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Chart Plotting Technology

By Captain Bob Figular, reprinted with permission from Mariner’s Learning System

Through the ages navigators have constantly been in search of new technology that makes identifying the position of their vessel easier and more accurate. Now, to a very large extent, GPS can be relied upon to take care of this task. The problem that exists with this technology though is that even with quick plotting techniques; a human navigator working on a paper chart simply cannot keep up with the flow of information available from their GPS receiver.

One solution is to use a chart plotter to display the boat’s current position on an electronic chart. However simple this process may appear don’t be fooled by the simple nature of this technology. Plotters do have their drawbacks, but their great strengths are that they update the position continuously, without human intervention, and without introducing such very human errors as plotting 55°45′.6N instead of 55°46′.5N.

Even the most basic plotters, allow you to mark waypoints, plan routes, and measure directions and distances, while some can even work out the course to steer to allow for tidal streams, or plan the optimum route to follow to allow for forecast changes in wind strength and direction. They can then show how your actual position compares with your plan, give simple steering instructions to a human helmsman, or control an autopilot.

Any chart plotter is a combination of three main groups of components:

  • Hardware
  • Cartography
  • Software

The hardware is the physical equipment (the casing, display, control panel, etc.) and the internal electronics, such as the power supply, processor and memory. It may be designed from the outset as a chart plotter; it can be combined with some other equipment such as radar or an autopilot or it could be housed on a desktop or laptop PC or with today’s technology even a PDA (Personal Digital Assistant) or Smartphone.

The cartography refers to the electronic charts. They are available from various sources, in different formats and on different media, such as CD-ROMs, flash memory cards, or custom-made cartridges of various shapes and sizes.

The software is the link between the two, converting the electronic cartography into a form, which can be displayed on the screen, enabling us to carry out navigational tasks, and communicating with other electronic equipment such as a GPS receiver and autopilot.