Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition

Thinking about Maps Again

Now that the connection between the table and the map is firmly re-established in your mind, we turn back to the map itself. You could broadly classify maps into two categories: general-reference maps and thematic maps. Many maps, like road maps or topographical maps are used for general information, navigation, topology, and to show locations of features. Thematic maps (sometimes called statistical maps), on the other hand, show polygons that divide up the landscape into distinct areas; the areas are coded—with color or other symbolization—to indicate the value of a characteristic or attribute about each individual area. So, in a sense, attribute information is reflected directly, visually, on the map; in GIS you find this information mostly in tables. (Description of areas somewhat true for general-reference maps as well, but in thematic maps this information is the primary reason for the existence of the map.)