General maps show a variety of features, such as geographical, political and cultural elements.
Topographical maps show elevation using contour lines and important physical features within an area. They typically show human settlement with roads, towns and cities, and provide locational references such as latitude and longitude or grid lines.
Thematic and statistical maps use the base data as a reference point for the map. These maps use different methods to encode and display data, such as:
- dot density, where each equal-sized dot represents a fixed unit of data and is placed where the data occur
- proportional symbols, where the same symbol is scaled to represent different data values for different locations (note that areas of symbols are difficult to compare accurately)
- shaded distribution, or choropleth, where shaded or patterned areas represent gradations in the data, such as percentages, densities or discrete data types; typically, low values are in a light shade, stepping up to high values in darker shades.