For his 50th birthday, John Parr Snyder’s wife bought him a special gift: a ticket to “The Changing World of Geodetic Science,” a cartography convention in Columbus, Ohio. Geodesy, an esoteric branch of geography studying the shape of the earth, had been one of Snyder’s lifelong hobbies. As a keynote, the 1976 conference featured a speech from Alden Partridge Colvocoresses, decorated World War II hero and head of the USGS’s national mapping program.

Snyder went home inspired. He had a day job, but in less than four months, working alone, at night, without pay, and using a calculator that stored his work on magnetic tapes, he solved the problem of making maps from space.

When NASA launched the LandSat program (originally called the Earth Resources Technology Satellite), making maps wasn’t a priority. But many engineers soon saw how valuable it would be to assign geographic coordinates to high-resolution images. Colvocoresses, no mapping slouch, came up with a theoretical solution in 1973, which he called the Space-Oblique Mercator projection.



It was based on Geraldus Mercator’s 1569 projection, because it preserved the angles of Earth’s surface features in relation to one another (a property called conformality). Unlike the original Mercator, which used the equator as a line of zero distortion, Colvocoresses decided that the line of zero distortion would be the path along the earth’s surface directly below LandSat’s camera. Because LandSat’s camera only captured a 100-nautical-mile-wide swath, distortion would be minimal.

Mapping from space isn’t as easy as matching up photo features to the cartesian graticule. Even though the images were two-dimensional, they were of a curved surface, which means they needed to be geometrically adjusted—projected—as flat areas.

Colvocoresses turned the Space-Oblique Marcator’s basic structure over to his team of geographers. “They didn’t think it would be a big problem to project the photos and make them into maps,” said John Hessler, a geographer at the Library of Congress.

Thing is, there are no small problems in space, and LandSat’s mappers had four. Projections are essentially views of the Earth from imaginary, elevated viewpoints, and people have been making them for 2,000 years. However, nobody had ever considered that if they were going to actually make a map from an actual elevated viewpoint, they’d have to account not only for the platform moving (in orbit), but also the earth rotating below. But the Earth doesn’t just spin, it has a little bit of a wobble, too. And then there’s gravity, which doesn’t pull uniformly across the earth’s surface, but is stronger is some places, weaker in others (because the Earth is denser in some areas and less dense in others). All these things affect the satellite’s position and altitude relative to the Earth, and all of them need to be considered before you make a map from a satellite.

When years went by without a solution to these problems, Colvocoresses turned to outside help, including John L. Junkins, an engineer at Texas A&M. Junkins specialized in telemetry—tracking moving objects—and was a good bet for figuring out how all those motions could fit into a mappable geometric equation.

But Colvocoresses was a former Army strategist (who helped prep for D-Day), and he knew that a battle this tough should be fought on multiple fronts. He put his plea to the masses, and in 1976, at Ohio State University, at the Fawcett Center for Tomorrow, at the geodetic conference, that plea reached the ears of lifelong map addict John Snyder.

Snyder took a different tack than Junkins and the USGS scientists. They were trying to create a comprehensive framework using Newtonian physics that could be used to predict the ground track of any orbiting body onto Earth. Snyder didn’t care about trying to predict all the motions, he was only concerned with the ones that mattered. “His equations didn’t tell you anything about how the satellite was moving,” said Hessler. “He just looked at the central path of the satellite and calculated how it would relate to lines of latitude and longitude.”

Hessler, the Library of Congress geographer, calls Snyder a cartographic prodigy. His high school notebooks are full of drawings, notes, and equations all about map projections. Though he went to school for, and worked most of his adult life as, a chemical engineer, he wrote several books about mapping. Shortly before the Ohio convention, he had bought himself a TI-59 programmable calculator. (Snyder had quit trying to create map equations years before, because the equations got too difficult for him to do on paper.)

In his later years, he became a master of herding geographic distortion, so he could preserve the shapes and sizes of the features that he was wanted in focus. One example of this is the GS50, the only projection where you can see all 50 states—including Alaska and Hawai’i—on a single, seamless map with minimal distortion. A few years before he died in 1997, he published what many consider to be the bible of map projections: a surprisingly readable volume called Flattening the Earth.

Snyder was too anxious to send his calculations directly to the USGS, so he asked Waldo Tobler, a geographer at the University of California in Santa Barbara, to review them first. Tobler saw that they would work, and forwarded them along to the Colvocoresses. The moment he saw it, the USGS mapper knew that Snyder’s work was the key to making Space-Oblique Mercator work. He asked if he wanted to move from New Jersey to Virginia, and become a professional cartographer with the USGS. And John Parr Snyder, who had been obsessed with maps since he was a boy, accepted without hesitation.