Also, wind arrow colours may be associated with a text to describe the significance of the colours. Wind flags, plotted each time in the legend with a full barb, are associated with a text which describes the wind strength. There are special legends for image plotting and in observation plotting of analysis feedback data. The user has full control over the positioning of the legend box, the number of legend entries and the way entries are plotted within the box. There are parameters to control all the features and options in shading and their default values should ensure that, for most plots, a reasonable shaded plot can be achieved without having to set most of the shading parameters.
Polygon shading is where the area between contours is formed into a closed polygon and filled.
Cell shading, which is a lower quality shading than polygon shading, shades each cell according to the value of the field at that cell. Marker shading consists of plotting a marker at each of the grid points in the field. The type of marker and also the height and colour of each marker is determined by the value at the grid point. Figures 6 and 7 give examples of the shading methods and techniques. Shading enables more information to be plotted on a map without causing confusion.