the progress of international geodesy after world war ii

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The Progress of International Geodesy after World War IIand the involvement of Wolfgang Torge and Günter Seeber

Festive Colloquium, Institute of Geodesy, Leibniz University Hannover, June 8, 2021

Hermann DrewesTechnical University of Munich

Honorary Secretary General of theInternational Association of Geodesy

References

2H. Drewes, The progress of international geodesy after World War II, Leibniz University Hannover, June 8, 2021

My presentation will be aligned to the structure of the IAG, which may change at the General Assemblies.The detailed research programme is published in the quadrennial “Geodesist’s Handbook” at Springer-Verlag, the reports of the past four years in the IAG Reports (Travaux), both online available at https://office.iag-aig.org.

785 pp343 pp

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Status of International Geodesy after World War II

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Dec. 1945: International Union of Geodesy and Geophysics (IUGG) Executive Committee meeting in Oxford, UKJuly 1946: Extraordinary IUGG General Assembly in Cambridge, UKAug. 1946: International Association of Geodesy (IAG) Permanent Commission meeting in Paris, FranceAug. 1948: IUGG/IAG General Assembly in Oslo: Decision on a topical structure in 5 Sections

(before there were project-based Commissions)

H. Drewes, The progress of international geodesy after World War II, Leibniz University Hannover, June 8, 2021

Triangulation Precise Levelling Geodetic Astronomy Gravimetry Geoid Connection of

national networks Adjustment of large

networks Length calibration

lines, Väisäläcomparators

Electro-optical distance measure-ments: trilateration

Reduction of atmo-spheric refraction (elementary models)

Surface gravity reduction along levelling lines

Height variations in time detected from repeated levellings

Methods for azimuth, latitude and longitude determination

Zenith camera measurements

Clock corrections (master clock in laboratory)

Global gravimetricnetwork as a main challenge of IAG

Absolute pendulum measurements

Establishment of internat. gravimetric networks

Gravimetric calibration lines

Collection of worldwide gravity measurements

Determination of defections of the vertical

Terrain corrections Gravimetric geoid

determinations

1946 ff.: Triangulation


1947: ● Order of the US Army Map Service (AMS) for creating a unified European triangulation network

● IAG was reluctant to participate in a military project and took part of the work conditionally

1950: First completion by adjustment of triangulation chains (European Datum 1950, ED50)

1951: Decision of IAG for scientific continuation (not for military purposes)

1954: IAG Commission “RETrig”: joint adjustment of complete national networks (not only triangulation chains)

1979: Completion of phases 1 and 2 (ED79)

1987: Completion of phase 3 (ED87) including TRANSIT Doppler observations, SLR and VLBI stations. (Kobold 1980, Ehrnsperger 1991)

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1946 ff.: Levelling

Unified European Levelling Network1948: Suggestion of Tauno Kukkamäki (Finland) to connect all the national levelling networks in Europe.1954: IAG Resolution in Rome to establish a commission for the “United European Leveling Network” (UELN).

● Common adjustment of geopotential differences.● Separate computation of the northern block because of postglacial rebound.

1963: Final report (temporary end, continued 1971)

Atmospheric refraction in spirit levelling Studies started already in the International Geodetic Association (Internationale Erdmessung) end of the 19th century.However, it was still a theme 80 years later, when height changes at Palmdale, California, from repeated levellings were misinterpreted due to the missing reduction of the atmospheric refraction. (W. E. Strange, JGR 86, 2809-2824, 1981).

(Lallemand 1896)

Wolfgang Torge dealt with this topic in his publication (1965) on systematic and random errors in levellings, and he emphasized the importance for the Palmdale problem at the 9th GEOP conference in Columbus, Ohio, 1978.

H. Drewes, The progress of international geodesy after World War II, Leibniz University Hannover, June 8, 2021 5

1946 ff.: Geodetic Astronomy


Geodetic astronomic observations were mainly used for Determination of local geodetic datums (Laplace stations: astronomic latitude, longitude and azimuth) Determination of deflections of the vertical for triangulations, Determination of deflections of the vertical for astro-geodetic geoid determinations.

