Indoor height determination of the new absolute gravimetric station of L'Aquila

In this paper we describe all the field operations and the robust post-processing proceduresto determine the height of the new absolute gravimetric station purposely selected to belong to a new absolute gravimetric network and located in the Science Faculty of the L’Aquila University. This site has been realized indoor in the Geomagnetism laboratory, so that the height cannot be measured directly, but linking it to the GNSS antenna of AQUI benchmark located on the roof of the same building, by a classical topographic survey. After the topographic survey, the estimated height difference between AQUI and the absolute gravimetric site AQUIgis 14.9700.003 m. At the epoch of the 2018 gravimetric measures, the height of AQUI GNSS station was 712.9740.003 m, therefore the estimated ellipsoidalheight of the gravimetric site at the epoch of gravity measurements is 698.0040.005 m. Absolute gravity measurements are referred to the equipotential surface of gravity field, so that the knowledge of the geoidal undulation at AQUIg allows us to infer the orthometric height as 649.32 m.

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Optical clocks for gravity field observation and further geodetic applications

10.5194/egusphere-egu2020-10476 ◽

2020 ◽

Author(s):

Hu Wu ◽

Jürgen Müller ◽

Annike Knabe

Keyword(s):

Gravity Field ◽

Rapid Development ◽

Satellite Orbit ◽

Equipotential Surface ◽

Gravity Potential ◽

Height Difference ◽

The Earth ◽

Temporal Gravity ◽

Reference Clock

In the past three decades, optical clocks and frequency transfer techniques have experienced a rapid development. They are approaching a fractional frequency uncertainty of 1.0x10-18, corresponding to about 1.0 cm in height. This makes them promising to realize &#8220;relativistic geodesy&#8221;, and it opens a new door to directly obtain gravity potential values by the comparison of clock frequencies. Clocks are thus considered as a novel candidate for determining the Earth&#8217;s gravity field. We propose to use a spaceborne clock to obtain gravity potential values along a satellite orbit through its comparison with reference clocks on ground or with a co-orbital clock. The sensitivity of clock measurements is mapped to gravity field coefficients through closed-loop simulations.In addition, clocks are investigated for other geodetic applications. Since they are powerful in providing the height difference between distant sites, clocks can be applied for the unification of local/regional height systems, by estimating the offsets between different height datums and the systematic errors within levelling networks. In some regions like Greenland, clocks might be a complementary tool to GRACE(-FO) for detecting temporal gravity signals. They can be operated at locations of interest and continuously track changes w.r.t. reference clock stations. The resulting time-series of gravity potential values reveal the temporal gravity signals at these points. Moreover, as the equipotential surface at a high satellite altitude is more regular than that on the Earth&#8217;s surface, a couple of clocks in geostationary orbits can realize a space-based reference for the determination of physical heights at any point on the Earth through clock comparisons.We gratefully acknowledge the financial support by the Deutsche Forschungsgemeinschaft (DFG) under Germany&#8217;s Excellence Strategy EXC-2123/1 (Project-ID: 390837967).

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Strategy for the realisation of the International Height Reference System (IHRS)

Journal of Geodesy ◽

10.1007/s00190-021-01481-0 ◽

2021 ◽

Vol 95 (3) ◽

Cited By ~ 4

Author(s):

Laura Sánchez ◽

Jonas Ågren ◽

Jianliang Huang ◽

Yan Ming Wang ◽

Jaakko Mäkinen ◽

...

Keyword(s):

