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Ocean and mountains

Contributing to a better understanding of globally important environmental changes

The project

Geodetic reference frames form the backbone of all georeferencing services, providing the geospatial reference for global observations as sea level monitoring or Earth crustal movements.

To strengthen the complex traceability chain in this technical area, completed EMPIR project Large-scale dimensional measurements for geodesy (18SIB01, GeoMetre) focussed on two issues:

• the creation of new long-distances references for the Earth-bound verification of space-geodetic methods like Satellite Laser Ranging (SLR) or Global Navigation Satellite Systems (GNSS)

• the measurement of the local tie vectors, the geometric connection of reference points of co-located space-geodetic telescopes

The project developed specifically tailored instrumentation, including:

• new range meters capable of measuring up to 5 km in air with sub-millimetric uncertainty
• a metrologically-sound approach to GNSS-based distance measurement
• a 3D multilateration system for an outdoor working range of 50 m which reduces the measurement uncertainty compared to state-of-the-art systems by a factor of 3

Using these systems and methods, novel reference standards such as a new 5000 m reference network were established, and successful case studies for GNSS and SLR verification performed. For the first time, the local tie vector measurement was systematically tackled from multiple angles at two European space-geodetic co-location sites in a dedicated international project. The novel measurement systems, and also novel measurement and analysis approaches showed their potential to push the accuracy limits further, below the targeted uncertainty limit of 1 mm and can now be applied to other geographic sites.

EURAMET Technical Guide

The good practice guide written by the project consortium has recently been adopted by EURAMET as Technical Guide No. 6 Good practice guide on high-accuracy GNSS-based distance metrology.

This technical guide provides information on the use of Global Navigation Satellite System (GNSS) techniques for accurate distance determination with assessment of the corresponding uncertainty. Indications on field measurement practices, computation procedures, as well as available products to be used, are given. The estimation of uncertainties in the contributing error sources and their propagation to the distance determined contribute to the traceability and accuracy requirements needed in metrology.

Award

Joffray Guillory received the GKGM prize 2024 - an award issued by the Society for the Calibration of Geodetic Devices. With this award, the society recognised the many years of successful research work and the substantial scientific advances for the traceability of distance measurements. In particular, Dr. Guillory and his colleagues at CNAM built a prototype instrument that can be used outdoors, on different geodetic baselines under normal measurement conditions and to prove the high accuracy with a thorough quality assessment in accordance with the Guide to the expression of uncertainty in measurement. The systems recognised by this award were mainly developed and characterised in this project, building on the work of earlier projects LaVA and Surveying.

Project coordinator Florian Pollinger from PTB said

‘This project provided a fantastic opportunity for metrologists and geodesists from different backgrounds to work together. As a result, the project has been successful not only in developing novel instruments and refined procedures for long distance measurements, but also in verifying them in measurement campaigns at some of the most prestigious sites in Europe. The results of the project have significantly improved the SI traceability of long-range measurements for both terrestrial and GNSS-based techniques. The adoption of the good practice guide and the award to Joffray Guillory demonstrate the sustainability and growing community recognition of this work.’.
 

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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