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Nikos BarBas. Merchant Marine Chief Officer.

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Answers, for some logic questions:

What's necessary to use electronic charts? What's the difference between raster and vector charts? Which are best for you?

Two separate components: Electronic charting requires two separate digital components, the software needed to display the charts and handle navigational tasks and the digital charts themselves.

Raster charts:  A raster-scanned electronic chart is like an electronic snapshot of a paper chart. On-screen it looks just like the same familiar paper charts you've used for years. If you're using a color monitor, you'll usually see the original colors from the paper chart, though SoftChart uses a slightly different color palate. Raster charts are produced by Maptech and SoftChart in the United States, NDI in Canada, British Admiralty in England and by official hydrographic offices in a number of other countries. Although raster charts normally run on computers some dedicated plotters that raster charts. Raster charts are available in geographical groups and are distributed on CD-ROM. They are tried and true technology.

Vector charts: Vector charts are distillations of genuine paper charts, but their presentation is different. Vector charts can have virtually the same information as their raster equivalents. Until recently, vector charts were usually displayed on dedicated plotters with monochrome displays, but today more manufacturers are making plotters with color displays and much improved feature sets. The most popular vector charts (for plotters) in the world are made by C-Map and Navionics, and they come on proprietary cartridges.

Vector charts are also now available for computer-based electronic charting systems. Nobeltec, Transas Marine and MaxSea are all programs that use vector charts. Vector displays can allow you to view all or select "layers" of information to reduce clutter or add detail to your chart. And the depth soundings and other information are always very readable - no matter the scale or rotation of your chart. There are many other advantages. We like vector cartography and we and think you will too!

Which is best? Chart publishers argue about whether vector charts are better than raster charts or vice versa when running on a computer. We feel that each type has its advantages, and either type can serve you very well.