This chapter discusses three of the fundamental attributes of a map, namely, the scale , symbolization , and projection , and reviews the data concepts of levels of measurement and classification, important in building thematic maps. Maps serve a variety of purposes and can assume a huge variety of formats. Common examples of reference maps include country maps, road atlases, or the search results on Google Maps. Many countries now produce and publish large-scale maps of topography , reference maps that show the shape of the land and various other features. Thematic maps are designed with a specific purpose in mind. They are often intended to explore the spatial distribution of a selected phenomenon in the context of a larger project. Isopleth or isoline maps use the same technique as contour maps but use isolines to represent an appropriate geographic phenomenon. Choropleth maps have become an especially common type of thematic map over the last several decades.