Kristine Larson was awarded the 2020 Charles A. Whitten Medal at the AGU Fall Meeting Honors Ceremony. The medal is for “her innovative applications of GPS geodesy to problems in environmental sensing, water cycle, geodetic seismology, and crustal dynamics.”
Kristine Larson is among the great innovators in geodesy. Whitten would be impressed and pleased to see the revolutionary applications she has invented or advanced, many of which were unimaginable at the time of Whitten’s 1994 death. Her innovative use of kinematic GPS and ground multipath reflectometry has led to the establishment of two new, distinctive areas of study: Global Positioning System (GPS) seismology and the use of GPS for environmental sensing.
Dr. Larson began her career using GPS geodesy for the measurement of crustal motions from local to global scales. In the late 1990s, she applied high-rate GPS positioning to study more dynamic ground motion, starting with deformation associated with Kīlauea Volcano. Subsequently, she advanced GPS techniques for investigation of earthquake ground motion, including a groundbreaking 2003 Science paper demonstrating that surface waves from the 2002 Denali Fault earthquake could be measured faithfully across all of North America. In this and later papers, she and her coauthors demonstrated that these GPS ground motion records contain unique seismological information, thereby establishing GPS as a tool that complements classical seismic observations.
Dr. Larson’s work in kinematic GPS led her to an intensive study of signal multipath and to her revolutionary application of GPS to many kinds of environmental sensing. She recognized that multipath was not just an annoying source of error to be removed but also a signal that contained information about the environment around the GPS antenna. She and her coworkers then devised simple but clever ways to extract quantitative information from the multipath signal. As a result, she has turned GPS sites into tide gauges, snow depth meters, permafrost sensors, glacier ablation meters, soil moisture meters, and vegetation water content meters, all validated against ground truth or independent data. Her team’s soil moisture products have further been used as validation for space-based remote sensing. Dr. Larson’s work in environmental sensing created a new range of applications of GPS geodesy. These advances and others are detailed in her recent review paper, “Unanticipated Uses of the Global Positioning System,” which I recommend all geodesists read. Her dual quest to understand both the behavior of the dynamic Earth system and also the intricacies of modern geodetic observing systems will inspire our field for many years.
—Jeff Freymueller, Michigan State University, East Lansing
First and foremost, I want to thank AGU, the Whitten Medal selection committee, the nominators, and my colleagues for this honor.
I had gone to college expecting to become an engineer—and soon frightened my family by initially choosing to major in history of science. How then did I end up measuring plate motions with GPS? I was first introduced to geophysics by my thermodynamics professor, James Rice; I was also inspired to become a geophysicist by the Harvard Seismology Group. I came home to San Diego for graduate school in 1985 and, thanks to Duncan Agnew, became involved with one of the first GPS experiments to measure crustal deformation. At some point I was asked to drive a TI-4100 to Los Angeles, which serendipitously led to both a NASA fellowship and a long-term research affiliation with the Jet Propulsion Laboratory.
When I graduated from Scripps in 1990, Earth science departments still hadn’t decided what to think of so-called GPS people, so I took a position in an aerospace engineering department. Colorado has been my home these last 30 years. My colleagues in Boulder have inspired the interdisciplinary GPS applications cited by Jeff Freymueller. Perhaps in some way working in geophysics while being surrounded by engineers has allowed me to successfully blur the line between those fields. I also had the good fortune to learn from colleagues at the U.S. Geological Survey (USGS) Hawaiian Volcano Observatory, Stanford University, the USGS Earthquake Program, the Earthquake Research Institute in Tokyo, the Onsala Space Observatory, and GeoForschungsZentrum in Potsdam while on sabbatical.
Growing up in the 1970s, I don’t remember anyone encouraging girls to pursue research careers in science or engineering. At the same time, my parents and grandparents never told me I couldn’t do something because I was a girl. Not ever. After I moved to Boulder I met my husband, George Rosborough, who has also supported my career throughout. I will always be grateful to him and our son, Radon.
Sometimes I am asked by people how I chose to work on all these nontraditional applications of GPS. I recently found this quote by David Blackwell, and I think he has summarized my views perfectly: “Don’t worry about the overall importance of the problem; work on it if it looks interesting. I think there’s a sufficient correlation between interest and importance.”
—Kristine M. Larson, University of Colorado Boulder