Gravity Field ◽

Reference System ◽

International Association ◽

Accuracy Assessment ◽

Equipotential Surface ◽

Precise Determination ◽

Gravity Models ◽

Reference Network ◽

Global Gravity Models

AbstractIn 2015, the International Association of Geodesy defined the International Height Reference System (IHRS) as the conventional gravity field-related global height system. The IHRS is a geopotential reference system co-rotating with the Earth. Coordinates of points or objects close to or on the Earth’s surface are given by geopotential numbersC(P) referring to an equipotential surface defined by the conventional valueW0 = 62,636,853.4 m2 s−2, and geocentric Cartesian coordinatesXreferring to the International Terrestrial Reference System (ITRS). Current efforts concentrate on an accurate, consistent, and well-defined realisation of the IHRS to provide an international standard for the precise determination of physical coordinates worldwide. Accordingly, this study focuses on the strategy for the realisation of the IHRS; i.e. the establishment of the International Height Reference Frame (IHRF). Four main aspects are considered: (1) methods for the determination of IHRF physical coordinates; (2) standards and conventions needed to ensure consistency between the definition and the realisation of the reference system; (3) criteria for the IHRF reference network design and station selection; and (4) operational infrastructure to guarantee a reliable and long-term sustainability of the IHRF. A highlight of this work is the evaluation of different approaches for the determination and accuracy assessment of IHRF coordinates based on the existing resources, namely (1) global gravity models of high resolution, (2) precise regional gravity field modelling, and (3) vertical datum unification of the local height systems into the IHRF. After a detailed discussion of the advantages, current limitations, and possibilities of improvement in the coordinate determination using these options, we define a strategy for the establishment of the IHRF including data requirements, a set of minimum standards/conventions for the determination of potential coordinates, a first IHRF reference network configuration, and a proposal to create a component of the International Gravity Field Service (IGFS) dedicated to the maintenance and servicing of the IHRS/IHRF.

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The Role and Capability of Absolute Gravity Measurements in Determining the Temporal Variations in the Earth’s Gravity Field

International Association of Geodesy Symposia - Global Gravity Field and Its Temporal Variations ◽

10.1007/978-3-642-61140-7_3 ◽

1996 ◽

pp. 20-29 ◽

Cited By ~ 6

Author(s):

A. Lambert ◽

T. S. James ◽

J. O. Liard ◽

N. Courtier

Keyword(s):

Gravity Field ◽

Temporal Variations ◽

Absolute Gravity ◽

Earth’S Gravity Field ◽

Gravity Measurements

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Gravity reference at the Argentinean–German Geodetic Observatory (AGGO) by co-location of superconducting and absolute gravity measurements

Journal of Geodesy ◽

10.1007/s00190-020-01402-7 ◽

2020 ◽

Vol 94 (9) ◽

Author(s):

Ezequiel D. Antokoletz ◽

Hartmut Wziontek ◽

Claudia N. Tocho ◽

Reinhard Falk

Keyword(s):

Gravity Data ◽

Total Error ◽

International Comparisons ◽

Superconducting Gravimeter ◽

Calibration Factor ◽

Absolute Gravity ◽

Absolute Level ◽

Gravity Measurements ◽

Instrumental Drift

AbstractThe Argentinean–German Geodetic Observatory (AGGO) is a fundamental geodetic observatory located close to the city of La Plata, Argentina. Two high-precision gravity meters are installed at AGGO: the superconducting gravimeter SG038, which is in operation since December 2015, and the absolute gravimeter FG5-227, which has provided absolute gravity measurements since January 2018. By co-location of gravity observations from both meters between January 2018 and March 2019, calibration factor and instrumental drift of the SG038 were determined. The calibration factor of the SG038 was estimated by different strategies: from tidal models, dedicated absolute gravity measurements over several days and a joint approach (including the determination of the instrumental drift) using all available absolute gravity data. The final calibration factor differs from the determination at the previous station, the transportable integrated geodetic observatory, in Concepcion, Chile, by only 0.7‰, which does not imply a significant change. From the combined approach also the mean absolute level of the SG was determined, allowing to predict absolute gravity values from the SG at any time based on a repeatability of $$12\,\hbox {nm}/\hbox {s}^{2}$$ 12 nm / s 2 for the FG5-227 at AGGO. Such a continuous gravity reference function provides the basis for a comparison site for absolute gravimeters in the frame of the international gravity reference frame for South America and the Caribbean. However, it requires the assessment of the total error budget of the FG5-227, including the link to the international comparisons, which will be subject of future efforts.

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Indoor height determination of the new absolute gravimetric station of L'Aquila

10.5194/egusphere-egu2020-8834 ◽

2020 ◽

Author(s):

Augusto Mazzoni ◽

Marco Fortunato ◽

Alberico Sonnessa ◽

Giovanna Berrino ◽

Filippo Greco ◽

...

