Do You Really Need a
Marine GPS Chartplotter?

As the name might suggest, a marine gps chartplotter is a marriage of electronic chart software and GPS technology combined in a single display.

Marine chart plotters come either in the form of a software package installed on a laptop computer, or a dedicated instrument. Each has its merits, and both rely on an interface with a GPS signal.

The screen is normally larger on a laptop, but some will argue that its vulnerability as a portable device makes it less attractive than a dedicated plotter, most of which are marinised and fully weatherproof.

But if you already have a laptop and want to save a few bucks, then the laptop route may well be the way to go - particularly so now that fully functional free chart plotter software can be readily downloaded from the internet - but you won't get the same extensive functionality as you'd get from a bespoke unit.


A Marine GPS Chartplotter - Luxury or Necessity?

I failed to get excited by marine GPS chartplotters for a long time, preferring paper charts that filled the entire surface of my chart table rather one which only filled a small screen - if I'd thought about it a little longer, perhaps I'd have realised they weren't mutually exclusive.

But while reviewing the options for a new radar installation at the London Boat Show, I was persuaded to play around with a multi-function display unit on a manufacturer's stand.

Not only was it possible to switch between the radar display and the chart plotter display, you could also view them simultaneously in 'split-screen' mode. But what did it for me was the overlay mode.

This enabled the radar display to overlay the chart display, with zooming in and out making it much easier to interpret when close to shore. I didn't stand a chance - it had to be mine.

Installed at the chart table and fully integrated with wind, log and depth instruments it's become a very useful aid to both navigation and passage planning aboard Alacazam and supplements - not replaces - my paper charts.

With my intended route shown on screen, and Alacazam's position marked by an icon, a deal of valuable information is shown graphically. For instance:~

  • The true (or relative) wind strength and direction is shown as a vector arrow at the icon, and similarly another arrow shows the combined effect of set and drift;
  • A projected course line shows where we'll be going if all else remains constant;
  • A track line shows where we've been. If this is parallel to the desired course and not to windward of it, we're doing OK. If it's diverging from the desired course and we can't sail any closer to the wind, then we'll need to tack at some stage, and it's often clear to see when this will best be done.

Recently I've linked an AIS (Automated Identification System) to my marine GPS chartplotter which further increases its functionality.

So is a marine chartplotter a luxury or a necessity?

It's definitely a luxury, but a very attractive one - I wouldn't want to be without a chart plotter now.



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