AGU 100

Top 100 Advances in Geodesy

To celebrate the AGU Centennial, the Geodesy Section is recognizing compelling advances in geodesy in the last 100 years including:
• Science – research advances in understanding Earth and Earth processes
• Technology – advanced in instruments, field work, hardware and other technological endeavors
• Data – advances in computation, data analysis, data management, and software
• Education – advances in education (formal or informal) or education research
• Broader Impacts – advances in applied science, science management, community engagement, and societal benefits

Submissions accepted through the start of AGU 2019 Annual Meeting.
Please submit your advances via email to the AGU Geodesy Section Centennial Committee (Vicki Childers, Tim Dixon, and Linda Rowan) at geodesyadvances@unavco.org with subject heading "100 Advances in Geodesy".


1955: Gold showed mass redistribution on the surface or in the interior of Earth would result in a reorientation of the body w/respect to spin axis orientation. Subsequent studies of true polar wander advance understanding of Earth. Gold 1955, Sci Adv 67

1958: Triangulated deformation msts. on either side of faults - before & after earthquakes, along w/focal depths, to confirm the coincidence of seismically-detected eqs. & faults. Obs. of central tenet of elastic rebound theory, K. Kasahara 1958. Sci Adv 94

1970-1972: Used signal processing tools to extract an isostatic Green's Function (GF) from topographic and gravity data. Showed local isostasy, could be extracted from GFs. Dorman & Lewis 1970, Lewis & Dorman 1970, Dorman & Lewis 1972. Data Adv 65

1971+: Repeat microgravity used to measure aquifer specific yield and map aquifer storage changes. Montgomery, E. L. 1971, Determination of coefficient of storage by use of gravity measurements, Phd, Uni. Arizona; Pool & Eychaner, 1995. Data Adv 73

1977: Multibeam Echosounder - mapping seafloor. Developed for US Navy, then sci in 1970s. Multibeam data transformed our vision of processes acting on seafloor & of geomorphic features associated with mass-wasting & volcano-tectonic processes. Tech Adv 52

1978: Seasat, 1st Earth-orbiting satellite for remote sensing of Earth's oceans with 1st spaceborne synthetic-aperture radar (SAR). Demonstrated global monitoring of oceanic phenomena & determined requirements for ocean remote sensing. Tech Adv 68

1980-1991: Angular momentum changes in atmosphere balanced by equal & opposite changes in angular momentum of solid Earth. Rotation of Earth & other planets provide info abt atmos. & core. Hide et al. 1980; Hide&Dickey 1991. Sci Adv 53

1981: Computed luni-solar forced nutations of an elliptical, rotating, self-gravitating, elastic, hydrostatically prestressed & oceanless Earth. Corrected astrometric data for the nutation of Earth, so other effects can be studied. Wahr, 1981. Tech Adv 60

1984: Adoption of Fourier Transforms to Geoid Modeling. Recognized Stokes integral & TC integral as "convolution integrals" could transform to frequency domain so FT could solve integral fast & advanced geoid modeling. Sideris 1984, Schwarz et al. 1990, Data Adv 61

1984+: Formation & ongoing work of @UNAVCO by @NSF_GEO. Originally University NAVSTAR Consortium to share GPS receivers etc. to measure plate motion using nascent GPS constellation. UNAVCO, now non-profit to support research using geodesy. Broader Imp 79

1988: Defining the Characteristic Signal of Reflected GNSS Around an Antenna. Georgiadou & Kleusberg 1988, showed that interference patterns have a characteristic frequency that depends on the height of the antenna above the reflecting surface. Tech Adv 70

1988+: TANGO project, regional GPS experiment - European & North American, Azores Archipelago network, Described complex tectonics betw/North American, Eurasian & Nubian plates, Bastos et al. 1991; More than 20y of GPS obs now - increase precision. Sci Adv 96

1988-1990: Regional GPS campaign and collaboration to measure geodynamics of Central and South America called CASA UNO (25 orgs., 13 countries, 43 GPS receivers, 590 days of data). Kellogg & Dixon 1990. Sci Adv 98

1989-1992: Nascent GPS-based obs of regional geodynamics in California. Helped define plate tectonics, fault processes advance techniques etc... Dong & Bock, 1989 & Larsen & Reilinger, 1992. Sci Adv 58

1990- 2002: Steadiness of plate motion on different timescales observed by geodesy. Plate motions over tens to millions of yrs similar. Similarity shows viscous asthenosphere damps out episodic motions. Smith etal. 1990, Gordon&Stein1992, Sella etal. 2002 Sci Adv 93

1990: Measuring coseismic slip during the 1989 Loma Prieta, California earthquake with GPS. Lisowski et al., 1990. Sci Adv 78

