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MapInfo Monday: Getting Started with Thematic Maps

  • 1.  MapInfo Monday: Getting Started with Thematic Maps

    Posted 05-06-2024 03:28
    Edited by Peter Møller 8 days ago

    Happy #MapInfoMonday!

    Thematic Maps is a powerful way to bring attribute information to life in your map. Using a thematic map, you can convert an attribute value into a style and in this way map it. This allows you to see trends or discover correlations between your locations that would be impossible to detect by viewing your data in a spreadsheet.

    MapInfo Pro allows you to create several thematic map types. Below are just a few.

    In this article, I will give you a quick introduction to creating and working with thematic maps.

    Creating a Thematic Map

    You follow a similar process creating any of the several thematic maps that MapInfo Pro supports.
    Launch the Create Thematic Map wizard via the Add Theme control on the Map tab.
    Now select the Thematic Map Type you want to create. When you select a Thematic Map Type on the left, the Template List will refresh to show the matching templates.
    When you select a template from the list, you can see a preview on the right.
    Also note that under the Preview area, you can, for some templates, also control if you want to use the Customized Legend Text from the template and the Individual Categories from the template.
    A description of the Thematic Map Types, from the MapInfo Pro Help:
    • Ranges: Displays your data according to the ranges you set. Ranges are shaded with colors and/or patterns. Choose from templates displayed as shaded lines, points, or regions. Ranged thematic maps allow you to illustrate data values across points, lines, and regions. They are used to show a relationship between the data values and geographical area (e.g. sales figures, household income) or to present ratio information such as population density (population divided by area). Ratio information can be shown in other types of thematic maps when you choose Expression in Step 2.
    • Bar Charts: Displays a bar chart of your thematic variables for each record in your table. Use bar charts to analyze multiple variables per record on the map. Make comparisons between the size of the bars in each chart to obtain information about a record in the table set, or compare one bar in all the bar charts to draw conclusions about a variable across all of the records, or compare the height of the bar charts to obtain information about the entire table. To indicate a negative value in a bar chart, bars extend in the direction opposite to the chart's orientation. Negative values do not display in stacked bar charts. 
    • Pie Charts: Displays a pie chart of your thematic variables for each record in your table. Pie charts are multi-variable. Use pie charts on the map to analyze more than one variable at a time. You can compare the size of the pie wedges in each chart to obtain information about a record in the table, or compare one pie wedge in all of the pie charts to draw conclusions about a variable across all the records or compare the diameter of the pie charts to obtain information about the entire data set. 
    • Graduated: Displays a symbol for each record in your table, the size of which is directly proportional to your data values. A graduated symbol map shows data points with specific numerical values. It is useful for illustrating quantitative information, such as high-to-low rankings. The size of the symbols is proportional to the data values of the points. Points that have larger data values appear larger, and points that have smaller data values appear smaller. 
    • Dot Density: Displays the data values as dots on your map, where each dot is equal to a number, and the total number of dots in a region is proportional to the data value for that region. A dot density map allows you to examine raw counts of data (e.g. population). Each dot represents a number of units. That number, multiplied by the total number of dots in the region, equals the data value for that region. 
    • Individual: Shades records according to individual data values. Individual value templates are multi-variable. Choose from shaded lines, points, or regions. A thematic map that draws map objects according to individual values is useful when you want to emphasize categorical differences in the data rather than show quantitative information (e.g. types of stores in a given area, zoning classifications in a given area etc.). 
    • Grid: Grid mapping displays data as continuous color gradations across the map. This type of thematic is produced by an interpolation of point data from the source table. A grid file is generated from the data interpolation and displayed as a raster image in a Map window. 

    Instead of using a Grid thematic map type, I'd recommend using one of the many Create Raster methods you can find in the Create Raster dropdown on the Raster tab. This gives you far more control over the result. But this is a topic for another article. This feature requires MapInfo Pro Advanced.

    Once you have selected the Thematic Template you want to use, you click the Next > button to move to the next step.
    In the Create Thematic Map - Step 2 of 3 dialog you must select the table and column you want to create a thematic map for. The list of tables only consists of the layers in your active map window. The list of columns may also be limited depending on the type of thematic map you picked in the first dialog.
    You can also pick Expression from the Field list and build an expression for your thematic map in the Expression dialog. In the example below, I have calculated the population density for my ranged thematic map by dividing the population by the area of the boundaries in square kilometers.
    Step two can also present you with a dialog allowing you to select multiple columns. This is the case for the Bar Charts and Pie Charts.
    When you have selected the table and column or expression to use, click on the Next > button to move on to the third and last step.
    In the final dialog, Create Thematic Map - Step 3 of 3, you can change the final appearance of your thematic map. Again, the options may differ depending on the thematic map type.
    At the top of the dialog, you can see a preview of your thematic map. You can use the button on the right to modify the Ranges, the Styles, and the Legend of your thematic map.
    Under the Preview area, some options allow you to control the legend. You can set the Number of Columns and the Legend Label Order.
    At the bottom of the dialog, you can associate the thematic map with the table. Read more in this article: MapInfo Monday: Default Theme for Tables.
    And finally, you can save the current thematic map into a new template. This allows you to store the settings from your current thematic map for reuse.
    Click OK to see your thematic map in your map window.

    Modifying your Thematic Map

    You often want to modify your thematic map a bit after creating it. That's also quite easy in MapInfo Pro.
    The first thing you notice is the name of the thematic layer in the Layer List. You can however rename this similar to a normal layer.
    Right-click on the thematic layer and then click on Rename Layer. You can also use F2 after selecting the layer in the Layer List.
    You can now enter a more friendly name for your thematic layer. Hit the Enter key to apply the new layer name. If you click on the red cross, the custom friendly name will get removed and the original thematic layer name will appear.
    You also have full control over the actual thematic layer. If you select a thematic layer from the Layer List, the Theme tab will appear in the ribbon.
    From the Theme tab, you can control and change the thematic layer.
    Use the Field dropdown to change the attribute used in your thematic map. This allows you, as an example, to quickly switch between population counts from different years using the same thematic layer.
    The Method dropdown allows you to switch to a different Range Calculation Method with a single click.
    You can also modify the Range Count and the Value for Rounding the ranges.
    The Color Palettes dropdown allows you to switch between color palettes designed by ColorBrewer.
    Consider this a very quick introduction to creating thematic maps. You can find more details in the MapInfo Pro Help and documentation either locally or in the Precisely Help Center. Have a look at Home of #MapInfoMonday under Working with Thematic Maps for more articles on this topic.
    What type of thematic maps are you mostly using in MapInfo Pro?

    Peter Horsbøll Møller
    Principal Presales Consultant | Distinguished Engineer
    Precisely | Trust in Data