Node-link diagrams are the most common graphical representation of networks. In a node-link diagram, the nodes are drawn as point marks and the links as line/curve marks connecting the nodes. Node link layouts are the subject of their own field of study—graph drawing—and countless algorithms for node-link layouts have been developed [BETT98]. Schulz and Schumann [SS06] distinguish between free layouts, where the node layout is not restricted, an example of which is the force-directed placement; styled layouts, where the node positions are determined by a predefined scheme, such as a grid, or a radial layout; and fixed layouts where the position of the node is determined by an attribute, such as latitude and longitude on a map. In fixed layouts, the only degree of freedom is conferred to the drawing of the edges connecting the fixed nodes.