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Logo: Sonderforschungsbereich geo-Q
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Logo: Sonderforschungsbereich geo-Q
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C04 - Regional gravity field modeling & relativistic geodesy

The chronometric leveling technique, a central application of relativistic geodesy within this SFB, provides directly gravity potential differences between two clocks (at rest on Earth). This technique is now becoming feasible for geodetic applications due to the development of optical clocks and links with targeted accuracies at the level of 10−18 (corresponds to 0.01 m in height); it has the great advantage of being independent of any other geodetic data and infrastructure, works in remote areas, and has the potential to replace the time-consuming and costly geometric leveling over longer distances, interconnect tide gauges on different islands, and control and unify different national height networks (i.e., solve the vertical datum problem in geodesy).

This project connects the areas of time metrology with optical clocks and classical physical geodesy. In the first instance, the classical and relativistic geodesy results will be used for a mutual validation, which is important to build confidence in the new generation optical clocks and the associated uncertainty budgets as well as in view of future geodetic applications of the optical clocks. For this purpose, geodetic knowledge on the gravity potential with best possible accuracy is first derived from the geometric leveling technique (together with gravity observations) and secondly from the results of gravity field modeling (e.g., disturbing potential, (quasi)geoid; based on the geodetic boundary value problem (GBVP) theory) and GNSS (Global Navigation Satellite System) positions (also denoted as GBVP/GNSS or geoid/GNSS approach); both approaches have their own particular strengths and limitations, with the geometric leveling technique giving superior accuracies over shorter distances (few km), while the GBVP/GNSS approach should be beneficial over longer distances (1000 km and more). In this context, the spatial gravity field modeling approach is generally preferred, which aims at the determination of the disturbing potential and the associated height anomalies or quasigeoid undulations at the Earth’s surface and its exterior, avoiding assumptions about the Earth’s interior gravity field (as needed in connection with the geoid).

Therefore, the major part of this project is related to the development of an improved high-resolution quasigeoid model for Central Europe, targeting in the long term (during the overall SFB funding period) at an accuracy of 1 cm or better. Initially, the mathematical modeling will be revised in parts regarding inherent approximations, the consideration of the atmosphere and topography, the linearization with respect to an existing high-degree reference geopotential model, as well as the combination, data weighting and error estimation procedure. Within a closed-loop simulation with synthetic data, this will lead to improved and comprehensively validated computer programs, which will then be employed for the practical computation of a best possible quasigeoid model based on the most up-to-date terrestrial gravity field data sets (gravity and terrain data) in combination with a corresponding global satellite gravity field model (possible candidates being the final GOCE models or corresponding models developed within other projects of this SFB). Based on this scenario, a standard deviation of about 2 cm (or slightly below) appears to be a realistic target for the quasigeoid heights, while further improvements require additional novel satellite data and missions as well as additional terrestrial data for selected areas.

The computed quasigeoid models will then be used together with GNSS and leveling observations at the relevant optical clock sites to support the chronometric leveling proof-of-principle experiments as central applications of relativistic geodesy within this SFB. The computed quasigeoid models will also be evaluated by independent GNSS/leveling stations and then employed for the interconnection of different height reference systems (vertical datums) in Europe as well as the definition and practical realization of a unified European height reference system, including the so-called geoid based vertical datum.

The main output of this project are i) the computed high-resolution quasigeoid (and associated geoid) models, ii) the results from the comparison of the new generation optical atomic clocks with classical geodesy observations, documenting the potential of the optical clocks for geodetic applications, as well as iii) the estimated offsets between different national height systems in Europe and iv) a concept for the possible implementation of a unified European and global height reference system.

