USA Population Change

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Why We Love It

We love how color and 3D shading work together to tell the story of US population changes from 2000 to 2010. Declining counties show up in red and shrink into the map. Growing counties pop in green and literally burst from the screen. As a bonus, you can zoom into a city to reveal more spatial details and discover changes in a particular neighbourhood.

Why It Works

What really makes this map useful (and smart) is the 3D shading that compares nearby places using relative height. 3D especially showcases meaningful and even subtle differences within each color. For example, red simply tells us that places are shrinking in population, but shading gives us relative-depth cues to indicate wide differences in losses within that category.

Important Steps

You will need population data for two different time periods such as 2000 and 2010.

Map the data using a diverging colour scheme (known in ArcGIS Online as “above and below”), and make the middle colour neutral, centred on 0 or “no change.”

To learn how to add the shadow effect, check out GitHub to find a Python tool that processes your data.

Run the tool to create 3D effects.

Evaluate the results in ArcMap or ArcGIS Pro.

Publish as a tiled map service to ArcGIS Online.

Requirements

Data

You need numerical data--it could be income, housing prices, life expectancy, anything that shows change over time. Maps like this work best with data that is a rate, ratio, percent, index, or average, and changes over time.

Analysis

Think about how to show growth and decline in population. Here, zero growth is a neutral colour and growth rates are shaded in diverging colours. The Python tool analyses growth rates to determine height and shading for each feature.

Time

The first time you do this it will take about one day for setup, one day for processing, and one day for caching.

Above and Below

Tips

Use an above-and-below colour sequence when you have a meaningful midpoint in your data that you want to emphasize, such as zero or an average.

Adding Shadows

Tips

When adding shadows, it looks more natural if you place the light source in the upper left, at the 10 or 11 o’clock position.

Map Author

Wesley Jones

Wesley Jones

Mapmaker, mapmaker, make me a map. I am a geographer and mapmaker. I like illustrating and writing. I also enjoy the sport of curling.

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