A zoomable value which specifies the spacing between two consecutive shapes/icons on the line. This property only has an effect on linear features.
The spacing is specified as a multiplier of the shape/icon's size, so if you have a shape/icon that is 10 pixels long and the shape-spacing is set to 2, the actual spacing will be 20 pixels. The default value for shape-spacing is 2.
define shape-spacing : 11:1;13:4;14:6