To get around in a different country, a new town, or a college campus, or to use the subway system in a big city, you might need to use a map.  A map is an image that is similar to the real thing.  Each point on the map corresponds to exactly one point in the area that the map describes.  This correspondence is called a mapping or a transformation.  A transformation maps a preimage onto an image.  In this unit, we are going to study several transformations, including translations, reflections, rotations, and dilations.