Robert Simmon is the creator of the famous blue marble image of a spherical earth. This is a short video with audio from an interview with Robert Simmon explaining how he created that famous image from composites. Why do we have to take multiple high altitude photos of Earth and piece them together? Why can’t we just take one single shot of Earth from “space”?
October 6th, 2011 by Robert Simmon
My role is to make imagery from Earth sciences data
Here’s how I did it.
In 2002 my colleague Reto Stöckli (now back in Switzerland) was working on a global map of the Earth that was going to blow away all previous examples. A new NASA satellite (Terra) was gathering the first color pictures of the entire Earth, and we wanted to showcase the imagery. Reto put together about 10,000 satellite scenes (each file over 300 MB) collected over 100 days, stripped out the clouds, and created a 43,200-pixel by 21,600-pixel map of the Earth in (this was the hard part, everything I did afterwards was just adding chrome).
Now that we had a source image, we needed to create something evocative, something that would show the potential of the imagery. To us, at least, the obvious choice was to render a few 3D views of the world as it would look from space
To make the Earth look realistic, or at least how I imagined the Earth would look, I needed to do some work. First of all, the satellite images weren’t usable over deep water (it collects data, but there’s no automated process to detect clouds and correct for the atmosphere), so I needed to add some color into the water. NASA measures chlorophyll in the ocean (a way of monitoring phytoplankton), so I grabbed a month’s worth of that data, colored it blue and green (I looked at individual satellite images to get a sense of what hues to use), and used that map for the ocean. I also had to add a stand-in for sea ice, since it’s impossible to measure chlorophyll beneath a few meters of snow and ice. At least that was simple–I just replaced missing data near the poles with white. In addition to the sea ice, I brightened and reduced the saturation of Antarctica, which was pasted into the original from a different dataset. The combined ocean color and ice look like this
Throw in a map of clouds stitched together from 200 satellite scenes, and a global topographic map to add some texture in the landscape, and I was ready to bring everything into my 3D software (Electric Image at the time). Wrapping a rectangular image onto a sphere and rendering out images was probably the simplest and fastest part of the entire process. It’s much easier to fine-tune an image with each component of the image rendered separately, so I made individual renders of the land and ocean, specular highlight, clouds, a couple day/night masks, and atmospheric haze (which I never did get quite right).
Compositing separate images into a convincing whole is (of course) easier said than done. Even with control of each layer in my image processing software (Photoshop) it took hours of tweaking and re-tweaking transparency, layer masks, hue, saturation, gaussian blur, and curves to get an image that looked like the picture I had in my head. Since it was before adjustment layers were introduced (with which I could have saved all the settings), I have no idea exactly what I did. Making the clouds appear opaque, while remaining white, rather than gray, was by far the hardest part. It was also tricky trying to get the atmosphere to appear most transparent in the center, and thicker and bluer near the edges. Looking at the Photoshop file, I’ve got two atmospheric layers and two cloud layers, each set to different levels of transparency, over a combined land and ocean layer, with sunglint (a specular highlight) off Baja California.
At the time, I had no idea the Blue Marble would be seen by so many people: it was just a way to show off some cool data. It’s based on the hard work of the literally thousands of scientists, engineers, programmers, admin staff, and others here at NASA
https://www.nasa.gov/people-of-nasa/goddard-people/robert-simmon-aka-mr-blue-marble/
Robert Simmon took “satellite” composites and created a flat map of the world which he then had to bend it into a spherical image. I’m honestly even skeptical that they used any even segmented images of Earth to make the famous blue marble, I feel like it is purely based off imagination and as Robert says himself speculation ^_^
