====== Symbology ======
  * symbols can be either .gif or .png
  * for .pdf output, 8-bit png's must be used (PNG24 won't show transparency)
  * pdf library can't nhandle transparency in vector mode, so OUTPUTFORMAT needs to have this:
    * FORMATOPTION "OUTPUT_TYPE=RASTER"
    * (this will cause all layers to become raster, but transparency will work)

===== Example Symbols (German) =====
<code>
#
# Start of symbol definitions 
#
SYMBOL
 NAME 'gestrichelt'
 TYPE ELLIPSE
 POINTS 2 2 END
 FILLED true
  STYLE
  2
  2
  2
  2
  END
END

SYMBOL
 NAME 'gestrichelt2'
 TYPE ELLIPSE
 POINTS 2 2 END
 FILLED true
  STYLE
  4
  2
  4
  2
  END
END


SYMBOL
NAME 'Hauptstrasse'
TYPE VECTOR
 POINTS
 1 1
 3 1
 3 3
 1 3
 1 1
 END
END

SYMBOL
NAME 'Strasse'
TYPE VECTOR
 POINTS
 1 1
 2 1
 2 2
 1 2
 1 1
 END
END

SYMBOL
NAME 'Eisenbahn'
TYPE VECTOR
 POINTS
 2 1
 2 2
 1 2
 1 1
 2 1
 3 1
 3 2
 2 2
 END
END

SYMBOL
 NAME 'circle'
 TYPE ELLIPSE
 FILLED TRUE
 POINTS 1 1 END
END

SYMBOL
 NAME "downleft"
 TYPE VECTOR
 TRANSPARENT 0
 POINTS 1 0 0 1 END
END

SYMBOL
 NAME "downright"
 TYPE VECTOR
 TRANSPARENT 0
 POINTS 1 1 0 0 END
END

SYMBOL
 NAME "updown"
 TYPE VECTOR
 TRANSPARENT 0
 POINTS 1 0 1 1 END
END

SYMBOL
 NAME "leftright"
 TYPE VECTOR
 TRANSPARENT 0
 POINTS 0 1 0 1 END
END

SYMBOL
 NAME "box"
 TYPE VECTOR
 TRANSPARENT 0
 POINTS 1 0 1 1 0 1 END
END

SYMBOL
 NAME "diabox"
 TYPE VECTOR
 TRANSPARENT 0
 POINTS 0 0 1 1 -99 -99 0 1 1 0 END
END

SYMBOL
 NAME "point"
 TYPE VECTOR
 TRANSPARENT 0
 POINTS 2 2 2 2 END
END


SYMBOL
 NAME "drline"
 TYPE VECTOR
 TRANSPARENT 0
 POINTS 5 5 2 2 END
END


SYMBOL
 NAME "dlline"
 TYPE VECTOR
 TRANSPARENT 0
 POINTS 5 2 2 5 END
END

SYMBOL
 NAME "cross"
 TYPE VECTOR
 TRANSPARENT 0
 POINTS 1 1 END
END

SYMBOL
 NAME "dash_line"
 TYPE ELLIPSE
 FILLED true
 POINTS
 2 0 
 2 4
 -99 -99
 0 2
 4 2
 END
END
</code>