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EMPIR project completes measurement campaigns to reduce uncertainty for geodesy measurements

Local tie survey at the Geodetic Observatory Wettzell, Germany, performed during the GeoMetre project with the TeleYAG-II interferometer developed in the project for this purpose (image: Paul Köchert/PTB)

Developing transfer standards disseminated to the SI metre and novel geodetic devices

The project

The ability to monitor environmental changes such as rising sea levels and tectonic movements relies on accurate geodetic measurements.

Modern geodesy measurements use the International Terrestrial Reference Frame (ITRF), maintained by the International Earth Rotation Service (IERS) using a global network of observation stations. Many of these stations utilise multiple instruments at the same site to make a range of geodetic measurements, which allows comparability between data.

However, establishing absolute uncertainties and metrological traceability chains for these measurements has been a challenge, and there is a strong need to reduce the uncertainty further. EMPIR project Large-scale dimensional measurements for geodesy (18SIB01, GeoMetre) developed measurements techniques and transfer standards for geodesy to reduce uncertainty and improve geodetic measurements based on Global Navigation Satellite Systems (GNSS) and Satellite Laser Ranging (SLR).

Reference point campaigns

All data tied to the ITRF relies on accurate measurement of the ‘local tie vectors’ connecting its reference points.

During the project, sixteen partners from different geodetic institutes and metrology institutes collaborated to reduce the uncertainty of these measurements, conducting multiple measurement campaigns at European geodetic co-location sites in Metsähovi, Finland, and Wettzell, Germany.

Several of these measurements have led to an immediate reduction in the uncertainty of the local tie vectors and have already been taken up for standards, contributing to the updated ITRF2020, while others are undergoing further development.

These results were jointly presented to the global geodetic community at the Reference Frames for Applications in Geosciences conference and at the Unified Analysis Workshop in 2022.

Project coordinator Florian Pollinger (PTB) has said of the project’s work:

“The GeoMetre project provided a unique opportunity to unite European experts in geodesy and metrology. Together, we could tackle the complex metrology challenge of the ‘local tie metrology’ from all angles, i.e., instrumentation, measurement strategy and analysis. Our results support geodesists in their important work to create a global reference frame which can be used, for example, to monitor critical global phenomena like the global sea level rise even better than today.”

This EMPIR project is co-funded by the European Union's Horizon 2020 research and innovation programme and the EMPIR Participating States.

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