighted land again. On ocean passages, you depended on clear skies to find your position using a sextant.

It was all tremendously satisfying – when it worked – but we have moved on and now you know precisely where you are, at any time of the day or night, by merely looking at a screen. Many other aspects of navigation, both in the planning stages and during a passage, have gone the same way. As a result, much of the tedium has been removed, freeing up time and generally making life easier and less stressful. What’s not to like?

First, a note of caution. Although electronic equipment which is designed specifically for marine use is usually reliable and sturdy enough to put up with life in small craft, it does rely on a constant power supply. This will either be from the boat’s batteries or internal rechargeable batteries. Either way, no power means no output. You can cover your bets by having, for instance, several GPS receivers, both fixed and portable, but most laptops, tablets and phones are not water resistant or even splash-proof, nor are they likely to survive being sat on or dropped. Carrying spares would be impracticable and prohibitively expensive.

So, we have to accept that electronic equipment is vulnerable and can fail, and it isn’t sensible to rely solely on electronics to plan and navigate from
A to B.

I hope that what follows will help you decide what you can delegate to the electronics and what you will do (or at least check) either from paper or online sources. I have focussed on the passage plan itself, but there are some notes at the end about executing it – actually getting safely to your destination. For more advice on this, have a look at Your First Channel Crossing (£15.29, Adlard Coles).

Creating the plan

Let’s see what is needed for a passage plan for a trip from Dartmouth to St Helier, Jersey, a distance of some 90 miles – about 16 to 20 hours for a sailing yacht – across busy shipping lanes and with significant tidal streams. You can then decide how this plan could be simplified for shorter, more straightforward passages.

In particular, we will see what can be done using electronics – internet, digital passage planning programmes, chartplotters, laptops and tablets – and what needs to be done, or can be done more effectively, using paper: almanacs, cruising companions, tide tables and paper charts.

If you are concerned about the demise of Admiralty paper charts from about 2026, it seems that paper charts from other suppliers will continue to be available for many years to come.

So, what is involved? First and foremost, you need to gather data – lots of it. Secondly, that data needs to be refined and organised to form a workable passage plan. And thirdly, a record should be made of all your hard work in a format which can be referred to during the passage.

Some aspects of the plan can be completed well in advance but others must be as current as possible. A route can be drawn on a chart weeks ahead, but tidal stream calculations will only be valid when you know your departure time and have the most recent weather forecasts.

Gathering data

SOLAS guidance covers seven topics, and I have listed them in the same order as they appear in SOLAS. For each one we will examine what is required and what can be achieved electronically or on paper. To some extent, this will be a choice which only you can make.

For those of us of a certain age, while fully acknowledging that electronics do make some tasks very much quicker and possibly more accurate, paper tends to be the default preference. Younger skippers may look to electronic methods first then, in the light of experience, decide what can be done better using printed material.

Weather

There are more options for finding a weather forecast than can be listed here. Be sure of one thing: no two forecasts will be the same. Some people will use the one which best justifies their decision to set off; others, perhaps more prudent, will go for the least favourable.

There are basically two types of forecasts: those which are produced entirely by computers and those which are computer generated but modified by human forecasters. It is easy to become hypnotised by the enormous amount of detail on some weather apps – thousands of little arrows showing a precise wind strength and direction – but a forecaster will know that, for instance, a fresh southwesterly wind in the Strait of Dover is quite likely to be a force or two higher than that predicted by a computer.

Around the UK, I think it is hard to beat the forecasts issued by the Met Office, particularly the Inshore Forecasts for areas within 12 miles of the coast. They can cover quite large areas (Rattray Head to Berwick-upon-Tweed embraces over 150 miles of coastline) but considerable experience from professional forecasters will have gone into their compilation. The same applies to the Shipping Forecast areas around the UK and northern Europe.

When planning your passage, study weather maps and long-term forecasts for several days before leaving, then focus on short-term forecasts as your departure day approaches. Establish some no-go limits. These will depend on your boat and crew, but for our trip from the Dart to Jersey most skippers will baulk at Force 5 or above from the south or southeast, while a strong crew might relish Force 6 from the west or north. Remember that most forecasts predict the average wind strength; gusts might put it out of your comfort zone. Of all the myriad forecasts available, don’t forget your own.

If the actual weather looks threatening or doesn’t ‘feel’ right, think again.

