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Nautical Charts: Raster vs. Vector Charts

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A Vector Chart on App Screen
vector chart

Vector Charts

Vector charts, also called ENC charts, are a graphic format in which charts are presented in a more schematic manner. Compare the app screen shot of the vector chart above (from the Navionics app) with the equivalent raster chart app screen shot on the preceding page (from the Memory-Map app). The screen presents less information about land and other features, and water depths are presented more by color layers than by soundings. As you zoom in, the information changes, however - it doesn't just get larger as on a raster chart zoom. You will see more depth soundings, for example, but the type used will always be the same. (If a number is hard to see on a small smartphone screen, it won't get any larger when you zoom in.)

The advantages of vector charts include:

  • Less electronic storage room is required; most apps and programs using vector charts include all U.S. waters, so you don't have to get more charts when you go to a new area. (Some chartplotter companies using proprietary versions of vector charts may still charge you to get more regions.)
  • Zooming in and out makes movement between small- and large-scale charts unnoticeable and seamless.
  • Vector charts have a "clean" look because they present less information on any one screen.
  • Programs and apps using vector charts often build in additional features or layers including information about marinas, social features, etc.

The disadvantages of vector charts include:

  • Less information is presented, depending on whose vector version you are using. As in the chart shown, land features and names are seldom included - this can be disorienting to mariners used to paper charts and road maps.
  • Some specific information (such as descriptive buoy data) does not appear on the screen unless you select it or move a cursor to it - compared to always being there on a raster chart.
  • It can be confusing to look back and forth between the wide view of large paper charts and the small section seen on an electronic screen.
  • A learning curve is needed to use a vector chart accurately at the appropriate levels of zoom.

Overall, the choice between raster and vector charts is mostly a matter of personal taste, since both are generally equally accurate and reliable for electronic navigation. Many software programs include both and give you the choice, whereas most apps use only one or the other, making it an important decision before choosing the app.

Speaking just for myself, I prefer raster charts because of all the information presented and the familiar appearance matching my paper charts - and I'm willing to work around the disadvantages. But I've sailed much with others using vector charts and understand their appeal as well. Most important, read reviews of different navigation products before making your own choice.

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