Chart Display Appearance

The IHO standard S-52, often referred to as the "Presentation Library", decribes the appearance of ENC charts in great detail by providing precise definitions of all symbols, colors, linestyles and fill patterns along with their alignment and drawing order. The Despina engine displays ENC data in compliance with the latest Presentation Library (currently version 3.4).

For the highest quality chart display, we use state of the art rendering techniques:

  • Pure vector graphics: All visual elements - the symbols, line styles and fill patterns - are defined as vector graphics and can therefore be scaled to arbritrary sizes and for different dpi resolutions without degrading quality. Geomaris will provide a vector symbol editor for creating customized symbols, lines styles and fill patterns.

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The above images show the same map section using different scale factors for symbols, line styles and fill patterns.

  • Full antialiasing: All visual elements are drawn antialiased for a clear and aesthetically appealing chart display.

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Click to to enlarge.

 

Dynamic Aspects

The high frame rates enable applications to support smooth zooming and camera flights. As a consequence the user experience is not determined solely by the visual apperance of each single chart image but also by the dynamic behaviour of the chart elements in motion. The user shall not be distracted by this dynamic behaviour during chartwork.

Therefore Despina introduces techniques to handle these dynamic aspects:

  • Text labels: The Presentation Library groups text labels into text groups for selection and prioritization. When zooming out, text labels are smoothly fading out before intersecting with another text label. The text priority is accounted for to determine which of the two colliding text labels is suppressed. When zooming in, respectivley, the labels are faded in when there is enough space to show them.
  • Centered symbols: The Presentation Library requires that some symbols are placed at the center of the part of an an area which is visible on the screen. These so called centered symbols do not drift or jump during zooming or scrolling. Instead after the zoom or pan operation the symbols are faded out at their old position and simultaniously faded in at the new correct position if neccessary.
  • Dynamic decluttering: Despina dynamically hides sounding labels to prevent clutter. You can learn more about Dynamic Decluttering in this article.
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