Over reliance on electronic charts

Over reliance on electronic charts

We asked Simon Wilson, Equinox Sailing’s Chief Instructor if there are any pit falls in using electronic charts for passage planning.

For many sailors sailing in familiar waters, they are aware of any navigation risks and possible major dangers they face while sailing in those areas.  For sailors who sail in the same waters on a frequent basis, they may choose not to look at a chart for shorter passages within the known sea area and choose to rely on a chart plotter.

However when sailing in less familiar waters does a reliance on the chart plotter in familiar waters make sailors complacent?

There are two main types of electronic charts, ‘Raster’ and ‘Vector’.

‘Raster charts’ are an electronic version of a paper chart, what you see is what you get.

‘Vector charts’ use layering to add and remove detail depending on the level of zoom. Most chart plotters use Vector charts because of their ability to show more information than a Raster chart.

We do however need to be aware that a Vector chart, if zoomed out, may not show detail such as a drying area or a rock, which would be considered dangerous.  It is therefore important if planning a passage on an electronic chart, that the whole route is checked and zoomed in enough to ensure that you spot any dangers.

The image below shows the ‘The Island’ very clearly as well as depth on the Raster chart, but not on the Vector Chart as it has not been zoomed in enough.

Raster chart