Passage Planning :  When you plan a passage or
voyage, it is best to look at an overview chart. I prefer paper
charts for this. You may wish to refer to an Almanac or Pilot
book to give you information about navigational hazards en
route. If the trip will take more than a few hours, you should
note down alternative ports or anchorages en route. Then
in the event of bad weather, gear failure or other emergency
you can divert without any further planning. You will need to
factor in tide directions and rates, particularly at headlands,
where you might have a tide gate (see issue 24). Once
this overview is established you can begin to work on more
detailed charts of a smaller area. On these you can work out
where to put your WPs, to keep you clear of hazards. Don’t
forget to make extra WPs for the divert ports or anchorages.
By now, using your boats average speed, you will have a
good idea of the timing of your passage, with an expected
time of departure (ETD) and an expected time of arrival
(ETA). Your WPs should now be in the GPS which will give
Typical laptop with chart management software
you a distance and course to steer between WPs. For best
practice you should now plot the WPs on the paper chart.
Chart Corrections: Corrections are required on all
With the distance and courses worked out independently.
charts in order to keep up to date with the various changes.
You will be able to see if any do not match the GPS readout.
These are usually done on an annual basis. Paper charts
In this way you can cross check and avoid mistakes.
can be sent back to the manufacturer for updating or can
be updated by the user, using information given out by the
Pilotage : Here we are looking at the process of
British Admiralty in “Notice to Mariners” or from the chart
navigating in or out of port by visual observations of
manufacturer. Electronic charts are updated by returning the
recognisable landmarks or navigational aids.
memory card to the manufacturer for this to be done.
Let’s look at the problem of entering a minor port we have
not visited before.
Whilst chart plotters and laptops are valuable tools, we
have to accept that they are likely to fail at some point. As To enable us to do this effectively we will have a large
mentioned above, some chart plotters use the same screen harbour chart to work from, or a pilotage chart from a pilot
to display radar information as well as chart information. If book. On this we can look out for any helpful buoys, charted
the screen should fail, then you have lost both the chart and depths, conspicuous objects, compass bearing entry lines,
radar displays. All electronic instruments are liable to faults etc. On arrival at an unfamiliar port it is best to have your
and power failure and we will need sufficient paper charts to pilotage information already noted down. What will we see
enable us to continue our voyage or navigate to the nearest first? Is there a buoyed channel? What is the safe approach
safe port. Knowledge of how to use the paper charts to bearing? Are there any rocks or shallow areas? Are there any
fix our position and plot a course to steer is essential. This useful transits? (a “transit” is a compass bearing line between
fundamental skill should be kept alive by regular use at sea. two conspicuous objects).
GPS has made navigation more accurate and enabled sailors
The entry then is divided into stages. For example : arrive
to venture further than they might otherwise have done.
at mark A, then steer X compass course to arrive at mark
Most yachts now carry a spare GPS as backup. If you have
B, then we should see mark C which is a transit to take us
a spare onboard remember to switch it on regularly, because
to mark D. If we will be entering at night there may be two
units that are seldom used can sometimes take a very long
leading lights that will guide us into port by keeping the
time to initialise themselves on start up. I once met a yacht
lights in line (a transit), or perhaps sectored lights with red,
crew in the Canary Islands who were just about to cross the
green or white lights. By keeping in the white sectored light
Atlantic and they had on board no less than five GPS sets,
as you approach, it may keep you away from hazards. If
but no sextant or navigation tables. If you are sailing offshore
this information is noted down before arrival it will be much
or crossing oceans it would be advisable to learn Astro
easier and less stressful to make the entry. If we are entering
navigation. There are many self learn books on the subject.
a large or commercial port we must keep a good lookout for
Of course the RYA also run courses.
ships and fishing vessels and give them priority in restricted
channels. It is always a good idea to monitor the port’s
The essence of GPS navigation is the use of waypoints (WP).
working VHF radio channel as it will give you information on
A WP is a known lat and long position, which is given a name
vessel movements.
or number and entered into the GPS. If you wish to steer
from one to another, a line drawn between the two would be
As well as working from the chart, you may find a lot of useful
called the track line. If on your journey, your boat was set
information in Pilot books or Reeds. Harbour authorities often
to one side or the other off track, the resultant error would
publish their own visitor’s guides that are very useful.
be called cross track error (XTE). The ability of the GPS to
monitor XTE is a useful feature, as you can avoid dangers by
Next month we take a look at Manoeuvring and
staying on your track line, but only if you have placed your
berthing and how monohulls differ from multihulls in
WPs in the correct places.
their manoeuvrability.
20  MULTIHULL REVIEW : MARCH 2009JUNE 2009
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