SC 1.3: Regional Reference Frames

Chair: Fernand Bale (Cote d’Ivoire)

Terms of Reference

Sub-commission 1.3 deals with the definitions and realizations of regional reference frames and their connection to the global International Terrestrial Reference Frame (ITRF) and International Height Reference Frame (IHRF). It offers a home for servicelike activities addressing theoretical and technical key common issues of interest to regional organizations.

Objectives

In addition to the specific objectives of each regional sub-commission, the main objectives of SC1.3 as a whole are to:

• Coordinate the activities of the regional Sub-commissions focusing on exchange of data, competences and results;
• Promote operation of permanent GNSS stations, in connection with IGS whenever appropriate, as the basis for the long-term maintenance of regional reference frames;
• Promote open access to the GNSS data from permanent stations used for the maintenance of regional reference frames and scientific applications;
• Develop specifications for the definition and realization of regional reference frames, including the vertical component;
• Encourage and stimulate the development of the AFREF project in close cooperation with IGS and other interested organizations;
• Encourage and assist countries, within each regional sub-commission, to re-define and modernize their national geodetic systems, compatible with the ITRF;
• Support the efforts of the United Nations Initiative on Global Geospatial Information Management (UN-GGIM) towards a sustainable Global Geodetic Reference Frame (GGRF).

Program of Activities

• Provide a forum for addressing activities, results and key issues of common interest to the regional sub-commissions;
• Develop analysis strategies and compare methods for the implementation of the regional reference frames and their expression in the ITRF, in full interaction with the IGS;
• Consider developing deformation models that will enable transformation of locations within a defined reference frame between different epochs.

SC 1.3a: Europe (EUREF)

Chair: Martin Lidberg (Sweden)
Secretary: Karin Kollo (Estonia)

Terms of Reference

Sub-commission 1.3a, the regional Reference Frame sub-commission for Europe (EUREF), deals with the definition, realization and maintenance of the European Reference Frames. It is focusing on both the spatial and the vertical components in close cooperation with the pertinent IAG components (Services, Commissions and Inter-commission projects). For more information, see www.euref.eu.

Objectives

• The definition, realization and maintenance of the European Geodetic Reference Systems;
• The promotion and assistance of the adoption and use of European Terrestrial Reference System (ETRS89) and European Vertical Reference System (EVRS) in our partner countries;
• The development and maintenance of the EUREF GNSS Permanent Network (EPN) which is the ground based GNSS infrastructure for scientific and practical applications in positioning and navigation (GGOS, IGS Real-time Service);
• The development of strategies and technologies for the realization of geodetic reference systems.

Structure, Working Groups

Sub-commission 1.3a is composed of representatives from European IAG member countries. The Governing Board is composed of members elected by the EUREF plenary, members in charge of special tasks and ex-officio members. The following Working Groups have been set up:

SC1.3a-WG1: European Unified Height Reference
Chair: Joachim Schwabe (Germany)

• Complement EVRS with an official height reference surface (hybrid quasigeoid model).
• Improve information about national height coordinate frames and their transformations to the EVRS.
• Enhance the usability of the unified European height reference.

SC1.3a-WG2: EPN Densification (EPN-D)
Chair: Ambrus Kenyeres (Hungary)

The primary goal of this WG is to realize a continental-scale, homogeneous, high-quality position and velocity product in a well-defined reference frame, with comparable quality from Greenland to Crete, from Svalbard to Gran Canary. To achieve this goal, processing results (daily or weekly SINEX files) of national or regional GNSS networks are merged using the EPN as backbone in multi-year position and velocity solutions.

SC1.3a-WG3: Deformation models
Chair: Martin Lidberg (Sweden)

The goal of the WG is to develop models of crustal velocities withing EUREF area of interest, based on observed velocities at Continuously Operating GNSS  stationsin the EPN and EPN-D.

SC1.3a-WG4: EPN Reprocessing
Chair: Christof Völksen (Germany)

The purpose of this WG is the coordination of re-processing of GNSS- observationsfrom the EPN when major updates are implemented in scientific GNSS analysis. This typically occurs after major re-analysis by the IGS and release of new ITRFs. Current activity is the third reprocessing of the EPN, aiming for homogeneous time series and reliable velocity estimates following igs2020-standards and compatible with the ITRF2020.