Example of geocentric offsets [m] of South American datums

Datum Country ΔX ΔY ΔZProvisional South American PSAD 1956

Bolivia, Chile, Ecuador, Peru,Venezuela

-288 175 -376

Córrego Alegre 1961 Brazil -206 172 -6Chua Astro Paraguay -134 229 -29Provisional Chile 1963 South Chile 16 196 63Campo Inchauspe 69 Argentina -148 136 90S. American SAD 69 All S. America -57 1 -41Bogotá 1975 Colombia 307 304 -318(Caddess et al. 1993)

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1946 ff.: Gravimetry


Pendulum measurements, international and national gravimetric networks (from Kneissl 1956)German Gravity Network 1962

1946 ff.: Geoid Determination


- Gravimetric method (Stokes integration and spherical harmonics)- First global computation (isostatic model): Hirvonen 1934- Global computations (Stokes integration, 5°×5°-blocks): Tanni 1948- “Columbus-Geoid“ (free air anomalies): Heiskanen 1957- “Uotila’s geoid” (spherical harmonics of fourth degree): Uotila 1962

Uotila’s geoid 1962, f=1:298,24, (from Heiskanen & Moritz 1967)

Columbus geoid for Europe (Internat. ellipsoid f=1:297, Heiskanen 1957)

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Berkeley 1963: Inception of the Space Age in Geodesy


1946 Triangulation↓

Levelling↓

Geodetic Astronomy↓

Gravimetry↓

Geoid↓

GeodeticPositioning

Levelling and Crustal Motion

Geodetic Astronomy & Artificial Satellites Gravimetry Physical Geodesy

Continental networks (e.g. Australia 1966, Europe RETrig-FO,S. America SAD 69)

Electronic distance measurements

Geometric satellite observations and satellite triangulation

Reduction of atmo-spheric refraction (improved models)

Geopotential num-bers instead of (orthometric or normal) heights

Analysis of vertical surface movement (deformation, time dependent heights)

Transition from geodetic astronomyto satellite geodesy

Methods for the determination of satellite orbits (geo-metric, dynamic)

Global gravimetricnetwork

Dynamic satellite orbit determination requires improved gravity models

Collection of worldwide gravity

Gravity potential models by spherical harmonics

Geodetic ReferenceSystem (GRS 67)

The 1960s: Geodetic Astronomy and Artificial Satellites


(Ø 30 m)

Wild BC-4

chamber

Optical balloon satellitesEcho 1: 1960-08-12Echo 2: 1964-01-25PAGEOS: 1966-06-24

(Ø 30 m)

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The 1960s: Geodetic Positioning from Satellite Triangulation


The optical network is based on the BC-4 camera observations at 45 global stations. It connected for the first time all the continents providing geocentric station coordinates all over the Earth. The accuracy ranged from ±2 m to ±8 m (ø 4.5 m). (Schmid, 1974).

Worldwide geometric three-dimensional satellite triangulation

Günter Seeber’s PhD thesis (1972) is on the stochastics of photo-optically estimated star and satellite coordinates.

(Schmid 1974)

The 1960s: Positioning from Satellite Doppler Observations


Doppler Satellite TRANSITNetwork (TRANET) Transit 1A: 17.09.1959 failTransit 1B: 13.04.1960…Transit O-11: 27.10.1977~30 satellites of the first generation got into orbit.

(Seeber 1988)

Günter Seeber worked on the installation of the satellite observation station in Todenfeld close to Bonn, Germany.

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The 1960s: Levelling and Crustal Motion


1960: IAG Commission on Recent Crustal Movements (CRCM)1963: IAG Resolution on

the compilation of a world map of crustal movements, especially as the first step for Eastern Europe, Western Europe, Fennoscandia, and North America,

The study of continental drift by means of astronomical and geodetic methods,

Levelling in Switzerland (Pavoni and Green 1975)

Tide gauges in Fennoscandia (Kakkuri 1985)

6030

0

mm

The 1960s: Gravimetry


International Gravity Standardization Net IGSN71 (Morelli 1974)Gravimetric observations from 1950 to 1970: 1854 points, approx. 10 absolute and ~ 25000 relative measurements

Offset of 14 mGal in the Potsdam gravity system value manifested.

Torge 1975

Wolfgang Torge’s PhD thesis (1966) is on the network from North Cape (Norway) to the equator (Congo). It was extended 1964-1970 to Cape Town (South Africa).

