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Thematic mapping is the production of maps to express information about a specific phenomenon. Examples of thematic maps include: polygons representing sectors of a city colored differently based on the crime rate of each sector; points representing cities displayed using different symbol sizes based on the population in the city, etc. In JMap, you can create thematic maps using the bound attributes of a layer. Depending on the values of their attributes, map elements will then be displayed differently. Using JMap Admin, you can create as many thematic maps as you want and you can also create many thematics using the same layer.

In JMap, there are 2 main categories of thematics: classifications and proportional quantities.

To create a thematic, press Create in the Thematics section of the layer settings.

Classification

Thematics that use a classification will separate map elements into a finite number of categories (also called classes), each having a specific style. When a map element belonging to such a thematic is displayed, it uses the style of the category it is part of in order to render itself on the screen.

Creating a graduated styles thematic

Graduated styles thematics use a graduation of one or more visual variables to represent the elements of the different categories. Examples of such graduations include: the fill color of polygons that is graduated from white to red, the size of point symbols that is graduated from size 1 to size 5, the line width of elements that is graduated from 1 to 4, etc. In all cases, there is a finite number of categories and every element of the layer falls into one of those categories. Only a numeric attribute can be used for this type of thematic.

To create a new thematic of this type, you need to select the numeric attribute to use, define the number of categories, select the range calculation method, and define the category styles.

There are several methods for calculating the ranges of values for the categories of this type of thematic. See Methods for calculating ranges for more information.

The next section allows you to define the styles of the categories. There are two possibilities: create custom range styles or use predefined color schemes.

Custom range styles

You must define the from and to values of the style by indicating the style variables that will vary (e.g. border thickness, symbol size, fill color, etc.). The category styles are then generated by interpolation between the from and to styles. Optionally, a third style can be used to create an inflexion point. If an inflexion is defined, the generated styles will pass through the inflexion point at the specified position in percentage. The interface is different based on the element type of the layer.

Color schemes

Instead of manually defining styles, you can select a color scheme to generate the styles of the thematic's categories.

Creating a graduated symbols thematic

Graduated symbols thematics draw symbols superposed on the elements they qualify. The symbol sizes are graduated according to a finite number of categories based on a numeric attribute. The symbols can be used with any type of map element. Only numeric attributes can be used for this type of thematic.

There are several methods for calculating the ranges of values for the categories of this type of thematic. See Methods for calculating ranges for more information.

The creation process is the same as for creating a graduated styles thematic, as described above.

Creating an individual values thematic

Individual values thematics represent all elements that have the same attribute value with the same style. This type of thematic is not using a range of values for each category but rather a specific value. The maximum number of unique different values is 512. If your layer has more different values, it will not be possible to create this type of thematic on that layer. Numeric and alphanumeric attributes can be used with this type of thematic.

To create a new thematic of this type, basically all you need to do is to select the attribute to use.

JMap proposes random colors for this type of thematic. You can modify styles manually or click on Color Schemes to use a predefined color scheme.

Creating an individual custom values thematic

Individual custom values thematics are similar to individual values thematics except that you can define your own values, instead of being limited to values already present in the data. This is useful when you create thematics using a data set that does not contain all the known possible values for an attribute. When new data is later added to this data set, the new values will be handled properly by this type of thematic.

The creation process is similar to creating an individual values thematic, except that you have the option to modify the list of individual values by adding, removing or modifying categories.

Proportional quantities

Proportional quantities thematics represent map elements using a continuous variation of a visual variable (e.g. symbol size, fill color, etc.) based on a numeric attribute or set of attributes.

Creating a proportional symbols thematic

Proportional symbols thematics draw circular symbols superposed on the center of the elements they qualify. The symbol sizes are determined by interpolation between the minimum and maximum values of the attribute. Only numeric attributes can be used for this type of thematic.

To create a new thematic of this type, you need to select the numeric attribute to use and define the from and to styles. The symbol size and color will be interpolated between the from and to values.

Creating a pie charts thematic

Pie charts thematics draw pie chart diagrams on the center of the elements they qualify. This type of thematic works with one or many numeric attributes. Each part of the diagram (piece of the pie) is associated with a different attribute. The size of the diagram is proportional to the sum of the attribute values. Only numeric attributes can be used for this type of thematic.

To create a new thematic of this type, you need to select one or more numeric attributes to use and define the chart style.

Creating a bar charts thematic

Bar charts thematics draw bar chart diagrams on the center of the elements they qualify. This type of thematic works with one or many numeric attributes. Each bar of the diagram is associated with a different attribute. The size of the diagram is proportional to the sum of the attribute values. Only numeric attributes can be used for this type of thematic.

The creation process is similar to creating a pie charts thematic, as described above.

Methods for calculating ranges

Several different methods can be used to calculate the ranges of values for the categories of thematics using classifications. These methods are described below.

 

Once the thematic has been created, you are brought to the interface that displays its general information and that allows you to specify the legend, give titles to the classes, and edit or delete the thematic.

Click on to save the settings.

For classification thematics, you can unselect classes you do not want to display, and you can also give a title to each class. Click on to save the settings.

Enabling and disabling thematics

Enabled thematics are displayed automatically when the layer is displayed in JMap on the client. Disabled thematics are still available but are not displayed by default. They need to be enabled by the user to be displayed. You can enable and disable thematics from the thematics section in JMap Admin.

Reordering thematics

In JMap applications, thematics are displayed in the order they are defined in JMap Admin. It is important to set the order appropriately because some thematics can completely hide others if they are placed on top. Use the Modify menu from the list of thematics in order to modify their order.