Last week, we kicked off Black History Month with a post about the father of the modern blood bank, Charles Drew. This week, we are turning our attention to the woman who programmed the mathematical model that made GPS possible, Gladys West. In 1956, West was hired as a mathematician for the Navy—one of only four Black employees at the Naval Proving Ground in Dahlgren, Virginia—where she worked as a “human computer,” making calculations based on astronomical data. By the mid-1970s, as part of the Seasat project, West was programming the new IBM computer with specialized algorithms to model Earth. Her incredibly accurate and precise geodetic Earth model is the fundamental basis for GPS.
West was born in rural Dinwiddie County, Virginia in 1930. Her parents were sharecroppers and factory workers. Growing up, West worked hard at her education, determined to escape her rural community. As a result of her hard work, she graduated from high school as valedictorian and got a scholarship for Virginia State University (VSU). West graduated from VSU with a degree in mathematics and returned to earn a master’s in 1955. After earning her master’s degree, she was hired by the Naval Proving Ground to be a “human computer”—a position that involved making calculations based on satellite data.
In the early days, all the math was written out by hand. “We would come in and sit at our desks and we would logic away, go through all the steps anyone would have to do to solve the mathematical problem,” West explained. But later on, she transitioned to programming a massive IBM Stretch computer with complex algorithms to make even more refined calculations. When she started at the Naval Proving Ground, West was one of only four other Black employees, but she didn’t let that discourage her. As a government employee, she wasn’t allowed to participate in any of the ongoing Civil Rights protests, but she hoped her work would speak for itself. “We tried to do our part by being a role model as a Black person: be respectful, do your work, and contribute while all this is going on,” West explained.
The first project West worked on at the Naval Proving Ground involved calculating the regularity of Pluto’s orbit with respect to Neptune’s. Neptune and Pluto have 3:2 orbital resonance, meaning that Neptune completes three orbits of the sun for Pluto’s every two orbits. This orbital resonance is critical to the stability of the planets. Most planetary orbits aren’t actually circular, they are elliptical—a somewhat stretched-out circle. Pluto’s elliptical orbit means that it crosses over Neptune’s orbit, so Pluto is actually closer to the Sun for about 20 years of its 248-year orbit. These orbits would be completely unstable if they brought Neptune and Pluto close enough together to gravitationally interact. But because of their orbital resonance, Pluto and Neptune never come within 93 million miles of each other (approximately the average distance between the Earth and the Sun). West worked on the team tasked with confirming this orbital resonance using astronomical data and over 5 billion calculations. The project was a success, earning a group achievement award in 1964, and West was made the project manager for a new endeavor known as the Seasat radar altimetry project.
The purpose of the Seasat project was to develop algorithms that would help Earth-orbiting satellites accurately map the Earth. The Earth is not really a sphere—even if you ignore the small irregularities like the mountains and oceans. Earth is really an ellipsoid—a sort of potato-like shape—that is flatter at the poles and wider at the equator. This phenomenon arises because of the centrifugal “force”—the artificial force we talked about last week that comes from the combination of rotational inertia and an inward force. Gravity pulls on objects equally in every direction, pulling them towards the center of gravity. If Earth was motionless, gravity would pull the crust into a spherical shape. But because the planet is spinning, the rotational inertia creates a centrifugal force that pulls the crust outwards as it gets further from the axis of rotation, creating the slightly potato-y shape.
So, the Earth should be accurately modeled by an ellipsoid that takes the centrifugal force into account, right? Not quite. Firstly, there are many irregularities in the Earth’s crust that can actually change the strength of gravity at different points. The strength of gravity decreases as you move farther from the center, so variations in the thickness of the crust can impact the strength of gravity. Gravity is weaker on the summit of Mount Everest than it is at sea level (fun fact, this is part of the reason why air pressure decreases at high altitudes). Additionally, the thickness of the crust is always changing over long and short timespans through geological processes and sudden weather events.
While the minute changes in altitude and gravity are mostly imperceivable on Earth, they make the job of a GPS satellite significantly harder. The purpose of the Seasat project, therefore, was to create computer algorithms that would allow satellites to map out the shape of the Earth and the changes in gravity. These algorithms had to be flexible enough to adapt to both subtle and sudden changes in the Earth’s geometry and also precise enough to enable pinpoint accuracy. West and her team spent much of the ’70s and ’80s developing and perfecting mathematical models and algorithms that could help satellites form these detailed maps.
While working on the Seasat project, West also completed a second master’s degree in public administration from the University of Oklahoma. She retired in 1998, after 42 years at the Naval Proving Ground, and suffered a stroke only five months later. Despite suffering losses in her hearing, vision, balance, and mobility, West refused to slow down. “All of a sudden,” she remembers, “these words came into my head: ‘You can’t stay in the bed, you’ve got to get up from here and get your Ph.D.’” Despite also fighting breast cancer in 2011, West earned a Ph.D. in public administration from Virginia Tech in 2018. Despite her central role in the development of GPS, West wasn’t publicly recognized for her contribution until 2018, when she received a commendation from the Virginia State Senate and was inducted into the Air Force Space and Missile Pioneers Hall of Fame. Today at 91, she continues working and mentoring young scientists and mathematicians. Despite her role in its development, West doesn’t use GPS, still preferring to use a paper map.
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