Your plan should also include a note of forecasts which are available while on passage. NAVTEX is probably the most reliable source and will be available for the entire passage. You should also be able to receive routine MSI broadcasts by VHF (from the UK, Channel Islands or France) for most of the time. If you carry a radio capable of receiving long wave (LW), you will be able to get Met Office marine forecasts on BBC Radio 4 at stated times during the day.

Unless you have expensive kit on board, weather apps and other online services will not be available when you are outside WiFi/mobile data coverage, ie when more than about 15 miles from shore.

Tides and tidal gates

Tidal predictions are readily available both digitally and on paper, and there is much to be said for downloading one of the many tidal apps. They are generally quick and intuitive to use, and they can make calculating time and height predictions for non-standard ports a doddle. Accuracy may vary, but probably not by much, and a comparison with the Admiralty tide tables will indicate how much confidence you can have in their predictions.

Depending on your activities, precise tidal height predictions may be of passing interest, but if you are navigating with minimal under-keel clearance, you need the most accurate predictions you can get.

However, no predictions are absolutely accurate in practice. Wind and atmospheric pressure can both cause the tide to be higher or lower.

There is no foolproof formula; judgement is required.

Printed tide tables are cheap and readily available (if you have a nautical almanac on board, you will already have them), and it is often useful to be able to run an eye over a printed page to get a feel for the tides for several days or weeks ahead.

Tidal streams can make all the difference to your passage. Ignore them when sailing east/west in the Channel and you can add hours to your trip; going north/south you may end up miles from your intended destination. Again, no predictions can be totally accurate, but the actual stream can easily be seen as you pass navigation buoys or fishing floats.

Similarly, tidal gates need to be negotiated at certain times to avoid undue delays or rough wind-over-tide situations. On the passage to Jersey, you really don’t want to encounter the start of the strong northwest stream for the leg between Guernsey and Jersey.

Paper or electronic?

Most electronic tide apps are clear and intuitive, and will usually include extras such as sunrise/set, moonrise/set and tidal coefficients. Their accuracy can be compared with a trusted source like the Admiralty tide tables, and you can then judge if they meet your needs. On the other hand, paper tide tables are often reproductions of UKHO’s products.

For tidal streams, an electronic version allows you to scroll through at hourly intervals with a few taps on the screen. The diagrams in the almanacs tend to be very small scale, and the Admiralty tidal stream atlases, although at much larger scales, are expensive and you need several of them. For our passage you would need at least three: NP263 (and/or NP254), NP250 and NP264.

Limitations of the vessel

SOLAS requires you to take the capabilities of your boat into account, but it is a subjective judgement. Although most boats are categorised from A (Ocean passages) to D (Sheltered waters), a private yacht is not bound by her categorisation. If you wish to sail across the English Channel in a 12-foot dinghy, that is entirely up to you.

Recommended lists of equipment can be found online and in the Safety chapter of Reeds. The only gear which you must carry (another SOLAS requirement) are a radar reflector, if practicable, and an illustrated table describing the life-saving signals (again, in Reeds or online).

Also check that you have got sufficient fuel, water and food on board, and that the boat has no defects which could jeopardise safety.

Crew

There are no rules about the quantity or quality of your crew. You are free to sail with whoever you wish, or even by yourself (but check insurance requirements). However, you would have a hard job to convince an inquiry into an incident at sea if you set off without considering the strength and experience of your crew. Remember that it might be you who falls overboard, has an accident or becomes ill, so someone else must be able to take charge and know how to call for help or get the boat to a safe port.

For our passage to Jersey, the skipper should have the knowledge and experience of an RYA Coastal Skipper, and at least one of the crew should be a Day Skipper or equivalent. As you may be sailing at night on this passage, a crew of two may find it rather more than they can cope with. So a third hand might be wise. Whatever your decision, be prepared to justify it if things go badly wrong.

Navigational dangers and Route

We now get to the essence of passage planning. Fine weather, a sound boat and a competent crew count for nothing if you don’t know how to get to your destination. Actions include, but are not limited to:

Many planning programmes will draw a route for you. Just enter your departure and arrival points, and the programme will do the rest. It might also use tidal stream predictions to give you courses to steer to maintain the track, or it will calculate the overall course to steer, allowing for the boat being set off-track one way then the other.

This will be the shortest distance through the water, and will therefore get you to your destination in the shortest time. Most chartplotters and phone apps, however, do not have this functionality, so will result in you hugging the rhumb line, rather than steering the shortest course through the water.

Depending on the criteria you enter (draught, expected speed etc), the track should keep you clear of dangers, but it won’t make subjective judgements.

It might think that a clearance of less than half a mile west of the rocks off Les Hanois and Corbière is sufficient, but I would at least double that – and more in a fresh westerly wind. Consequently, you may need to modify the route by entering some waypoints yourself.

The automatic route calculated by one well-known chart app for a passage from northeast of Guernsey to Grève de Lecq on the north coast of Jersey takes you through some extraordinarily tight passages which would severely challenge even the most experienced local Channel Island yachtsmen. It may be the shortest route but it is certainly not recommended.

The lesson here is to look very carefully at the suggested route and be prepared to amend it manually to reflect sensible navigational practice. As a first stab at time and distance, the automatic function can be useful, but creating a manual route by placing waypoints where you want them could turn out to be a quicker and safer option.

Electronic Charts

There are two types of electronic chart – raster and vector. The former is simply a copy of the paper chart, and zooming in just magnifies the image. Vector charts are made up of layers of information, and you need to zoom in for more detail. There have been many strandings because hazards didn’t show up on the scales which were used during the planning process. If your programme uses vector charts, it is essential that you inspect the track at a large (zoomed in) scale to be sure that nothing is overlooked. At least one app I know doesn’t even show TSSs until you zoom in sufficiently.

The chart is an excellent place to record and show information such as where on the passage you expect to sight land and lights based on the actual visibility and charted elevations; the times of sunset and sunrise; busy shipping lanes; overfalls where you might expect particularly uncomfortable seas; and the times of turning points. In our example, turning points would be off the southwest tip of Guernsey and off Corbière on Jersey. All this will help you to decide who you need on deck at critical points, and when you can sensibly get a bit of rest.

Paper or electronic?

As so often, a compromise may be the best solution. I use an electronic charting app on an iPad to create an initial ‘automatic’ route and to determine the overall distance. On mine, I can additionally overlay AIS contacts as an aid to collision avoidance.

I use paper charts as a back-up to record the boat’s position at regular intervals and to show other details and notes. In my opinion, it would be imprudent to sail without, at the very least, small-scale paper charts which cover the whole of your cruising area.

All charts are only as accurate as their latest corrections. There is some confusion about the timeliness and validity of electronic chart corrections, whatever the manufacturers may claim. UKHO and others, notably Imray, produce officially authorised corrections for their paper charts, and these can be viewed online or printed off in order to check that your electronic charts are actually up-to-date.

Contingencies

However well you plan, at some time you will be caught out by weather, seasickness, gear failures or threatened mutiny. This is when you need to have alternative plans ready to put into action.

As a minimum, you should have identified ports of refuge which are accessible in the prevailing conditions, and have done some homework on a safe approach and entry. In the early stages of our Dartmouth to Jersey run, this might involve a return to the Dart or a downwind sail to Plymouth. Later, Cherbourg or Guernsey could be options. In the final approach to Jersey, shelter from the south could be found in one of the bays on the north coast.

Communications

Make a note of radio stations and frequencies for weather forecasts, and look up any relevant VHF channels which you might need on passage, particularly port/harbour radio, working channels for local coastguard stations, MSI broadcasts etc.

All this information can be found in an almanac and may be a lot easier to reference than searching around online.

Shore contact

Finally, make sure that you brief someone ashore of your plans. They should be aware of your planned times of departure and arrival (ETD/ETA), and what action to take if you are overdue. To avoid unnecessary worry, keep them up-to-date with your progress whenever you have a phone signal, and be sure to let them know when you have arrived safely.

Our next-door neighbours have been our shore contact for many years, and they are fully briefed on our plans, contact numbers and the procedure to follow in an emergency. They are keen users of the Marine Traffic website and, on the rare occasions we have forgotten to report our arrival, have been known to text us with our position.

Recording the plan

After all your hard work, you need to record it in a format which is both clear and useful. You can then refer to it during the passage and, should you ever have to do so, prove that you complied with the requirements of SOLAS V.

A suggested pro forma is in the navigation chapter in Reeds, and is reproduced here. You can adapt it to meet your particular needs and preferences.
Some of the information will also be recorded in the logbook. An hourly note of barometric pressure, for instance, can give you an early heads-up of a change in the weather.

Be wary of keeping too much in an electronic format; paper will survive a soaking quite well and it won’t be destroyed if it is dropped or sat on.

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