ArcGIS Living Atlas

A First Glimpse into the Future of Population Data: Part 5

In the first four parts of this series, we’ve introduced a collection of multidimensional layers featuring WorldPop’s gridded population estimates, shown how to get started using these layers, and shared an example where these layers were applied to better understand women’s access to health services in Ghana.

Here in Part 5, we are sharing our response to the most common request we’ve received regarding WorldPop layers. Within a few weeks of publishing the layers in November of 2021, we received several requests for a “fast-drawing cartographic version”. These requests included that such layers needed to integrate with basemaps and work well with the new layer blend modes and effects.

To meet these needs, we created two new layers using the 2020 slice of WorldPop’s Population Density 100-m layer:

How to Use these Layers

The easiest way is to use these layers with 75 to 85% transparency with the light gray canvas map:

WorldPop Carto Layer 75% Transparency Example
Example: Light gray canvas base map (left, and on the right using WorldPop Carto Layers with 75% Transparency

Tip: Move one or both of the footprint layers into the base map.

Another option is to use the Composite Blend Modes with a polygon layer to better focus maps that should highlight population-based phenomena. Here we applied this idea to the COVID-19 Trends Countries Layer:

 

Apply Composite Blend Mode with WorldPop Layers
Example of using Composite Blend Modes to update the solid color map (left) to focus Covid-19 data on populated areas (right).

To make this above map, we used the following drawing order of layers in our webmap’s table of contents:

  1. Urban Density Footprint in 2020 (Destination Over blend mode)
  2. Human Geography Detail layer (75% transparency; this adds the gray background and labels)
  3. Populated Footprint in 2020 (Destination In blend mode and 75% transparency)
  4. COVID-19 Trends for Countries
  5. Basemap: Light Gray Canvas

 

Layer order for gridded population in destination blend modes
Layer order for using destination blend modes with populated footprint and urban density footprint layers.

There many other ways to mix these layers into your maps using blend modes – have some fun experimenting. Check out these blogs that share more about using the blend modes:

How we Made these Layers

The item page descriptions for the populated footprint and urban density footprint layers provide the steps we used to create each layer.  The processing for both layers included reclassifying the data to 1-bit integer rasters, which makes them very efficient to draw. We tested using an 8-bit image with percentile density values and found it drew more than four times slower. That made it easy for us to choose the option of two 1-bit layers.

How we Hosted these Layers

We took advantage of a relatively new capability:  ArcGIS Image for ArcGIS Online.  All we needed to do was create the 1-bit TIFF files of each footprint of population and then use ArcGIS Online to upload and tile them.

About the author

I am Chief Cartographer at Esri, and manage the Cartographic Projects Group on the Content Team. I have been with Esri in Software Products since 1994. I am currently the author of Esri's Ecological Land Unit services, global ecological content, and the World Population Estimate Services. Contact me at cfrye@esri.com with questions or feedback.

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