Seeing the Earth at Night with Daytime Eyes

Kilauea lava flow as seen by Landsat 8 at night on June 24, 2018.

You know that feeling of desperation you get when you walk into a darkened movie theater in the middle of a beautiful sunny day and you can’t see a darn thing?

Ohhh, I think I see the exit sign! But where the heck are the seats? WHY IS THIS TRAILER SO GLOOMY?!

Then you play chicken with your date. No, YOU pick our seats! And you proceed, hoping beyond hope that you don’t accidentally sit on someone’s jumbo Pibb Xtra (formerly known as Peppo, apparently).

Without getting into eyeball mechanics, you’re having trouble seeing because your eyes are primed for the blazing bright sun outside, not the dimly lit stadium seating you’re now stumbling through. You can see bright things—exit signs, the projection room, the gloomy trailer, some heel’s phone—but everything else looks black.

The same thing happens nearly every day as the NASA/USGS satellite, Landsat 8, continuously whips around the world. After scanning sunlit expanses, the satellite passes under the South Pole and ascends the latitudes into night, where it collects images by special request.

VIIRS is super at nighttime lights!

Unlike the VIIRS sensor, which is expertly calibrated to take images at night, Landsat 8’s “operational land imager” sees most clearly during the day (images collected with the satellite’s thermal sensor fare just fine at night, but that’s another — somewhat fuzzy — story). Landsat 8 does not see so well at night.

An exceptionally bright landscape like this comes across loud and clear, but…

A very bright Landsat 8 scene off the coast of Iceland.

When that camera passes under the South Pole and starts collecting those pre-requested nighttime images, many of them look this:

Night
Illustration of what a room looks like right after you extinguish a lamp from New Method of Geography and Mapping, 1901.

Night is dark—duh. And since the satellite only really does well imaging sunlit landscapes, it needs bright points in order to see. So when there’s nothing bright in the scene, it appears black—like the inside of your eyelids when you go to sleep, or a room where a light has just been put out (as in the illustration above).

But if there are bright landmarks in the scene, some pretty spectacular patterns emerge.

Shanghai

Shanghai, China as seen by Landsat 8 at night on October 11, 2015

In this picture of Shanghai at night from 2015, you can clearly make out the Huangpu River and several busy urban areas. You can also see Shanghai Stadium as a perfectly circular beacon to sports, visible from spaaaace.

Shanghai Stadium

Tokyo

Anyone who has ever visited Tokyo might have the city’s many billboards permanently seared into their retinas. It’s an exceptionally bright city.

And you can see that brightness at night, even with Landsat 8’s daytime eyes.

Tokyo, Japan as seen by Landsat 8 at night on December 28, 2016

From south to north, Shibuya, Shinjuku and Ikebukuro look like their own star clusters in the Tokyo galaxy. In the southwest corner of the image, strings of lights make up transportation routes, like the number 3 and 4 expressways and the Den-en-toshi Line. Tokyo Tower, The Park Hyatt Tokyo, train stations… and this block (for some reason) are all literal bright spots.

Light clusters clockwise from top left: Shinjuku, Tokyo Station and surrounding area, Roppongi and Shibuya

Looking closer at the brightest parts of this bright, bright city, the negative space jumps out nearly as much as the lights themselves. West to east, Yoyogi Park, Shinjuku Gyoen National Garden, The Akasaka Imperial Property and Chiyoda together form (with the exception of some well-lit tennis courts and a few other odds and ends) a dark backdrop to the shining urban neighborhoods of Tokyo.

London

London is like a cold dark dream sometimes. — Jean Rhys

Heh, yeah, sometimes. Yet even in the damp chill of a February night last year, London was shiny enough for a snapshot. If you know the geography of the city quite well, you might be able to pick out the Thames. But it’s much more likely that the first things that pop out to you are the uninterrupted lines of lights in the center of the city. Those are bits of Regent Street north and south of Piccadilly Circus (and The Mall a tad to the south running perpendicular).

London, England as seen by Landsat 8 at night on February 27, 2018.

Another thing that may strike you about this image (at least if you squint and scan it with the screen right up to your face) is the scattering of large blobs of remote radiance. Unsurprisingly, many of those are stadiums and pitches.

Amongst the brightest points are: Twickenham Rugby Ground; the “intensive use pitch” (good one, Google) at Meridian Sports & Social Club in Woolwich; Wembley Stadium; London Stadium (built for London Olympics); Sutcliffe Park Sports Centre; Emirates Stadium (where Arsenal plays) and Highbury Square (an apartment complex in the stadium where Arsenal used to play); Gasholder Park in King’s Cross; and the Sky Campus in Brentford.

These and other lighted landmarks each have a distinct shape and size. Here’s a close look at 100 of the brightest.

100 of the brightest landmarks in London on February 27, 2018

New York

Times Square in Manhattan outshines the boroughs in this image of New York from 2015, but you can also see Citi Field far off to the east: a bright green monument to fall baseball. It almost looks like you could grab a loupe and see a dinger in action, but—trust me—you can’t. I tried.

New York City as seen by Landsat 8 at night on September 21, 2015

Zoom! Enhance! A tighter look around Times Square and Manhattan shows many shiny spots. The Empire State Building, Citigroup Center Tower, The High Line and W. 14th St, and (for whatever reason) these buildings off the Westside Highway were all blazingly bright the night this image was taken.

I’ll Keep Looking

Using Landsat 8 to look at nighttime lights is nothing new. But I’m certain there are fun stories buried in this under-appreciated look at urban landscapes. Sure, most lights don’t register and the images can look horsey and pixelated, but what does shine reveals fascinating cityscapes with unique illuminated signatures. (Besides, wouldn’t you rather see just the exit sign in a dark movie theater than nothing at all?)

Postscript

Here’s one last image of Mexico City. But, if you’re so inclined, there are also many more to explore.

Mexico City on March 20, 2019

Cities are just one kind of feature you can find in these nighttime Landsat 8 images. Lava flows (as shown in the top image of this post) and oil and gas flares also pop.

What else can we all find?

Geographer