A spatial distribution is the arrangement of a phenomenon across the Earth's surface and a graphical display of such an arrangement is an important tool in geographical and environmental statistics

Environmental statistics

Environmental statistics is the application of statistical methods to environmental science. It covers procedures for dealing with questions concerning both the natural environment in its undistrurbed state and the interaction of humanity with the environment...

. A graphical display of a spatial distribution may summarize raw data directly or may reflect the outcome of more sophisticated data analysis

Data analysis

Analysis of data is a process of inspecting, cleaning, transforming, and modeling data with the goal of highlighting useful information, suggesting conclusions, and supporting decision making...

. Many different aspects of a phenomenon can be shown in a single graphical display by using a suitable choice of different colours to represent differences.

Examples

• Many police departments colour-code a city map
  City map
  A city map is a large-scale thematic map of a city created to enable the fastest possible orientation in an urban space. The graphic representation of objects on a city map is therefore usually greatly simplified, and reduced to generally understood symbology.Depending upon its target group or...
  
   based on crime statistics.
• The two-step floating catchment area (2SFCA) method
  Two-step floating catchment area (2SFCA) method
  The two-step floating catchment area method is a method for combining a number of related types of information into a single, immediately meaningful, index that allows comparisons to be made across different locations...
  
  has been used to prepare maps showing the relative accessibility of individuals (demand units) to physicians (supply units), by shading which shows different degrees of accessibility.