Purple Dot? Investigative Cartography

Got an Apple TV? Have you watched their screensavers and ever wondered what that purple dot in Wisconsin is?

Initial observation: 

One of the Apple TV Aerial video screensavers, “North America Aurora”, shows a VERY purple dot somewhere in Wisconsin as part of a night image from space:

Night image showing the purple dot

The purple dot

Unfortunately, simply asking the internet about the purple dot on the Apple TV screensaver is not enough to get you an answer (yet?).


WHAT is that purple dot? Inquiring minds want to know (but not enough to have figured it out months ago when it first bothered them)!

Equipment & Materials:


As the NightEarth maps and the Apple TV screensaver are looking at the Earth at different angles, we need to:

  1. identify major cities by pattern matching patterns/shapes of lights of cities and along highways, and
  2. determine where the point of interest (purple dot) is located relative the identified major cities.


Comparing the NightEarth maps to the Apple TV screensaver, we found that the purple dot seems to be located near the intersection of Wisconsin Highway 121 and Interstate 94, which corresponds to the town of Northfield.

Knowing that, a quick google search for “northfield WI purple light” brings up a Reddit post (“PSA: That Magic Purple Greenhouse is called Superior Fresh“) that gives us the answer; that purple light is apparently Superior Fresh, which was the largest aquaponics facility in the world when it opened in August of 2017.

This makes a lot of sense as LED grow lights are often red and blue (= purple), which is based on the absorption wavelengths of chlorophyll, but viewing plants under purple light can have drawbacks (even NASA added in green lights so plants looked more “food like” to folks growing them), and obviously, purple light leakage can make large growing operations blatantly obvious, even from orbit!


The purple dot visible from space, located in western Wisconsin, is the Superior Fresh Aquaponics facility!

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