Charts and electronics

Has anything really changed?? Electronic charts have simplified navigation, but nothing is foolproof to a sufficiently talented fool. Skippers need to remain wary.

Sitting on the lower spreaders to see the deep water in the passes through the coral reefs, a folded chart of the Fiji coast on my knees, a square protractor and pencil in pocket and hand-bearing compass on a lanyard was quite normal. Karin sailed the boat while our two-year-old son was entertained with a packet of chocolate biscuits. At sea, sextant sights at morning and noon, laboriously calculated and plotted, gave a position within about five miles, provided we could see the sun. A vigilant check for coastal lighthouses when nearing land stopped us from getting bored.

Then satellite navigation (satnav) came along, magically giving a position every few hours even when it was cloudy. When GPS arrived and gave continuous fixes, everyone turned into a navigator. But we still needed to plot a track amended by fixes on a paper chart with a pencil.

We quickly accepted that a GPS fix was good. Over time the reliability and accuracy increased and bearings from a hand-held compass were relegated to the back-up role if all else failed.

GPS became so accurate and reliable that many vessels hit rocks having assumed they had accuracy to within a few metres at all times. Where a safe distance from dangers used to be a mile, it had now been whittled away to nothing.

We thought it was incredible that the position fixing systems were electronic – but then even the charts appeared on-screen.

Before we look at these changes and their impact on safety, it’s wise to reflect on basic navigation concepts.

NAVIGATION 101

“It’s a chart, not a map.” This is the first lesson we were told in a navigation class. “Those crosses are rocks and the little numbers on the blue bits are water depths,” and so on. All those symbols and little pictures have meanings; some are more important than others.

No matter whether the chart is paper or electronic, the symbols remain as important as ever – along with the need to understand them instantly. So does the need to have the maximum detail possible and that means having the largest scale chart available for the area in which you are navigating.

Two hundred years ago, there were two fundamentals required for safe navigation:

and These haven’t changed. Know your position - The search for a reliable method of determining position at sea was always the holy grail in navigation and it has taken more than 500 years to get there. Every generation made improvements and the current generation has the benefit from all that has gone before.

Stay ahead of the ship - Know where you will be, whether it’s a few minutes ahead while piloting up a creek or a day or two ahead on the ocean. You can always adopt Plan B if something changes but if you know where you expect to be, you have time and information with which to assess what is happening and to think through what needs to be done.

For example, in event of bad weather approaching, an emergency or sudden fault onboard, or even a change of mind to catch up with other cruising friends at a different destination from what you had intended.

Events such as the Rena grounding on Astrolabe Reef and Team Vestas Wind sailing onto a reef in the Indian Ocean occur when navigators neglect to zoom in on the large scale electronic chart to see its essential details. But the fundamental mistake was no different from the past when many wrecks came to grief on reefs because the navigator had not consulted the large scale paper chart.

A set of NZ electronic charts is either free or, if Navionics charts are selected, about $70 will buy a complete set of charts in full detail for all of New Zealand, Australia and the Tasman Sea. Navionics charts giving full detail of cruising in the UK, Europe and the Mediterranean cost about $150, a fraction of the cost of equivalent paper charts. When cruising, a paper chart may be used just for a few hours or not used at all.

We carry on board about 300 paper charts and without electronics that number would have to double. Aside from the cost, there is inconvenience of storing them and the considerable weight. Add to that the physical handling and sorting and it’s obvious why electronic charts have taken over in an electronic world.

It is important to have up to date information, but an old chart is better than no chart. It is impossible to keep paper charts up to date on small vessels cruising widely but entire folios of electronic charts can be updated on-line in a few moments.

RELIABILITY

Electronics need a sure source of electricity and are vulnerable to uncontrollable events such as lightning. Equipment can break down at any time. Paper charts, compass, sextant and timepiece are possibly more robust, although I can recall a yacht race during which the sextant was dropped and damaged. On the other hand, the calculations and plotting on paper charts has to be done by a human, surely the least reliable factor especially when that human is cold and tired.

The number of small craft is growing rapidly, but the number getting lost or running aground has not increased in line with boat numbers. If anything, the number of such incidents has reduced over time in spite of more skippers who have limited knowledge of conventional navigation. Today almost all rely heavily on electronics.

While we can know where we are within metres almost all of the time, the charts may have considerable errors in latitude and longitude and the errors may not be consistent across the chart. Not only is this a problem with paper charts, in some parts of the world such as Chile, electronic charts can have errors of several miles.

SELECTING THE SYSTEM

Many options are available with some vessels having full integration with the chart-plotter, GPS, radar, AIS, autopilot and