PART 6
Any electronic chart contains all the information available within its boundaries, regardless of scale. If all this data were displayed, the chart would be unusable, so the plotter filters it for you. As you zoom in and out for an overview or more details, features appear and disappear. The plotter’s default is often to center its view on your vessel, but if you need to see what’s happening elsewhere you can move across the chart, then zoom in or out again. This method is the only way of using electronic charts. The more you do it, the easier it becomes, but the watchword is that unless you zoom right in, the chart may be hiding something vital.
GPS Settings
Check the default settings of your GPS and modify them to suit your needs. Here are some settings to consider. • Datum (WGS84 is standard, but must agree with the datum used for your chart) • Speed (knots) • Distance (nautical miles) • Time (24-hour clock and local time)
• True or Magnetic North • Latitude & Longitude (de- grees, minutes, decimals of minutes)
The lighthouse structure (inset) indicates danger- ous surrounding rocks or rip-rap by the greenish brown area around it.
An electronic chart zoomed in tightly – note that there’s lots of useful close-in detail, but overview is non-existent.
The same lighthouse shown inset above indicates no rip-rap.
The same chart zoomed out for overview – note the lack of useful detail.
Plotters have menus full of tools but one of the easiest to access is often Declutter. This chart has been decluttered to clarify the overview. However, much vital detail is obscured.
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With Declutter switched off, depths and other im- portant data are visible. It is critical never to leave a chart decluttered and to forget you have done so.
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