Program of Activities

• Continue to develop the EPN in close cooperation with IGS (International GNSS Service), for the maintenance of the European Terrestrial Reference Frame (ETRF), as a contribution to the ITRF and as an infrastructure to support practical applications for precise positioning and referencing geoinformation;
• Extend the United European Levelling Network (UELN) in order to include as many countries as possible in the current realization of the European Vertical Reference System (EVRS), and further continue the long term maintenance of the European Vertical Reference Frame (EVRF) applying a kinematic approach, in order to take vertical crustal deformations into account;
• Closely follow and contribute to the developments regarding the International Height Reference System (IHRS) and its realizations in International Height Reference Frames (IHRF), and when appropriate establish the precise relation between IHRF and EVRF;
• Promote efforts on regional geoid models in Europe as the link between the ETRF and the EVRF;
• Support new developments in reference frame realization and applications by introducing new technologies like real-time GNSS data transfer and products, as well as Galileo for precise positioning;
• Realize a dense and homogeneous position and velocity product for Europe;
• Establish a dense velocity field model in Europe for the long-term maintenance of the European reference frame;
• Provide GNSS tropospheric estimates at the EPN stations in support of climate research;
• Contribute to the GGOS using the installed infrastructures managed by the EUREF members;
• Promote the adoption of the reference systems defined by EUREF (ETRS89 - European Terrestrial Reference System 1989 and EVRS - European Vertical Reference System) in the European countries and European-wide initiatives related to geo-referencing activities like INSPIRE; 
• Cooperate with European political and scientific organizations and projects, e.g. EuroGeographics, EUMETNET, CEGRN (Central European GPS Geodynamic Reference Network), EPOS (European Plate Observing System), UN-GGIM: Europe, etc.;
• Organize annual symposia addressing activities carried out at national and Europewide levels related to the global work and objectives of EUREF.

Members

The members of the Governing Board at the beginning of 2024 are as follows. New members can be elected. An up-to-date list is available at www.euref.eu.

• Carine Bruyninx (Belgium)
• Rolf Dach (Switzerland)
• Ambrus Kenyeres (Hungary)
• Karin Kollo (Estonia)
• Juliette Legrand (Belgium)
• Martin Lidberg (Sweden)
• Tomasz Liwosz (Poland)
• Benjamin Männel (Germany)
• Rosa Pacione (Italy)
• Martina Sacher (Germany)
• Wolfgang Söhne (Germany)
• Christof Völksen (Germany)
• Joaquin Zurutuza (Spain)

Active honorary members

• Zuheir Altamimi (France)https://sirgas.ipgh.org
• Alessandro Caporali (Italy)
• Markku Poutanen (Finland)
• João Agria Torres (Portugal)

SC 1.3b: South and Central America (SIRGAS)
Chair: José Antonio Tarrío (Chile)
Vice-Chair: Demián Gómez (USA)

Terms of Reference

Sub-commission 1.3b (South and Central America) encompasses the activities developed by the “Geocentric Reference System for the Americas” (SIRGAS). As such, it is concerned with defining, realising and maintaining a modern geodetic reference infrastructure for South and Central America and the Caribbean. This includes a geometric reference frame consistent with ITRS/ITRF and a gravity field-related vertical reference system defined and realized globally. For more information, see https://sirgas.ipgh.org.

Objectives

• To determine, maintain and make available a geocentric reference frame (a set of stations with high-precise geocentric positions and their variation with time) as a regional densification of the global ITRF;
• To support the SIRGAS countries in establishing and maintening national geodetic reference networks as local densifications of SIRGAS in order to guarantee accessibility to the global ITRF at national and local levels;
• To establish a unified vertical reference system supporting the determination and precise combination of physical and geometric heights as well as their variations with time;
• To support the IAG Sub-commission 2.4b (Gravity and Geoid in South America) in activities related to gravity densifications in order to improve the distribution of gravity information and to establish a new Absolute Gravity Network in South America;
• To contribute to the GGOS program by developing and implementing state-of-the art products based on the SIRGAS observational infrastructure;
• To promote, support, and coordinate the efforts of the American and Caribbean countries to achieve these objectives.

Structure, Working Groups

The structure of the Sub-commission 1.3b is based on the functioning SIRGAS Working Groups. They are responsible for implementing the scientific activities and practices approved by the Directing Council. There are currently three WGs:

SC1.3b-WG1: Establishment and maintenance of the Geocentric Reference Frame for the Americas and the Caribbean
Chair: José Antonio Tarrío (Chile)

This WG is responsible for:

• Coordinating the implementation and maintenance of the geocentric reference frame.
• Coordinating its activities at the data centers and its analyses.
• Developing the tools, applications, technical guides and training related to its own activities.

