JPL Scientists Help Update Worldwide Terrestrial Reference Framework

Scientists from NASA’s Jet Propulsion Laboratory in Pasadena were part of a team that recently contributed to an update to a global navigation standard called the International Terrestrial Reference Frame or ITRF, which is the invisible foundation for modern global positioning and navigation.

All kinds of satellite and spacecraft navigation, studies of our changing planet, and your mobile-phone apps for driving directions rely on this foundation. It is also the framework that pilots and navigators on board commercial or military aircraft and their controllers on the ground depend on to determine aircraft positions.

More importantly, the ITRF serves as the foundation for very precise measurements of changes on the surface of the Earth and in its oceans so that scientists can trace the effects of earthquakes, volcanic eruptions, landslides, floods and changes in sea level and ice sheets over time and help mitigate their impact.

“The new release lays the groundwork for more detailed studies than ever before of global changes in Earth’s ocean, ice sheets, land and atmosphere,” said Stephen Merkowitz, manager of NASA’s Space Geodesy Project at the Goddard Space Flight Center in Greenbelt, Maryland.

The update was issued by the International Earth Rotation and Reference Systems Service’s International Terrestrial Reference System Product Center at the Institut National de l’Information Géographique et Forestière, known as IGN, in Paris.

Officially called ITRF2014, the ITRF update was released in late January and is the ninth ITRF issued since 1992. More than 1,000 observing stations run by NASA and other scientific institutions worldwide contributed to it, collecting data through 2014.

NASA’s Space Geodesy Project, which helps to improve the ITRF, uses four measurement techniques to collect data for the reference frame. These are Satellite Laser Ranging, Very Long Baseline Interferometry (VLBI), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and use of the Global Navigation Satellite System (GNSS).

“The big advantage of GNSS is the dense network of stations distributed around the world,” said Richard Gross, who manages the Terrestrial Reference Frame combination center at JPL. “For the reference frame, on the order of a thousand GNSS stations contribute position measurements.”

Research teams worldwide analyzed 20 to 30 years of data for each method in preparation for the new ITRF updates. Scientists at JPL’s Terrestrial Reference Frame combination center contributed much of the GNSS data.