Choropleth Map

This workflow aims to create a map of Seattle that shows different socioeconomic features by tract. This type of map is called a choropleth map, which uses colours to represent statistical information about a particular region, such as population density or income per person.

To use the workflow, download and run it on the KNIME Analytics Platform. For optimal performance using the Geospatial Analytics extension, make sure you are using version 4.7.4 or higher.

The input data has been saved in the workflow data area, simply execute the components "Read Dataset" to obtain the necessary data.

We have two datasets. The first one, "Consolidated Demographics Index for King County Census Tracts / demographic index area," is located on the top branch and provides socioeconomic information for King County, WA tracts.
The second dataset, "2020 Census Tracts - Seattle," is located on the bottom branch and contains the tracts boundaries of the city of Seattle.

To create our choropleth map, we gather data on the median household income and the percentage of people of colour (POC) by tract and calculate the population density per square kilometre using the tract polygon area.
We first converted the geometry column to an Equal Earth projection via the "Projection" node to calculate the area. This conversion resulted in a new " Projected " column with updated coordinate reference system information. The Math node was then used to obtain the population density per square kilometre for each Seattle tract.

We have generated a map that includes all the socioeconomic features we want to plot but also includes tracts from all over King County, WA. To limit the map to only the tracts in the city of Seattle, we utilized the "Clip" node. By applying a mask from the bottom dataset, we were able to clip the entire King County map and keep only the tracts within Seattle.

The output table is passed to a component containing different "Geospatial View Static" nodes to view geospatial data with various configurations. Each node has its title, colour scheme based on a distinct socioeconomic feature, and legend type. Take a closer look at the node configurations, with a particular emphasis on the legend settings, by opening the component.

The static view is helpful in this case because the choropleth map is usually intended to be viewed as a static image.

External resources

• 2020 Census Tracts - Seattle
• Choropleth Map example
• Consolidated Demographics Index for King County Census Tracts / demographic index area