Keyword(s):

Reference Point ◽

Absolute Gravity ◽

Height Difference ◽

Satellite Systems ◽

Height Determination ◽

Ground Deformations ◽

Space Agency ◽

Italian Space Agency ◽

Physics Department ◽

Postseismic Relaxation

In 2018 INGV funded a project aimed to detect gravity variations and ground deformations over different time-scale possibly associated with the postseismic relaxation affecting the area where the recent seismic events of L'Aquila (2009 Mw 6.3) and Amatrice-Norcia (2016 Mw 6.1 and 6.5) took place. To this aim a network of five absolute gravity stations was realized (Terni, Popoli, Sant&#8217;Angelo Romano, L&#8217;Aquila University and L'Aquila Laboratori Nazionali del Gran Sasso). The site of L'Aquila University was chosen since location of the permanent GNSS station (AQUI) managed by the Italian Space Agency and contributing to the EUREF network. AQUI is continuously operating on the roof of the Science Faculty (Coppito, L'Aquila).In the basement of the same building we realized the absolute gravimetric station (AQUIg), indoor the Geomagnetic laboratory of the Physics Department. This is one of the numerous applications where satellite systems must be integrated with traditional terrestrial surveying techniques. These include the case of underground or indoor gravimetric surveys, where the height of the gravimetric reference point should be determined precisely starting from an outdoor reference point with known coordinates. In this case, the use of classical observation techniques and instruments (e.g., total stations, levels) is crucial to measure the height difference between a reference GNSS station and a gravimetric benchmark. We will draw the steps followed to estimate the height difference between AQUIg and AQUI by a classical topographic survey and therefore the height of AQUIg from estimating first the height of AQUI.

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Gravity field modelling and gravimetry

Geodesy and Cartography ◽

10.1515/geocart-2015-0012 ◽

2015 ◽

Vol 64 (2) ◽

pp. 177-200 ◽

Cited By ~ 2

Author(s):

Jan Krynski

Keyword(s):

Gravity Field ◽

Temporal Variations ◽

Absolute Gravity ◽

Satellite Gravity ◽

Gravity Field Modelling ◽

Field Modelling ◽

Use Of Data ◽

Research Activities ◽

Geopotential Models

Abstract The summary of research activities concerning gravity field modelling and gravimetric works performed in Poland in the period of 2011-2014 is presented. It contains the results of research on geoid modelling in Poland and other countries, evaluation of global geopotential models, determination of temporal variations of the gravity field with the use of data from satellite gravity space missions, absolute gravity surveys for the maintenance and modernization of the gravity control in Poland and overseas, metrological aspects in gravimetry, maintenance of gravimetric calibration baselines, and investigations of the nontidal gravity changes. The bibliography of the related works is given in references.

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Gravity data collection with a CG5 gravitymeter for densification of the gravity data around the AUT1 IHRF station

10.5194/egusphere-egu21-1677 ◽

2021 ◽

Author(s):

Dimitrios A. Natsiopoulos ◽

Elisavet G. Mamagiannou ◽

Eleftherios A. Pitenis ◽

Georgios S. Vergos ◽

Ilias N. Tziavos ◽

...

Keyword(s):

Gravity Data ◽

Gravity Anomalies ◽

Absolute Gravity ◽

Dual Frequency ◽

Height Determination ◽

Free Air ◽

Gravity Measurements ◽

Gravity Database ◽

Free Air Gravity ◽

Geological Complexity

Within the GeoGravGOCE project, funded by the Hellenic Foundation for Research Innovation, a main goal has been the densification of the available land gravity database around the eastern part of the city of Thessaloniki, Greece, where the core International Height Reference Frame (IHRF) station AUT1 is located in order to improve regional geoid and potential determination. Hence it was deemed necessary to densify the available gravity data within radiuses of 10 km, 20 km, 50 km and 100 km from the AUT1 core IHRF site. In that frame, and given the geological complexity of the region surrounding Thessaloniki and the significant variations of the terrain, gravity campaigns were appropriately designed and gravity measurements were carried out in order to densify the database and cover as much as possible traverses of varying altitude. The measurements have been carried out with the CG5 gravity meter of the GravLab group and dual-frequency GNSS receivers in RTK mode for orthometric height determination. In this &#160;study we provide details of the gravity campaigns, the measurement principle and the finally derived gravity and free-air gravity anomalies. The mean measurement accuracy achieved was at the ~20 &#956;Gal level for the gravity measurements and ~3 cm for the orthometric heights. In all cases the final derived gravity value was based on the absolute point established by the GravLab team at the AUTH seismological station premises with the A10 (#027) absolute gravity meter.

