Quite simply, as the label suggests, it is a map of a theme or topic. Thematic maps have almost infinite variety and include most of the maps in the media showing, for example, the spread of fire ants, the status of sales taxes by State, or world population density. Thematic maps may be quantitative or qualitative . Quantitative maps portray numerical information, such as numbers of crimes in an area or crime rates.
Crime analysts use both quantitative and qualitative maps.
Nominal measurement names or labels items in unordered categories, such as race. If a map shows homicide victims by race, it is a qualitative thematic map. Mapping by race, age group, or marital status puts labels on groups without ranking them as higher or lower or better or worse. For example, the number of incidents affecting racial groups by areas can be counted, thus combining qualitative and quantitative interpretations. Thus patrol areas or precincts might be ranked according to their crime rates, their incidence of complaints, or the average seniority of officers.