SC1.3b-WG2: National Integration to the SIRGAS Reference Frame
Chair: Demián Gómez (USA)

This WG is responsible for:

• Encouraging the integration of the pre-existing geodetic networks of the Member States to SIRGAS.Developing the tools, applications, technical guides and training for implementing the SIRGAS reference frames.

SC1.3b-WG3: Definition, establishment and maintenance of the Vertical Datum for the Americas and the Caribbean
Chair: Gabriel do Nascimento Guimarães (Brazil)

This WG is responsible for:

• Defining, maintaining and updating a unified system of physical heights.
• Coordinating the implementation of a network of stations linked to the international system for heights.
• Developing and updating a model of a gravimetric, high-resolution geoid.
• Establishing and maintaining an absolute gravity network.
• Developing the tools, applications, technical guides and training related to its own activities.

SC1.3b-WG3 is strongly linked with IAG Sub-commission 2.4b (Gravity and Geoid in South America).

Program of Activities

Since the SIRGAS countries are improving their national reference frames by installing an increasing number of continuously operating GNSS stations, it is necessary to outline the best strategy for the combination of those frames to the continental frame.

This includes:

• Promotion of the IGS and IERS standards within the SIRGAS countries to ensure the adequate installation, maintenance, and analysis of continuously operating GNSS stations;
• Establishment of a SIRGAS National Processing Centre in all the member countries; 
• Refinement of the SIRGAS station hierarchy. At present, two classes are considered: core and densification stations (the establishment of other categories is under consideration);
• Promotion of the adequate usage of SIRGAS as a reference frame using capacity building activities. This comprises SIRGAS schools on reference frames, scientific processing of GNSS data, atmospheric analysis based on the SIRGAS infrastructure, etc.; 
• Promotion and implementation of real-time services based on the SIRGAS infrastructure to make available the reference frame to more users;
• The kinematics of the SIRGAS frame, up to now, have been represented by linear station movements (i.e. constant velocities). This representation is not sufficiently precise due to existing seasonal variations in the station position time series and discontinuities caused by the frequent occurrence of seismic events in the SIRGAS region.

According to this it is necessary

• To model non-linear station movements within the reference frame computation;
• To implement a methodology aiming at a precise transformation between different epochs and, in general, between pre-seismic and post-seismic reference frame realizations in particular;
• To evaluate the feasibility of computing and using near-real-time reference frames instead of those based on epoch station positions and constant velocities.

Members

SIRGAS Executive Committee

• Gustavo Caubarrère (Uruguay); Chair
• Salomão Soares (Brazil); Vice-Chair
• José Antonio Tarrío (Chile); Chair SC1.3b-WG1
• Demián Gómez (USA); Chair SC1.3b-WG2 
• Gabriel do Nascimento Guimarães (Brazil); Chair SC1.3b-WG3

SIRGAS Directing Council

for an up-to-date list, see https://sirgas.ipgh.org.

SIRGAS Scientific Council

• Denitzar Blitzkow (Brazil)
• Laura Sánchez (Germany)
• Hermann Drewes (Germany)
• Claudio Brunini (Argentina)
• María Virginia Mackern (Argentina)
• Luiz Paulo Souto Fortes (Brazil)
• Sílvio Rogerio Correia de Freitas (Brazil)
• Melvin Jesús Hoyer Romero (Venezuela)

SC 1.3c: North America (NAREF) Co-Chairs: Jason Bond (Canada) and Phillip McFarland (USA)

Terms of Reference

Sub-commission 1.3c intends to provide international focus and cooperation for issues involving the horizontal, vertical, and three-dimensional geodetic control networks of North America, including Greenland (Denmark). For more information, see www.naref.org.

Objectives

In collaboration with the IAG community, its Services and the national geodetic organizations of North America, the objectives of Sub-commission 1.3c are:

• Densification of the ITRF in North America and promotion of its use;
• Definition, maintenance and future evolution of plate-fixed geometric reference frames for North America, including the North American Datum of 1983 (NAD83) and the forthcoming North American Terrestrial Reference Frame of 2022 (NATRF2022);
• Effects of crustal motion, including post-glacial rebound and tectonic motions along, e.g., the western coast of North America and in the Caribbean;
• Coordination of efforts with neighboring SC1.3b South and Central America (SIRGAS) to ensure strong ties between each other’s reference frames;
• Outreach to the general public through focused symposia, articles, workshops and lectures, and technology transfer to other groups.

