SC 2.1: Land, Marine and Airborne Gravimetry
Chair: Derek van Westrum (USA)
Vice-Chair: Przemyslaw Dykowski (Poland)
Terms of Reference
Geodesists and geophysicists utilize gravity and gravity gradient datasets from a wide variety of sources: local relative gravity campaigns, pointwise absolute gravity observations, gravity variation in time at fixed locations, and continental scale observations from marine and airborne platforms. These observations need to be consistent with each other, consistent with satellite-based results, and have well defined accuracy/uncertainty determinations. IAG Sub-commission 2.1, "Land, Marine and Airborne Gravimetry: Standards, Observations, and Innovation,” aims to bring together scientists from all over the globe that are interested in the instruments, techniques, and analysis of terrestrial, marine and airborne gravity and gravity gradient measurements.
Objectives
SC2.1 provides the scientific community with the means to assess the accuracy of absolute gravity observations through the organization of regular international absolute gravimeter comparisons. These efforts are in cooperation with the metrology community: the Consultative Committee on Mass and Related Quantities, its Working Group on Gravimetry (CCM WGG), and other Regional Metrology Organizations as well as all interested scientific institutions. The relationship allows for direct traceability of gravity data to international standards.
SC2.1 supports the dissemination of the results of these activities through an international absolute gravity database, which in turn, will support the ongoing realization of a new and improved International Gravity Reference Frame.
SC2.1 supports sharing expertise and experience in performing gravity surveys on moving platforms (Marine, Airborne) allowing for the collection of the highest possible quality gravity data using the most up to date techniques.
To facilitate the exchange of all terrestrial gravity data and metadata, SC2.1 is actively supporting the creation of a unified file format in an open source environment.
Finally, SC2.1 promotes research and development into new instruments and techniques by stimulating communication and cooperation between scientific groups. The sub-commission will encourage regional meetings and workshops dedicated to specific problems when and where appropriate.
Program of Activities
- Host the JWG2.1.1, “Establishment of an International Gravity Reference Frame”, along with IGFS, BGI and IGETS
- Provide access to the results of comparisons of absolute gravimeters via the AGrav database at BKG-BGI
- Host the JWG 2.1.2 “Unified file formats and processing software for high-precision gravimetry,” along with IGFS, BGI and IGETS
- Host the SG2.1.1 “Developments in near Earth gravimetry: instruments, analysis, and applications”
- Appoint the Steering Committee consisted of the members experienced in the fields of gravimetry related to the activities of SC2.1 and the contact persons for European, East Asia and Western Pacific, South America and North America Gravity Networks.
- Support IAG Commission 2 Symposia such as GGHS.
Working Groups of Sub-Commission 1.1
JWG 2.1.1: Establishment of the International Gravity Reference Frame
(joint with IGFS, BGI, IGETS)
Chair: Hartmut Wziontek (Germany)
Vice-Chair: Sylvain Bonvalot (France)
Terms of Reference
One task of IAG's Commission 2 “Gravity Field” is the establishment of the International Gravity Reference System and Frame (IGRF). These activities are motived by the IAG Resolutions No. 2 of 2015 (IUGG General Assembly Prague) and No. 4 of 2019 (IUGG General Assembly Montreal). The IAG Sub-Commission 2.1 “Land, Marine and Airborne Gravimetry” promotes consistency and compatibility of gravity and gravity gradient datasets and assessment of their accuracy. The International Gravity Field Service IGFS coordinates the servicing of the geodetic and geophysical community with gravity field related data, software and information. A modern and precise absolute gravity reference frame will not only contribute to the establishment of the Global Geodetic Reference Frame (GGRF) of the UN, but will also serve as a long-term and precise gravity reference for the IAG Global Geodetic Observing System (GGOS).
Objectives
Within IAG Sub-Commission 2.1 “Land, Marine and Airborne Gravimetry” the realization of the International Gravity Reference Frame (IGRF) will be initiated. The IGRF is the realization of the International Gravity Reference System (IGRS). The IGRS is defined by the observation of the instantaneous acceleration of free fall, the traceability of these observations to the International System of Units (SI), and a set of conventional corrections for the time independent components of gravity effects. The IGRF as the realization of the IGRS is based on observations with absolute gravimeters (AG) which are monitored at reference stations and during comparisons. The IGRF further defines a set of conventional models for the correction of temporal gravity changes. Finally, the IGRF demands a compatible infrastructure accessible to end-users.
The JWG focuses on the establishment of such infrastructure in cooperation with IGFS, GGOS, international and national institutions, agencies, and governmental bodies. This infrastructure should consist of reference stations on the national level for the monitoring of AGs. On the international level, comparison stations will provide the facilities to check the compatibility of AGs, and core stations will link to space geodetic techniques and the International Height Reference Frame (IHRF).
The absolute gravity database “AGrav” which already is a fixed part of the BGI (International Gravimetric Bureau) services is proposed to serve as a central inventory to document all IGRF stations and related AG observations.
A close cooperation with the International Geodynamics and Earth Tide Service (IGETS) supports the continuous monitoring at the gravity reference stations.
The activities should be further aligned with the JWG on the Implementation of the International Height Reference Frame.
