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Rotation Angles

April 24 2009 | 0 comments
Categories: Symbology

When using rotation angles for point symbol data, we have found that the angles are not precise with variations ranging from about +5 to -8 degrees. How can we plot point symbols at precise angles?

Mapping Center Answer:

Without seeing this, it's hard to get too specific.  One thing to understand about the display of rotated marker symbols is that you're working with rather limited display resolution, so the smaller the marker symbol, i.e., the fewer pixels used to display it, the less likely you'll see differences when changing display angles by small amounts.

Add to this, the idea that different types of marker symbols (character, picture, and representation) each have advantages and limitations. Character markers will generally display better on screen because the font contains information that your computer's display uses to fine the display (for instance if you change your display properties to use or not use the option to smooth the edges of screen fonts, you'll see a difference).  However, representation markers and picture markers do not have extra information, so their display is based on drawing the pixels based on how much of the symbol's geometry overlays the pixel (I'm just conveying the idea here, not the method).

That said, you should be able to set your reference scale, zoom in, and see the quality improve.  Printing would also improve this, though, again the resolution is the issue--you'll get different results at 300, 600, and 1200 dpi.

If you're seeing something that does not make sense relative to the above guidance, please contact technical support using your organization's usual channels.

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