Working Groups, Program of Activities

There are currently the following Working Groups:

SC1.3c-WG1: North American Reference Frame Densification (NAREF)
Chair: Jason Bond (Canada)

This WG is responsible to densify the ITRF in the North American region by organizing the computation of weekly coordinate solutions and associated accuracy information for continuously operating GNSS stations that are not part of the current IGS global network. A cumulative solution of coordinate and velocities will also be determined on a weekly basis. The WG will organize, collect, analyze and combine solutions from individual agencies, and archive and disseminate the weekly and cumulative solutions.

SC1.3c-WG2: North American Terrestrial Reference Frame of 2022 (NATRF2022)
Chair: Rick Bennett (USA)

This WG is responsible to establish a high-accuracy, geocentric reference frame, including velocity models, procedures and transformations, tied to the stable part of the North American tectonic plate which would replace NAD83 and serve the broad scientific and geomatics communities by providing a consistent, mm-accuracy, stable reference with which scientific and geomatics results (e.g., positioning in tectonically active areas) can be produced and compared.

SC1.3c-WG3: Reference Frame Transformations in North America
Chair: Michael Dennis (USA)

This WG is responsible to determine consistent relationships between international, regional and national reference frames in North America, to maintain (update) these relationships as needed and to provide tools for implementing these relationships.

Members

• Phillip McFarland (USA); Co-Chair
• Jason Bond (Canada); Chair SC1.3c-WG1; Co-Chair
• Rick Bennett (USA); Chair SC1.3c-WG2
• Michael Dennis (USA); Chair SC1.3c-WG3
• Mike Bremner (Canada)
• Mohammad Ali Goudarzi (Canada)
• Mike Piraszewski (Canada)
• Finn Bo Madsen (Denmark)
• Dan Gillins (USA)
• Dan Roman (USA)
• Jarir Saleh (USA)
• Dru Smith (USA)
• Michael Craymer (Canada)
• Mike Bevis (USA)
• Geoff Blewitt (USA)
• Jeff Freymueller (USA)
• Tom Herring (USA)
• Corné Kreemer (USA)
• Richard Snay (USA)

SC 1.3d: Africa (AFREF)

Chair: Elifuraha Saria (Tanzania)

Terms of Reference 

Sub-commission 1.3d (Africa) is concerned with the definition and realization of a unified continental reference frame (AFREF) for Africa, which will be consistent and homogeneous with the global ITRF.

Objectives

In collaboration with the IAG community and its Services, regional organizations, and the National and Regional Mapping Organizations of Africa, the objectives of Sub-commission 1.3d (Africa) are:

••

Program of Activities complete for AFREF!

•••

Members preliminary

• Elifuraha Saria (Tanzania); Chair
• Emanuel Nkurunziza (Kenya)
• Joseph Dodo (Nigeria)
• Salah Mahmud (Egypt)
• Cesare Mbaria (Kenya)
• Prosper Ulotu (Tanzania)
• Andre Nonguierma (Burkina Faso)
• Akingbade O (Nigeria)
• Moha El-Ayachi (Morocco)
• Elias Lewi (Ethiopia)
• Patrick Vorster (South Africa)
• Kamal Labbassi (Morocco)

Active honorary members

• Richard Wonnacott (South Africa)
• Hussein Farah (Kenya)
• Olajide Kufoniyi (Nigeria)

SC 1.3e: Asia-Pacific (APREF)

Chair: Basara Miyahara (Japan)

Terms of Reference

Sub-commission 1.3e aims to improve regional cooperation that supports the realization and densification of the ITRF. This activity will be carried out in close collaboration with the Geodetic Reference Framework for Sustainable Development Working Group of the United Nations Global Geospatial Information Management for Asia and the Pacific (UN-GGIM-AP). For more unformation, see https://un-ggim-ap.org/wg/working-group-1-geodetic-reference-frame.

Objectives

• Densification of the ITRF and promotion of its use in the Asia Pacific region;
• To encourage the sharing of GNSS data from Continuously Operating Reference Stations (CORS) in the region;
• To develop a better understanding of crustal motion in the region;
• To promote the collocation of different measurement techniques, such as GNSS, VLBI, SLR, DORIS and tide gauges, and the determination and maintenance of precise local tie vectors among these geodetic techniques at these sites;
• To provide capacity development opportunities to developing countries through symposia, workshops, seminars, training courses, and technology transfer activities.

