Rainbow Ghost Planes

After the Soviets launched Sputnik in 1957, the human viewpoint of Earth radically shifted. No longer were we mere stargazers, now we could watch what happened at home from a lofty viewpoint. Since the first satellite hit space, we have enhanced our abilities to gaze downward to astonishing levels. Governments and militaries can watch minute areas in real-time, while the average citizen has access to sophisticated renderings of every inch of the planet on machines we can tote in pockets. Every month, the newsletter employs Google Earth to zoom into the topics we explore, aiming to turn abstract articles into concrete locations.

These mapping tools are fantastic for the enterprising orophile. With ease, we can trek to the top of Everest or Denali, virtually reclimb our favorite mountain, or browse for unknown gems.

But, our planet isn’t only populated by inanimate objects. Critters of all shapes and sizes ambulate across the surface. Human-crafted machines, such as automobiles and airplanes zoom around. Check out your house and you just might catch your car parked in the driveway. Pan around the planet and, if you get lucky, you might even spot a plane in the air. Though Google has algorithms to delete aircraft from the long-term model, every now and then, one makes it temporarily to the web. You might even see a top-secret military craft!

And, unlike your parked car, the airplanes often look a bit strange, something akin to rainbow ghost planes.

What’s going on with these chromatic specters?

The answer arrives thanks to how the satellite gathers imagery. We learned that light colors are additive and that the human eye parses all hues through a combination of red, blue, and green. In many cameras, such as the ubiquitous phone camera, the primary colors register on the sensor at the same time. These satellites, however, have a lot of ground to cover and strive for the utmost accuracy. So, instead of taking one snap of all the colors at once, the satellites run scans of the individual colors. Think of a scanner or a photocopier, as the light wand moves across an area. This method allows for the full resolution of the sensor to be dedicated to each individual color, which is then produced as a high-quality composite.

This method works wonders on stationary objects. Scientists have even accounted for the movement of the satellites in their algorithms. However, when an object moves at a decent clip, things get a bit wonky. By the time one of the colors completes a scan, the airplane has moved slightly across the globe. When the second color hits the craft, it’s a bit farther along. The result is a staggered rainbow scan. Instead of composite clarity, we get apparitional translucence.

Sometimes, the images present an even odder effect than the rainbow ghosts:

The doppelganger phenomenon above is likely the result of a few other things happening in the imagery programs. In addition to the red, green, and blue scans, the satellite also takes a monochrome snap. In the photo above, that’s the white plane. The algorithms take the bones of the monochromatic image and stitch the rich color data on top to, usually, craft a nice object. However, because the satellite and the plane are in motion, the parallax effect can cause the object to “jump.” Though the satellite is programmed to take its movement into account, Google Earth is not interested in displaying airlines, so two moving objects create some chaos.

The parallax effect deals with perspective and is one of the main ways our binocular vision creates depth perception. Objects viewed at angles can appear to be in different spots, depending on one’s positioning. Scientists employ parallax to measure the distance to stars by waiting until the planet is on different sides of the Sun to view the giant balls of gas.

Though modern satellites employ the multi-color scanning strategy, the idea is actually old technology.

Some of the earliest color photographs were created using a similar stitching method before we even possessed the chemical ability to (effectively) capture colors on film. In 1855, Scottish physicist James Clerk Maxwell proposed the three-color method, which would later be utilized by some of the biggest photographers of the late 19th century. The method entailed taking a normal black-and-white photo through three filters: red, green, and blue. Through subject discipline and photographer skill, the three images could be superimposed and projected through the filters onto a screen. The outcome must have seemed to be magic at the time: a fully colorized snapshot. Thanks to the additive property of light, photographers could produce color images without the ability to capture colors with their film.

Among the wizards of the era was Sergey Prokudin-Gorsky, who created some stunning work. As you can see from his photos, the problem that plagues modern satellites was an issue in the 1800s, too. Stationary objects look great – and sometimes keeping people still through three protracted exposures was difficult – but it’s hard to hold some things motionless.

Prokudin-Gorsky lived to see the advent of airplanes but he probably could never have conceived of the idea of satellites producing the rainbow effect from space.

If you ever encounter a plane on a satellite image, you might want to snap a screenshot. They appear ghostly in the imagery and, like geists, they won’t last long. Engineers who discover a plane on the map send them to the rainbow ether.