Scientists working on this project

Lin Miao
email: linmiaoife.uni-hannover.de

phone: +49 511 762-5176
details

Dr.-Ing. Ludger Timmen
email: timmenife.uni-hannover.de

phone: +49 511 762 3398
details

Selected Publications


Peer-Reviewed Literature

Voigt C., Denker H. and Timmen L.  (2016): Time-variable gravity potential components for optical clock comparisons and the definition of international time scales, Metrologia, Volume 53, Number 6 more
DOI: 10.1088/0026-1394/53/6/1365


Non Peer-Reviewed Literature

Denker H. (2015): A new European gravimetric (quasi)geoid EGG2015, XXVI General Assembly of the International Union of Geodesy and Geophysics (IUGG), Earth and Environmental Sciences for Future Generations, Prague, Czech Republic, 22 June – 02 July 2015, Abstract G02p-424

Denker H., Timmen L. and Voigt C. (2015): Gravity field modelling for optical clock comparisons, XXVI General Assembly of the International Union of Geodesy and Geophysics (IUGG), Earth and Environmental Sciences for Future Generations, Prague, Czech Republic, 22 June – 02 July 2015, Abstract G02p-431

Voigt C., Denker H. and Timmen L. (2015): Investigation of time-variable components of the gravity potential for optical clock comparisons, XXVI General Assembly of the International Union of Geodesy and Geophysics (IUGG), Earth and Environmental Sciences for Future Generations, Prague, Czech Republic, 22 June – 02 July 2015, Abstract G02p-423
DOI: 10.1088/0026-1394/53/6/1365


Presentations, Talks and Posters

Grosche G., Lisdat C., Quintin N., Shi C., Raupach S. M. F., Grebing C., Nicolodi D., Stefani F., Al-Masoudi A., Dörscher S., Häfner S., Robyr J.-L., Chiodo N., Bilicki S., Bookjans E., Koczwara A., Koke S., Kuhl A., Wiotte F., Meynadier F., Camisard E., Abgrall M., Lours M., Legero T., Schnatz H. Sterr U. Denker H., Charonnet C., Le Coq Y. Santarelli G., Amy-Klein A., Le Targat R., Lodewyck J., Lopez O. and Pottie P.-E. (2017): 1400 km optical fiber link tests whether French and German clocks tick alike, Precise Time and Time Interval Meeting, Monterey, California, USA, 30 January – 2 February, 2017

Grotti J., Koller S., Vogt S., Al-Masoudi A., Dörscher S., Herbers S., Häfner S., Sterr U., Lisdat C., Denker H., Pizzocaro M., Thoumany P., Rauf B., Clivati C., Levi F., Calonico D., Rlland A., Baynes F. and Margolis H. (2017): First campaigns with PTB transportable optical lattice clock, Verhandlungen der Deutschen Physikalischen Gesellschaft e.V., Q13.4, Vortrag, Mainz, 06 March, 2017 more

Denker H. (2016): A new European Gravimetric (Quasi)Geoid EGG2015, First Joint Comm. 2 and IGFS Meeting, Internat. Symp. on Gravity, Geoid and Height Systems 2016, GGHS2016, Thessaloniki, Greece, 19 – 23 September, 2016

Denker H. (2016): A new European gravimetric (quasi)geoid EGG2015, 1st Joint Commission 2 and IGFS Meeting, International Symposium on Gravity, Geoid and Height Systems 2016, GGHS2016, Thessaloniki, Greece, Sept. 19-23, 2016

Denker H., Timmen L. and Voigt C. (2016): Gravity potential for optical clock comparisons, Optical clocks: quantum engineering and international timekeeping, Workshop, Joint EMRP project consortia: ITOC & QESOCAS, University of York, UK, 08 April, 2016

Denker H., Timmen L. and Voigt C. (2016): Gravity field modelling with regard to optical clock comparisons, First Joint Comm. 2 and IGFS Meeting, Internat. Symp. on Gravity, Geoid and Height Systems 2016, GGHS2016, Thessaloniki, Greece, 19 – 23 September, 2016

Denker H., Timmen L. and Voigt C. (2016): Geodetic contributions to the project “International Timescales with Optical Clocks (ITOC)", First Joint Comm. 2 and IGFS Meeting, Internat. Symp. on Gravity, Geoid and Height Systems 2016, GGHS2016, Thessaloniki, Greece, 19 – 23 September, 2016

Denker H., Timmen L. and Voigt C. (2016): Gravity field modelling with regard to optical clock comparisons, 1st Joint Commission 2 and IGFS Meeting, International Symposium on Gravity, Geoid and Height Systems 2016, GGHS2016, Thessaloniki, Greece, Sept. 19-23, 2016