Program of Activities

The activities of this Sub-commission will principally be those of the Asia-Pacific Reference Frame (APREF) project. This is a joint project between IAG SC 1.3e and the geodetic working group of UN-GGIM-AP and consists of a Central Bureau, Network operators, Data centers and Analysis centers. The Central Bureau is at Geoscience Australia and functions as the “day-to-day” APREF coordinating body. Specifically, the Central Bureau ensures that APREF products are made available to the global geodetic community.

Furthermore, they are the Combination Centers responsible for analyzing, combining and validating the individual solutions of the contributing Analysis Centers, and for expressing the combined solution in the ITRF.

The resulting APREF data and products have an open access data policy via the internet following the practice of the International GNSS Service (IGS). They consist of daily GNSS RINEX data, station log-files, weekly coordinate estimates in SINEX format, and APREF network and time-series plots. For more details, see https://www.ga.gov.au/scientific-topics/positioning-navigation/geodesy/asia-pacific-reference-frame.

Members

The members of the SC 1.3e are national geodetic representatives from the UN-GGIMAP member nations and APREF participating organizations.

1. UN-GGIM-AP WG1 (Geodetic Reference Frame)

• Basara Miyahara (Japan); Chair
• Guorong Hu (Australia); Vice-Chair
• Yamin Dang (China)
• Asakaia Tabua (Fiji)
• Upendra Nath Mishra (India)
• Sidik Tri Wibowo (Indonesia)
• Seyed Abdoreza Saadat Mirghadim (Iran)
• Ahmad Sanusi bin Che Cob (Malaysia)
• Dalkhaa Munkhtsetseg (Mongolia)
• Nic Donnelly (New Zealand)
• Jongsin Lee (South Korea)

2. APREF Analysis Group

• Guorong Hu (Australia)
• Alex Woods (Australia)
• Yunbin Yuan (China)
• Basara Miyahara (Japan)

SC 1.3f: Antarctica

Chair: Martin Horwath (Germany)

Terms of Reference

Sub-commission 1.3f focuses on the realization and densification of a unified reference frame for Antarctica, which will be consistent with the global ITRF. The Sub-commission shares objectives and activities of the Scientific Committee on Antarctic Research (SCAR), namely of the SCAR Expert Group Geodetic Infrastructure of Antarctica (GIANT). The Sub-commission closely links IAG and SCAR activities by embedding identical activities (with identical persons where indicated) into the two complementary organizational structures.

Objectives

• Maintenance and densification of the precise geodetic reference network in Antarctica by permanent observations and GNSS campaigns;
• Realization of a unified vertical datum including GNSS ties of tide gauges;
• Providing unified reference for further GNSS applications like airborne gravimetry, ground truthing for satellite missions, geodynamics and glaciology;
• Develop technologies for remote geodetic observatories;
• Stimulate and coordinate international collaboration on the above fields, under the unique political conditions of Antarctic research given by the Antarctic Treaty, in order to make optimum use of logistics and infrastructure.

Program of Activities

• Organization of GNSS campaigns in Antarctica;
• Extend activities for the operation of remote permanent GNSS stations;
• Maintenance of the data archive (SCAR GNSS data base) to collect Antarctic GNSS data and provide them to the scientific community;
• Data analysis and determination of the Antarctic GNSS network as a regional densification of ITRF;
• Provide homogeneous site velocities for e.g. glacial iso-static adjustment determination;
• Support airborne surveys and satellite missions with precise terrestrial reference;
• Collaborate with IAG Sub-Commission 3.4 (Cryospheric Deformation) and the SCAR Scientific Research Programme Solid Earth Response and Influence on Cryosphere Evolution (SERCE) and subsequent programmes, respectively;
• Organize special workshops on the consistent analysis of GNSS data and realization of ITRF;
• Organize meetings/sessions at conferences like IAG, IUGG, SCAR Open Science Conference.

Members

• Martin Horwath, (Germany); Chair
• Yuichi Aoyama (Japan)
• Manuel Berrocoso (Spain)
• Alessandro Capra (Italy)
• Dave Collett (New Zealand)
• Rene Forsberg (Denmark)
• Thomas James (Canada)
• Aspurah Kamburov (Bulgaria)
• Hannu Koivula (Finland)
• Matt King (Australia)
• Kenichi Matsuoka (Norway)
• Alexey Matveev (Russia)
• Gennadi Milinevsky (Ukraine)
• Elizabeth Petrie (United Kingdom)
• Goncalo Prates (Portugal)
• Mirko Scheinert (Germany)
• Norbertino Suarez (Uruguay)
• Terry Wilson (USA)
• Andres Zakrajsek (Argentina)