Ah maps. It’s all about encoding data into colors and stuff. But does it have to stop there? Why not get a bit more literal? Here’s how to make a thematic map of low values and high values look like an elevation map with low areas and high areas. Low and high looks low and high! Get it?
Here’s a rundown for the video-averse among you…
1. Find a grand and glorious polygon layer with some attribute that you want to map. In this example I’ve chosen Life Expectancy from the 2021 County Health Rankings which I added via Living Atlas.
![Life expectancy data from Living Atlas Life expectancy data from Living Atlas](https://www.esri.com/arcgis-blog/wp-content/uploads/2022/08/1CountyHealthData.jpg)
2. Duplicate this layer as many times as you want to want to have range breaks, and apply a filter to each copied layer so that it shows a specific range of the data. I ended up with five separate layers, each showing a five-year slice of life expectancy. Order the layers so that the highest value layer is on the top of the list.
![Layer duplicated into multiple layers, each with a filter showing a specific slice of data. Layer duplicated into multiple layers, each with a filter showing a specific slice of data.](https://www.esri.com/arcgis-blog/wp-content/uploads/2022/08/2SeparateRangeLayers.jpg)
3. Give each layer a gray color so that together, they look like a grayscale map. Light gray for the highest values to dark gray for the lowest values. Apply a drop shadow effect to each layer.
![Discrete layers are given a shade of gray and a drop shadow. Discrete layers are given a shade of gray and a drop shadow.](https://www.esri.com/arcgis-blog/wp-content/uploads/2022/08/3ColorAndShadow.jpg)
4. Create a group and add all the layers to this group, keeping them in descending order. Then, with the group selected, apply an overlay blend mode (my favorite blend mode).
![An overlay blend mode on the layer group creates a sense of light and shadow on the underlying imagery. An overlay blend mode on the layer group creates a sense of light and shadow on the underlying imagery.](https://www.esri.com/arcgis-blog/wp-content/uploads/2022/08/4OverlayBlend.jpg)
Overlay applies the light and dark grays of the layers (and their drop shadows) as tones to the underlying imagery, giving them a sense of illumination and depth. The lighter areas appear to be high plateaus and the lower areas are basins. It’s a landscape of low and high elevation driven by the low and high values of the thematic data.
![Completed life expectancy map, shown as elevation. Completed life expectancy map, shown as elevation.](https://www.esri.com/arcgis-blog/wp-content/uploads/2022/08/5Complete.jpg)
If you’d like to have a closer look at the example I’ve made here, you can fire up this web map. I’ve added labels for the life expectancy data, so there’s a bit more context when you zoom in. This is a fun one and pretty easy. Give it a shot with some choropleth maps you have laying around and see if it gives them a new sense of interest and intrigue.
Love, John
Article Discussion: