Thematic maps are a great way to illustrate concepts that have a connection to geographic areas. Currently Maprosoft supports Choropleth Maps.
Thematic maps are displayed by specifying a 'theme' parameter in the URL. The components of the theme parameter are as follows:
|key||The key identifies the data that the theme is based upon. The key either a field within a Microformats or one of the keys in a KeyValue microformat.||Yes||N/A|
|featureTypeName||The name of the type of data that the theme relates to. This must correspond to a feature type name. See the map data introduction page for an understanding of feature types.||No||If no feature type name is specified, the theme will be applied to all feature types available to the map.|
|min||This identifies the minimum value that the data of the theme should have. This is used to determine the color to apply to each feature.||No||0.0|
|max||This identifies the maximum value that the data of the theme should have. This is used to determine the color to apply to each feature.||No||100.0|
|colors||This identifies the color gradient to use. The allowed values are blues, greens, greys, oranges, pinks, purples, reds, reds-greens and yellows.||No||The reds-greens color gradient is used if not specified.|
Here is an example of a theme parameter to display parks with BBQs:
The following illustrates the color gradients where the data with a value of min (specified by the theme) will have the color shown on the left, whilst data with a value of max (specified by the theme) will have the color shown on the right.
A choropleth map shows information that is averaged or summarised at a regional level such that the regions are colored according to the data. For example, the map at the top right of this page shows the parks with and without BBQs - parks colored red do not have BBQs whilst parks colored green do have BBQs.
Range Based Choropleth Maps
A range based choropleth map shows information based on data that has a range of values. The data (specified by the key of the theme) must be a floating point value. Each value is then converted to a color based on the theme's color gradient and comparison of the data value to the theme's min and max values.
Boolean Based Choropleth Maps
A boolean based choropleth map shows information based on data that is either true or false. False values will be rendered with the left-most color in the theme's color gradient. True values will be rendered with the right-most color in the theme's color gradient.