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Towards a Global Unified Physical Height System

10.5194/egusphere-egu21-1500 ◽

2021 ◽

Author(s):

Laura Sanchez ◽

Jianliang Huang ◽

Riccardo Barzaghi ◽

Georgios S. Vergos

Keyword(s):

Gravity Field ◽

Reference Frame ◽

Reference System ◽

International Association ◽

Equipotential Surface ◽

Terrestrial Reference Frame ◽

Global Network ◽

Main Challenge ◽

Physical Height

The International Association of Geodesy (IAG), as the organisation responsible for advancing Geodesy, introduced in 2015 the International Height Reference System (IHRS) as the global conventional reference system for the determination of gravity field-related vertical coordinates. The definition of the IHRS is given in terms of potential parameters: the vertical coordinates are geopotential numbers (CP = W0 &#8208; WP) referring to an equipotential surface of the Earth's gravity field realised by the conventional value W0 = 62 636 853.4 m2s&#8208;2. The spatial reference of the position P for the potential WP = W(X) is given by coordinates X of the International Terrestrial Reference Frame (ITRF). At present, the main challenge is the realisation of the IHRS; i.e., the establishment of the International Height Reference Frame (IHRF): a global network with regional and national densifications, whose geopotential numbers referring to the global IHRS are known. According to the objectives of the IAG Global Geodetic Observing System (GGOS), the target accuracy of these global geopotential numbers is 3 x 10-2 m2s-2. In practice, the precise realisation of the IHRS is limited by different aspects; for instance, there are no unified standards for the determination of the potential values WP; the gravity field modelling and the estimation of the position vectors X follow different conventions; the geodetic infrastructure is not homogeneously distributed globally, etc. This may restrict the expected accuracy of 3 x 10-2 m2s-2 to some orders lower (from 10 x 10-2 m2s-2 to 100 x 10-2 m2s-2). This contribution summarises advances and present challenges in the establishment of the IHRS/IHRF.

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Forty-three years of absolute gravity observations of the Fennoscandian postglacial rebound in Finland

Journal of Geodesy ◽

10.1007/s00190-020-01470-9 ◽

2021 ◽

Vol 95 (2) ◽

Author(s):

Mirjam Bilker-Koivula ◽

Jaakko Mäkinen ◽

Hannu Ruotsalainen ◽

Jyri Näränen ◽

Timo Saari

Keyword(s):

Gravity Data ◽

Gravity Change ◽

Global Navigation Satellite Systems ◽

Absolute Gravity ◽

Data Sets ◽

Postglacial Rebound ◽

Land Uplift ◽

Satellite Systems ◽

Gravity Measurements ◽

Global Navigation Satellite

AbstractPostglacial rebound in Fennoscandia causes striking trends in gravity measurements of the area. We present time series of absolute gravity data collected between 1976 and 2019 on 12 stations in Finland with different types of instruments. First, we determine the trends at each station and analyse the effect of the instrument types. We estimate, for example, an offset of 6.8 μgal for the JILAg-5 instrument with respect to the FG5-type instruments. Applying the offsets in the trend analysis strengthens the trends being in good agreement with the NKG2016LU_gdot model of gravity change. Trends of seven stations were found robust and were used to analyse the stabilization of the trends in time and to determine the relationship between gravity change rates and land uplift rates as measured with global navigation satellite systems (GNSS) as well as from the NKG2016LU_abs land uplift model. Trends calculated from combined and offset-corrected measurements of JILAg-5- and FG5-type instruments stabilized in 15 to 20 years and at some stations even faster. The trends of FG5-type instrument data alone stabilized generally within 10 years. The ratio between gravity change rates and vertical rates from different data sets yields values between − 0.206 ± 0.017 and − 0.227 ± 0.024 µGal/mm and axis intercept values between 0.248 ± 0.089 and 0.335 ± 0.136 µGal/yr. These values are larger than previous estimates for Fennoscandia.

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