Zooming, brushing and rotating

Maps can contain a lot of information, much more than a viewer can grasp. If you fill a map with all the information you have, it becomes unreadable. Web-based maps should be interactive. A typical viewer expects to zoom in for details, zoom out for context, and pan when necessary. At the beginning of this chapter we added simple SVG zooming and panning to a map with the d3.zoom() behavior and SVG transforms. In this section we will explore other techniques that take advantage of the three-dimensional nature of maps to achieve the best zooming and panning experience.

Brushing, or zoom to bounding box

One way to zoom in to an area in a map is to draw a box, clip the box and expand it so that it...