1991: Alaska Satellite Facility at Geophysical Institute at the University of Alaska Fairbanks. Mission to make remote-sensing data accessible for polar processes, wetlands, glaciers, sea ice, climate change, permafrost, & flooding. Broad Imp Adv 76

1993: Differential interferometric radar has widen our eyes to see our dynamic Earth. Including a mapping of the 1992 Landers earthquake surface displacements, Massonnet et al., 1993. Sci Adv 64

1993: Satellite radar interferometry to measure flow velocities & grounding-line positions of Rutford Glacier, Antarctica, advance tech. & understanding of ice stream dynamics; Goldstein et al. 1993. Sci Adv 100

1994: Determining crustal motion in central/east Mediterranean from campaign SLR msmts, showed west motion of Anatolian Block relative to Eurasia, Smith et al. 1994, Sci Adv 86

1994+:Global models (NUVEL-1, DeMets et al 1990 & NUVEL-1A, DeMets et al, 1994) describing geologically current motion btw 12 assumed-rigid plates by inverting data, such as ocean floor magnetic anomalies, transform faults & eq. slip vectors, over 3–5 MY. Sci Adv 83

1995+: Glacial isostatic adjustment (GIA) is large & measurable by space gravity & Global Positioning System (GPS) msmts can separate GIA from present-day ice-mass balance. James & Ivins 1995, Sci Adv 80

1995-1996: Estimation of plate motion from southern France to Turkey w/combination of SLR & GPS, shows a microplate in south Greece & the Aegean Sea, & sense of motion across North Anatolian fault. Noomen et al. 1996, Sci Adv 55

1995-1997: Early GPS campaigns provided obs. of geodynamics of the Mediterranean region, identifying plate processes, hazards & advances techniques. Straub & Kahle, 1995, Noomen et al. 1996, Reilinger et al. 1997. Sci Adv 95

1997-2001: Development of GNSS radio occultation technique to understand atmosphere, enhance weather models for a better atmospheric predictions. Kursinski et al. 1997, Hajj et al. 1998, Wickert et al. 2001. Tech Adv 82

1999: Geodesy shows difference btw plate boundary & intraplate earthquakes. At plate boundaries, GPS data show strain accumulating via earthquake cycle. GPS data for New Madrid seismic zone find no or little strain accumulating. Newman et al. 1999 Sci Adv 71

1999: The International VLBI Service for Geodesy & Astrometry (IVS) supports global Very Long Baseline Interferometry (VLBI) components. Advance reference frame, tectonic plates, gravity, length of day, atmospheric models, etc... Broad Imp Adv 81

2001: Measuring water loads with GNSS. van Dam et al. (2001) observed water loads in vertical component time series from nascent IGS network using models to quantify effects of groundwater, snowpack, & soil moisture. Tech Adv 66

2001: Spatially dense space geodetic obs. of interseismic def. as predictive tool for future eq. hazards. High-res. maps of surface velocities constrain slip rates, interseismc coupling, extent of seismic layer, stress accum.. Peltzer et al. 2001 Sci Adv 90

2002: Geodetic detection of extensive damage zones on major crustal faults reducing elastic moduli. Direct observational constraints on the extent of damage & the degree of softening of rocks made possible with InSAR. Fialko et al. 2002, Sci Adv 89

2002: Geodetic detection of the shallow coseismic slip deficit. Smaller amplitude of near-surface slip compared to slip in the middle of seismic layer, Simons et al. 2002. Sci Adv 92

2002: Widespread active volcanic deformation of remote central Andes volcanic arc documented using InSAR surveys, Pritchard and Simons, 2002. Sci Adv 75

2003 - 2004: Revelation of timescales of variability of ice streams and glaciers from minutes to millenia from geodetic and other data/modeling. Bindschadler et al., 2003, Scambos et al., 2004. Sci Adv 69

2004: Confirmation of Lense-Thirring Effect with Satellite Laser Ranging. Ciufolini & Pavlis 2004, confirmed twisting effect of spinning Earth on orbits of 2 satellites using Satellite Laser Ranging (SLR) data of Int. Laser Ranging Service. Sci Adv 57

2004: High Rate GPS Measurements of Earthquake Slip History. Ji et al. 2004, produced 1st eq slip history using high-rate GPS positioning records for 2003 Mw 6.5 San Simeon earthquake. High-rate GPS positions combined w/seismic & GPS static offsets. Sci Adv 62

2006: Gravitational effect of the pole tide (small ocean tide with an amplitude ~ 6 mm, only non-extraterrestrial effect) is easily detected by the superconducting gravimeter. H. Virtanen thesis, 2006. Tech Adv 87