Members
Mirjam Bilker Koivula (Finland)
Przemyslaw Dykowski (Poland)
Andreas Engfeldt (Sweden)
Reinhard Falk (Germany)
Jaakko Mäkinen (Finland)
Urs Marti (Switzerland)
Jack McCubbine (Australia)
Ilya Oshchepkov (Russia)
Vojtech Palinkas (Czech Republic)
Victoria Smith (UK)
Ludger Timmen (Germany)
Claudia Tocho (Argentina)
Christian Ullrich (Austria)
Michel van Camp (Belgium)
Derek van Westrum (USA)
Marc Véronneau (Canada)
Leonid Vitushkin (Russia)
Shuqing Wu (China)Toshihiro Yahagi (Japan)
Corresponding Members
Jonas Ågren (Sweden)
Mauro Andrade de Sousa (Brazil)
Daniel Barnes (USA)
Henri Baumann (Switzerland)
Denizar Blitzkow (Brazil)
Jean-Paul Boy (France)
Ana Cristina O. Cancoro de Matos (Brazil)
In-Mook Choi (Korea)
Alfredo Esparza (Mexico)Olivier Francis (Luxemburg)
Yoichi Fukuda (Japan)
Alessandro Germak (Italy)
Joe Henton (Canada)
Jacques Hinderer (France)
Domenico Iacovone (Italy)
Shuanggen Jin (China)
Janis Kaminskis (Latvia)
Jeff Kennedy (USA)
Jakub Kostelecky (Czech Republic)
Jan Krynski (Poland)
Jacques Liard (Canada)
Jose Manuel Serna Puente (Spain)
Camilo Matiz (Colombia)
Koji Matsuo (Japan)
Leidy Johanna Moisés Sepúlveda (Colombia)
Per-Anders Olsson (Sweden)
Tomasz Olszak (Poland)
Diego Piñón (Argentina)
Andrea Prato (Italy)
Rene Reudink (Netherlands)
Axel Rülke (Germany)
Laura Sanchez (Germany)
Roman Sermyagin (Russia)
Heping Sun (China)
V.M. Tiwari (India)
JWG 2.1.2: Unified file formats and processing software for high-precision gravimetry Frame
(joint with IGFS, IGETS, BGI)
Chair: Ilya Oshchepkov (Russia)
Vice-Chair: Vojtech Pálinkáš (Czech Republic)
Terms of Reference
Absolute gravity measurements have become widely used in geodesy since the 1970s when several transportable absolute gravimeters were introduced, since then their number has increased dramatically and continues to do so. The absolute gravimeters are used not only in geodesy, but also in metrology, geophysics, hydrology and other applications. The IAG's Commission 2 “Gravity Field” and its JWG 2.1.1 are working on the establishment of the International Gravity Reference System/Frame (IGRS/IGRF), which will be based solely on the absolute gravity measurements. The latter task will require a possibility for re-processing of all historical, current and future data, as well as their long-term availability for all interested parties.
The current ability to exchange and to re-process raw data of absolute gravity measurements is limited by the fact that each manufacturer uses their own proprietary software and different data storage formats. Also differences in the implementation of processing standards may exist. In such a situation it is difficult to ensure reproducibility and traceability to the SI of an individual experiment. Another difficulty arises from the requirement for a re-processing of old measurements after the introduction of new processing standards, when neither data nor software are available anymore.
The JWG 2.1.2 aims to create a unified, meter and software independent, format for storing and sharing not only the processing results and metadata, but also the raw data of gravity measurements. Different software will be evaluated and discrepancies will be discovered and resolved. Perspectively, an open source software should be established to eliminate the above mentioned problems, as well as to implement a standard procedure for handling absolute gravity measurements for the IGRF. The activities need a close cooperation with the manufacturers of absolute gravimeters in order to align instrument specific data handling and a transparent processing and to implement a common exchange format.
Objectives
- Review of existing software, data types, data formats and processing standards in high-precision gravimetry; develop requirements for a unified format and data processing software.
- Test of the compatibility of existing software
- Develop a unified data storage format for a high-precision gravity measurements: description, converter and software implementation.
- Develop a unified processing software to process any high-precision gravity measurements with a wide support for any processing procedure.
Members
Brian Ellis (USA)
Julian Glässel (Germany)
Jacques Liard (Canada)
Jeff Kennedy (USA)
Jaakko Mäkinen (Finland)
Vojtech Pálinkáš (Czech Republic)
Sergey Svitlov (Germany)
Pierre Vermeulen (France)
Marc Véronneau (Canada)
Hartmut Wziontek (Germany)
SG 2.1.1: Developments in Gravity Instrumentation, Analysis, and Applications
Chair: Derek van Westrum (USA)
Vice-Chair: Przemyslaw Dykowski (Poland)
Terms of Reference
SG2.1.1 is focused on methods and instrumentation used in collecting and analyzing terrestrial (non-satellite) gravity and gravity gradiometry data. New developments in both “classic” and quantum absolute instruments, as well as novel relative instruments, are happening a rapid pace and are of great interest to the geodetic community. In addition, communication of such developments between the geodesy community and metrology community is essential.
SG2.1.1 also supports research in the analysis of gravity data. Examples include standard absolute corrections, barometric loading, reduction of relative gravity networks, software, and file formats.
SG2.1.1 also promotes innovations in the use of gravity and gravity gradient data. As examples, time varying gravity signals are being used to fine tune ice melt models, biological processes, and of course, geoid change.
Objectives
- Communication between research groups developing novel instruments and the community of gravity scientists
- Coordination of scientific efforts regarding mobile platforms.
- Promotion and coordination in the establishment and measurements of regional gravity networks.
- Organization of scientific workshops and meetings for the discussion of techniques and methods of terrestrial gravity measurements.
Members
Chair: Derek van Westrum (USA)
Vice Chair: Przemyslaw Dykowski (Poland)
Mirjam Bilker-Koivula (Finland)
Sylvain Bonvalot (France)
John Crowley (Canada)
Yoichi Fukuda (Japan)
Silvia Alicia Miranda (Argentina)
Ilya Oshchepkov (Russia)
Wu Shuqing (China)
Hartmut Wziontek (Germany)