John Maurer wrote:
Dear MapServer Users,
Does anybody have experience displaying vectors in MapServer? By
"vectors", I don't mean the usual vector vs. raster difference. What I
mean is displaying data like wind vectors, which are point locations
that have both a direction (degrees) and magnitude (e.g. meters per
second). Usually these are displayed as arrows, which each point in a
certain direction and whose tails vary in length depending on the
magnitude each measurement. Is this possible in MapServer? Thanks for
any suggestions!
You could bind the symbol size and angle to an attribute in your layer
definition.
If you can precompute the size in pixels based on the wind speed and
store that to an 'arrowsize' attribute then you could use a layer defn's
like this:
LAYER
TYPE POINT
...
CLASS
SYMBOL 'arrow'
ANGLE [direction]
SIZE [arrowsize]
COLOR 0 0 0
END
END
If you can't precompute the arrow size in pixels, then you could use
classes based on the wind speed attribute:
LAYER
TYPE POINT
...
CLASSITEM 'windspeed'
CLASS
EXPRESSION ([windspeed] < 5)
SYMBOL 'arrow'
ANGLE [direction]
SIZE 10
COLOR 0 0 0
END
CLASS
EXPRESSION ([windspeed] < 25)
SYMBOL 'arrow'
ANGLE [direction]
SIZE 15
COLOR 0 0 0
END
CLASS
EXPRESSION ([windspeed] < 100)
SYMBOL 'arrow'
ANGLE [direction]
SIZE 20
COLOR 0 0 0
END
CLASS
# No expression ... catch all for windspeed > 100
SYMBOL 'arrow'
ANGLE [direction]
SIZE 25
COLOR 0 0 0
END
END
Daniel
--
Daniel Morissette
http://www.mapgears.com/
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