2006: High-Rate GPS for Rapid Estimate of Earthquake Magnitude (7+). Blewitt et al. (2006) showed GPS data can rapid determine magnitude for Mw9.0 2004 Sumatra earthquake. Could lead to better, quicker tsunami warning, Sobolev et al. 2007. Tech Adv 56

2008: Measuring Soil Moisture with GNSS Reflections. GNSS-Interferometric Reflectometry soil moisture msmts, Larson et al. 2008, using satellite signal that reflects off ground. Provides info about hydrologic, climatic, & ecologic conditions. Tech Adv 63

2009: Investigation of the Chandler Wobble with 163 years of data from IERS using 2 digital filters & 2 transforms; found 3 phase reversals 1850, 1920, 2005 that slow wobble; Malkin & Miller 2009. Data Adv 84

2010: GPS data measures relative & absolute plate motion. Shows today's velocities of major tectonic plates agrees w/estimates from other geologic & geophysical data, DeMets et al., 2010. Sci Adv 91

2010: High-rate GPS Measurements of Slip Distribution for M8.8 Maule Earthquake. GPS measures > 5m horizontal & >1.7m vertical change, constrain rupture process. Delouis et al. 2010, Vigny et al. 2011. Sci Adv 51

2010: Measuring Vegetation Water Content with GNSS Reflections. Small et al. 2010 measured vegetation water content w/GNSS-Interferometric Reflectometry. Use changes in reflection amplitudes of the frequency. Tech Adv 54

2010: New Zealand’s network (GEONET) of 150+ cGPS sites records slow-slip events every 5 years with durations of 6 days to 1.5 years on Hikurangi Subduction Zone from decades of obs. Wallace & Beavan 2010. Sci Adv 99

2012: A Reconciled View of Ice Sheet Contrib. to Sea Level. Satellite altimetry, interferometry, & gravimetry data estimate mass balance of Earth’s polar ice sheets. Shepherd et al, 2012. Since 1992, ice sheets contributed 0.59 ± 0.20 mm/y. Sci Adv 59

2012: Discoveries of new volcanic deformation, InSAR obs. of surface def. due to Altiplano-Puna Magma Body, revealed conjugate pattern of uplift surrounded by broader region of subsidence - “Sombrero uplift”. Fialko&Pearse 2012, Henderson&Pritchard 2013. Sci Adv 85

2017: Dense postseismic GNSS data & models find sliver motion controlled by kinematic interplay betw megathrust & upper plate or fluids moving downdip, 2012 Mw7.6 Nicoya EQ, Hobbs et al. 2019 & Mexican SZ, Fasola et al., 2019 Sci Adv 88

2019: International network of geodetic Very Long Baseline Interferometry (VLBI) radio telescopes provide global reference frame for radar satellite data (SAR), can now measure global sea level etc. Parker et al, 2019. Tech Adv 97

Mars rovers, Spirit & Opportunity, traversed 50km+ at accuracy of 1.5/1000. The geodetic long-distance localization & planetary surface mapping achieved a tech advancement within deep space infrastructure. Arvidson et al., 2004, Tech Adv 72

Satellite Laser Ranging, SLR & Lunar Laser Ranging, LLR, use short-pulse lasers & optical receivers & timing electronics to measure distance from ground to satellites & moon. Measure positions, motions, orbits, gravity, orientation. Broader Imp. Adv 74

Two-thirds of the Chandler wobble caused by fluctuating pressure on the seabed, caused by changes in the circulation of the oceans caused by variations in temperature, salinity, and wind. Gross 2001. Sci Adv 77

Seasat.jpg
1978: Seasat, 1st Earth-orbiting satellite for remote sensing of Earth's oceans with 1st spaceborne synthetic-aperture radar (SAR). Demonstrated global monitoring of oceanic phenomena & determined requirements for ocean remote sensing. Tech Adv 68
Image result for polar wander wikimedia
1955: Gold showed mass redistribution on the surface or in the interior of Earth would result in a reorientation of the body w/respect to spin axis orientation. Subsequent studies of true polar wander advance understanding of Earth. Gold 1955, Sci Adv 67
2001: Measuring water loads with GNSS. van Dam et al. (2001) observed water loads in vertical component time series from nascent IGS network using models to quantify effects of groundwater, snowpack, & soil moisture. Tech Adv 66
1978: Seasat, 1st Earth-orbiting satellite for remote sensing of Earth's oceans with 1st spaceborne synthetic-aperture radar (SAR). Demonstrated global monitoring of oceanic phenomena & determined requirements for ocean remote sensing. Tech Adv 68
1970-1972: Used signal processing tools to extract an isostatic Green's Function (GF) from topographic and gravity data. Showed local isostasy, could be extracted from GFs. Dorman & Lewis 1970, Lewis & Dorman 1970, Dorman & Lewis 1972. Data Adv 65