Lin M. and Denker H. (2016): Comparison of various methods for modeling gravitational effects of the topography, First Joint Comm. 2 and IGFS Meeting, Internat. Symp. on Gravity, Geoid and Height Systems 2016, GGHS2016, Thessaloniki, Greece, 19 – 23 September, 2016

Margolis H. S., Benkler E., Calonico D., Denker H., Delva P., Godun R. M., Lisdat C., Abgrall M., Achkar J., Al-Masoudi A., Barwood G. P., Baynes F. N., Baynham C. F. A., Bilicki S., Bize S., Bookjans E., Bowden W., Cerretto G., Chupin B., Clivati C., Donnellan S., Dörscher S., Fordell T., Gerginov V., Gersl J., Gill P., Grebing C., Guéna, J., Häfner S., Hill I. R., Hobson R., Huang G., Huntemann N., Jones J.M., Kind S. A., Klein H. A., Lamb A., Le Coq Y., Le Targat R., Leute J., Lindvall T., Lipphardt B., Lodewyck J., Menchetti M., Merimaa M., Mura A., Nicoldi D., Nisbet-Jones P. B. R., Ozimek F., Peik E., Pizzocaro M., Piester D., Riedel F., Robyr J.-L., Rolland A., Rosenbusch P., Rovera D., Rust F., Sanner C., Sesie I., Shemar S. L., Shi C., Sterr U., Szymaniec K., Tamm C., Timmen L., Vogt S., Voigt, C. Wallin A. E., Weyes S. and Whibberley P.B. (2016): Towards international timescales with optical clocks, First Joint Comm. 2 and IGFS Meeting, Internat. Symp. on Gravity, Geoid and Height Systems 2016, GGHS2016, Thessaloniki, Greece, 19 – 23 September, 2016

Voigt C., Denker H. and Timmen L. (2016): Time-variable components of the gravity potential field, Optical clocks: quantum engineering and international timekeeping, Workshop, Joint EMRP project consortia: ITOC & QESOCAS, University of York, UK, 08 April, 2016

Denker H. (2015): Gravity potential for optical clocks, Lecture, OCS2015, 1st School on Optical Clocks, Torino, Italy, 29 June – 03 July, 2015

Lin M., Denker H. and Müller J. (2015): Regional gravity field modeling using a two-step point mass method applied to the IAG JSG0.3 test data, Abstract G02p-412, XXVI General Assembly of the International Union of Geodesy and Geophysics (IUGG), Earth and Environmental Sciences for Future Generations, Prague, Czech Republic, 22 June – 02 July, 2015

Margolis H. S., Benkler E., Calonico D., Denker H., Delva P., Godun R. M., Lisdat C., Achkar J., Bize S., Gersl J., Gill P., Lindvall T., Merimaa M., Pizzocaro M., Piester D., Riedel F., Sesia I., Shemar S. L., Sterr U., Timmen L., Voigt C., Vogt S., Weyers S. and Whibberley, P. B. (2015): ITOC: international timescales with optical clocks, Abstract Book, 2015 Joint Conference of the IEEE International Frequency Control Symposium & European Frequency and Time Forum, Denver, Colorado, USA, 12 - 16 April, 2015

Margolis H. S., Benkler E., Calonico D., Denker H., Delva P., Godun R. M., Lisdat C., Gersl J. and Merimaa M. (2015): ITOC: international timescales with optical clocks, Abstract G01p-247, XXVI General Assembly of the International Union of Geodesy and Geophysics (IUGG), Earth and Enviromental Sciences for Future Generations, Prague, Czech Republic, 22 June - 02 July, 2015 more

Margolis H. S., Benkler E., Calonico D., Denker H., Delve P., Godun R. M., Lisdat C., Gersl J, Merimaa M. and members of the ITOC consortium (2015): Towards international timescales with optical clocks, Program and Book of Abstracts, 8th Symposium on Frequency Standards and Metrology 2015, Potsdam, Germany, 12 – 26 October, 2015

Voigt C., Denker H. and Timmen L. (2015): Investigation of time-variable components of the gravity potential for optical clock comparisons, Abstract G02p-423, XXVI General Assembly of the International Union of Geodesy and Geophysics (IUGG), Earth and Environmental Sciences for Future Generations, Prague, Czech Republic, 22 June – 02 July, 2015