A quiver plot is a special point style where the direction of the symbol and the size of the symbol are derived from attributes. This styling is often used to show wind direction, currents, etc. The quiver plot can be derived from either direction and magnitude attributes, or from U and V values. Quiver plots can be applied either at the layer level or on a set of selected points.
Use Quiver Plot
To apply a quiver plot to all the points in a layer, double click on the layer in the Control Center, or highlight the layer and press the Options button. Choose the Point Styles tab and select the Quiver Plot option at the bottom.
Press the Options... button to access the options described below that control the styling and attribute basis for the quiver plot.
Like other point styles, the quiver plot can be applied as a style to only a subset of selected points in a layer.
To access this option, select the points, then choose Create Quiver Plot (Direction Vectors) from selected points from the Digitizer menu or context menu under Create Point/ Text Features or Attribute/ Style Functions.
Quiver Plot Options
The Quiver Plot (Direction Vector) Options dialog (below) allows the user to specify the arrow symbol and attributes to be used when displaying point data as a quiver (arrow) plot. The arrow will point in the direction calculated from the attributes. The size of the arrow will be scaled relative to the largest magnitude value. If no magnitude is specified, all of the arrows will be the same size.
Specify the symbol to use by choosing an arrow symbol from the Arrow Symbol list.
Use a UV Vector - When this option is chosen, the specified attributes must contain a UV vector. The U component is the vector value in the X direction. The V component is the vector value in the Y direction. These values represent the orthogonal velocity components which define the strength towards the North and towards the East. These two values will be used to compute the orientation and size of the vector symbol.
Use Direction and Magnitude - When this option is chosen, the user must choose an attribute containing the direction (in degrees, relative to 0 pointing at the top of the map, drawn clockwise), and another attribute containing the magnitude. The magnitude is optional.