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Lights On, Lights Out

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Why we love it

What if you could distill human movement, ambition, and violence on our planet into one single picture? This story map accomplishes that. We love how it directly compares Earth at Night imagery from 2012 and 2016 to show new or extinguished nighttime illumination. We see an illustration of nighttime light’s dichotomous nature, its ability to reveal progress or tragedy. Notably, the map shows the light from recent electrification in rural northern India and, in contrast, the darkness brought on by cataclysmic civil war in Syria.

Why it works

Maps with a single binary theme, such as more or less, are understood easily and don’t require legends or other complex explanations. Using the Firefly aesthetic, this map maintains the sense of lights flickering on or off. The effect is actually a derived mathematical result of varying input values arranged in a raster grid. Desaturated imagery allows the data to jump off the screen, captures a sense of nighttime realism, and provides context without the need for many basemap labels.

Firefly basemap starter pack

Important steps

  • Download NASA map

    Download high-resolution 2012 and 2016 Earth at Night imagery from NASA.
    Download global map

  • Georeference and perform a minus function

    Georeference the imagery for spatial sentience, allowing for re-projection. Perform a Minus raster function on the 2012 and 2016 images to derive increased and decreased nighttime brightness.
    More about georeferencing tools
    More about the Minus function

  • Represent nighttime brightness with color

    Create a custom color scheme to brightly paint the pixels representing increased and decreased nighttime brightness, while assigning full transparency to midranges with unchanged nighttime brightness.
    Learn about color schemes

  • Add background and create colorized text title

    Add a dark, desaturated satellite imagery basemap for tone and context. Create a colorized text title that informs on the topic while providing dual service as a legend.
    Desaturated satellite imagery basemaps
    Create a colorized text title

  • Create an immersive experience

    In a Story Map Cascade, walk readers through the data, the phenomenon, interesting examples, and the process.
    Learn about Story Map Cascade
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Requirements

  • Data

    This map uses a series of eight high-resolution nighttime images, in JPEG format, from the Earth at Night Collection by NASA’s Visible Earth team, captured via satellite and processed to show areas of nighttime illumination in 2012 and again, four years later, in 2016.
    Earth at Night Collection: Flat Maps

  • Analysis

    Analysis took a matter of seconds. The Minus raster function quickly compared historic imagery for differences in pixel value. A cursory visual examination proved the results to be fruitful and ready for thematic symbology.
    Minus raster function

  • Time

    This map was generated in a matter of two hours. Most of the time was spent in refining the custom color scheme used to illustrate increased and decreased brightness.
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Tips and tricks

  • Consider accessible colors

    This map is difficult for readers with colorblindness. A second version was created to overcome this.
    Second version for color blindness

  • Don’t map everything

    Pixels for places without change in light appear transparent to reveal only the reference imagery.
    Learn about color

  • Don’t go with traditional legends

    Instead of a traditional legend, provide information using text blocks, a descriptive title, and a font color that matches the symbology.
    Add and modify graphics and text
    Add text symbols
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Resources

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Headshot of John Nelson, map author

Map Author

John Nelson

I have way too much fun looking for ways to understand and visually present data, engage others, and write about it. Otherwise, I’m chasing around toddlers and wrangling chickens. Life is good.

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If you liked this map, check out these other Maps We Love that explore similar topics.

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