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The 1960s: Physical Geodesy


Geodetic Reference System from 1924 to 1967 1924/1930: First Geodetic Reference System based on the theory of global level ellipsoids with terrestrial data:

- a, f from isostatically reduced astrogeodetic data in USA (Hayford 1909), “International Ellipsoid“- γ0 from isostatically reduced gravity data (Heiskanen 1928),

using the iInternational gravity formula (Cassinis 1930). 1967/1971: First inclusion of space geodetic data

- Semimajor axis from globally collected astrogeodetic observations,- Gravitational constant (GM) from space probes,- Dynamic form factor (J2) from satellite.

Semimajor axis a Flattening f Normal gravity γ0 Rotation velocity ωInternat. ellipsoidIUGG 1924/1930 6 378 388 m 1 : 297.0 9.780 490 m s-2 7.292 115 ∙ 10-5 rad s-1

GRS 67IAG 1967/1971 6 378 160 m 1 : 298.3 9.780 318 m s-2 7.292 115 ∙ 10-5 rad s-1

GRS 80IAG 1979/1983 6 378 137 m 1 : 298.257 222 101 9.780 326 7715 m s-2 7.292 115 ∙ 10-5 rad s-1

Moscow 1971: Space Techniques and Interpretation of Results


1963: Geodetic Positioning



↓Control Surveys

↙Space Techniques

↙Gravimetry Theory and

EvaluationPhysical

Interpretation

Horizontal and vertical positioning

Continental datumnetworks including Doppler campaigns (ED79, NAD83)

WGS-72 including TRANSIT-Network

Extended fromsatellites to VLBI

Satellite LaserRanging (Starlette, Lageos)

Satellite RadarAltimetry (GEOS-C)

Improvement of terrestrial methods (absolute gravity meters)

Dynamic satellite methods require global gravity field

Global models SAO, GEM, GRIM

Potential theory Optimization of

geodetic networks Statistical methods

(Collocation, Least squaresprediction)

Adjustment with large equation systems

First step towards geokinematics andgeodynamics

Earth tide models Geodetic Reference

Systems (GRS 80) Geoid determination

↙

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The 1970s: Control Surveys (Horizontal Networks)


“Revolution” in global and continental networks due to space techniques: Optical sat. triangulation ± 4 m Doppler measurements ± 0.4 m Satellite Laser Ranging ± 0.04 m 2000’s SLR and VLBI ± 0.004 m1970’s Doppler campaigns worldwide:Europe: EDOC 1 & 2Africa: ADOSAustralia: entered into AGD84North America: entered into NAD83Global system: entered into WGS72Günter Seeber supervised a PhD Thesis on the effect of Doppler stations in local triangulation networks: ± 2 m → ± 0.5 m

(Hoyer 1982)

Error ellipses of Venezuelan triangulation

Error ellipses triangulation plus Doppler

1 m 1 m

The 1970s: Control Surveys (Vertical Networks)


Vertical control in Europe:IUGG and IAG Resolutions 1954, 1963, 1967 and 1971 to establish and to continue with the “United European Levelling Network” (UELN)1963 final report of the first phase (see above)Western Europe:1971 reactivation of the collection of data and

adjustment procedures: 2 computing centres (Delft and Munich)

1981 preliminary adjustment (without northern countries because of post glacial uplift)

1986 final adjustment UELN-73/8614 countries, 774 nodal points, 1083 lines

Eastern Europe:1973 Map of recent crustal movements 1974 – 1978 Relevelling in Eastern Europe

(Uniform Precise Levelling Network, EPNN) (Augath& Ihde)

AlicanteAmsterdamAntalyaCascaisConstantaGenovaHelsinkiKronstadtMalin HeadMarseilleNewlynOstendeTregdeTriesteNo informOther

European height datums

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The 1970’s Space Techniques: Global LAGEOS Tracking Sites


SLR: Satellite laser ranging network in the early 1980s.Precision (< 10 cm) is hundredfold better than the previous satellite triangulation and ten times better than the Doppler measurements.

(Christodoulidis et al., 1984)

The 1970s: Gravimetry


Gravity changes with timeBecause of the substantial improvement of the precision of relative gravity measurements, e.g. the LaCoste and Romberg gravimeters, it became possible to observe small gravity changes with time, e.g. due to tectonic or sedimentary vertical crustal deformation. Those projects were initiated in all continents.

Wolfgang Torge conducted various projects in Europe and South America.

Example: Gravimetry changes in the tectonic zone in Island (plate boundary of North America and Eurasia plates)

10-7 m s-2

Neotectonic zoneNorth American plate Eurasian plate

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The 1970s: Theory and Evaluation


Potential theory, sampling-functions, splines, ...- Theory of linear spaces (vectors, quaternions, matrices, tensors, Hilbert-spaces, ..)- Mathematical structure and differential geometry of the gravity field,- Free, fixed, and mixed boundary value problems,- Convergence problems in Physical Geodesy,- Representation of the gravity field by splines.

Geodetic observation equations, collocation- Statistical methods for estimating and testing of geodetic data,- Variance-covariance component estimation,- Optimization of geodetic networks,- Elimination methods, iterative and intrinsic methods- Least squares prediction.

Adjustment of large networks using electronic computers- Theory of geodetic networks (variance-covariance matrices),- Datum definition,- Solution of large equation systems (e.g. organization of memory capacity),- Use of computer systems for organizing geodetic data (database systems),- Solution for large networks (>500 points) at one fell swoop, weighting, datum (Laplace points), e.g. NAD83.

The 1970s: Physical Interpretation


2 IAG Commissions in Section V “Physical Interpretation”: Earth Tides Recent Crustal Movements (CRCM), see 1960’sThere were many Earth tide observation stations all over the world in order to estimate the amplitudes and phase lags of the relevant tidal waves.

The World Data Center for Earth Tides in Brussels collected those data and published tidal parameters and maps particularly for Western Europe (figure right).

Amplitude factor (left) and phase lag (right) for the M2 wave (Ducarme et al. 1980).

Wolfgang Torge installed various of such stations in Europe, Asia and South America.

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Hamburg 1983: Geodynamics Research(The General Assembly was organized by Wolfgang Torge)


1971: Control Surveys Space Techniques Gravimetry Theory and

EvaluationPhysical

Interpretation↓

Positioning↓

Advanced Space Techniques

↓Determination of the

Gravity Field

↓General Theory

and Methodology

↓Geodynamics

Continental networks

Applications to engineering

Marine positioning Vertical reference

systems Global Positioning

System (GPS)

Coordination of space techniques for geodynamics (CSTG)

Lunar laser ranging Satellite-to-satellite

tracking & satellite gradiometry

Atmosphere effects in space measures

Satellite altimetry

International Gravity Commission (IGC)

International GeoidCommission (IGeC)

Bureau GravimetriqueInternational (BGI)

Comparison of relative and absolute gravimetry

New world absolute gravity network

Differential geometry of the gravity field

Boundary value and convergence

Statistic methods for geodetic data

Geodetic data base management

Time dependent positioning

Earth Tides (ICET) Recent Crustal

Movements (CRCM) NASA Crustal Dyna-

mics Project (CDP)

The 1980s and 1990s: Positioning – Continental networks


With the availability of sufficient GPS observation stations, continental reference frames were established. The IAG Commission X “Continental Networks”, before structured in triangulation and levelling networks, installed in 1987 the European Reference Frame (EUREF) as the first Sub-commission concentrating on “space geodesy sites”. In the following years, GPS-based reference frames were established in all the continents.

In 1991, Wolfgang Torge became IAG President. At the General Assembly in Beijing 1993, he initiated the South American Reference System (SIRGAS). A GPS campaign was organized in 1995 with receivers from many countries. Günter Seeber contributed significantly to the observations and methodology.

SIRGAS Kick-off meeting, Buenos Aires 1994

Opening by Wolfgang Torge, discussing the methodology with Günter Seeber

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The 1980s and 1990s: Advanced Space Techniques


Satellite AltimetryThe first operational altimetry satellite was launched in 1975: Geodynamics Experimental Ocean Satellite GEOS-3. 1978 followed SEASAT-A, 1985 GEOSAT, 1991/95 ERS-1/2, 1992 TOPEX-Poseidon.

(Savcenko 2005)

The data analysis allowed already in an early stage the precise quantification of sea level variations and the awareness that the sea level rise is not constant but has periodic signals from annual to decades.

The 1980s and 1990s: Determination of the Gravity Field


Smithsonian AstrophysicalObservatory (SAO)- SAO SE 80 (1980)

Goddard Space Flight Center (GSFC)- GEM-10B (1981), - GEM-T3 (1992)

GRGS Toulouse / DGFI München/GFZ Potsdam: - GRIM3 (1983),- GRIM4 (1992), - GRIM5 (2000)

NIMA / GSFC / OSU:- EGM96 (1998)

GRIM3 (Reigber, Balmino, Moynot, Müller 1981)

Series of global gravity models of various institutions

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The 1980s and 1990s: Gravimetry


22 absolute gravimetry stations in S. America (Torge et al. 1994)● Absolute Gravity Basestation Network

The 1980’s were the time when absolute gravimetry with free-fall gravimeters started.Wolfgang Torge with the team of the Institute of Geodesy in Hannover was one of the first active in this field. They performed measurements in Europe, Asia and South America.

JILAG-3 in Maracaibo, Venezuela

The 1980s and 1990s: General Theory and Methodology


1984: Working Group “Theory of Geodetic Reference Frames”

ITRF88 (after Boucher and Altamimi 1989)

Bureau International de l’Heure (BIH) collected SLR station position solutions 1987: Transition from BIH to International Earth Rotation Service:Birth of the ITRF1988: Initial ITRF with station positions only, velocities were taken from the geophysical plate model AM0-2 (Minster & Jordan 1978)

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The 1980s and 1990s: Geodynamics


APKIM: Actual Plate KInematic Models

For the first time, it was possible to compare geophysical and geodetic models of tectonic plate motions.

No Year Stat. Plat.1.1 1988 29 32.1 1989 70 63.1 1991 94 64.1 1992 110 57.0 1996 167 78.0 1997 305 129.0 1999 346 12

- - - APKIM3.1 ── Minster and Jordan AM0-2

The 1980s and 1990s: Regional Deformation Models


1979: NASA Crustal Dynamics Project (CDP) with emphasis on the Mediterranean Laser Network (MEDLAS)

1991: Observed and interpolated velocities 1999: Deformation of the Persia-Tibet-Burma orogenic belt

Eurasian Plate

African Plate

Eurasian Plate

Arabian Plate

Indian Plate

Amur Plate

YantzePlate

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Sapporo 2003: Completely New Structure


CommissionsCommissions represent major fields of activity in the IAG which, together, cover the whole of geodesy. They areReference Frames Gravity Field Earth Rotation and Geodynamics Positioning and Applications

Inter-Commission Committee on TheoryThe mission of the ICCT is to interact directly with other IAG entities, in particular Commissions and GGOS.:

Global Geodetic Observing SystemThe Global Geodetic Observing System (GGOS) works with the IAG Services to provide the geodetic expertise and infrastructure necessary for the monitoring of the Earth system and global change research.

ServicesServices collect and analyze observations for products relevant to geodesy and other sciences and applications.

IERS IDS IGS ILRS IVS IGFS BGI ICET ICGEM IDEMS IGeS PSMSL IAS IBS

Association Components are Commissions, Services, the Global Geodetic Observing System (GGOS), the Inter-Commission Committee on Theory, and the Communication and Outreach Branch (COB).

2003 ff.: General Structure of Commissions


Reference Frames Gravity Field Earth Rotation and Geodynamics

Positioning and Applications

Inter-Commission Committee on Theory

Coordination of space techniques

Global referenceframes

Regional reference frames

Interaction of celestial and terrestrial frames

Vertical reference frames

Gravimetry and gravity networks

Spatial & temporal gravity field & geoid

Satellite gravity missions

Regional geoid determination

Satellite altimetry Gravity and mass

transport Geoid and physical

height systems

Earth tides and geodynamics

Crustal deformation

Earth rotation and geophysical fluids

Cryospheric deformation

Tectonics and earthquake geodesy

Multi-sensor systems

Multi-constellationGNSS

Positioning tech-nologies & GNSS augmentation

Geodesy in Engineering

Remote sensing of the atmosphere

Satellite and airborne imaging systems

The Inter-Commission Committee on Theory is structured in Joint Study groups together with all Commissions. From 2003 up to date these were more than 50 Study Groups on all themes, arising in general in more than one Commission.

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2003 ff.: Reference Frames (global)


The International Terrestrial Reference Frame (ITRF) is computed by three ITRS Combination Centres (IGN France, DGFI Germany, JPL USA), the Product Centre being at IGN. The methodology is jointly discussed by the Commission “Reference Frames”, and the IERS Convention Centre. Data are provided by IERS Technique Centres IDS, IGS, ILRS, IVS.Recent ITRFs are: ITRF2005, ITRF2008, ITRF2014.

Altamimi et al. 2016

The data have to be re-analysed for each ITRF. One reason are the varying GNSS antenna phase centres. Günter Seeber developed an antenna calibration robot, which is used for official calibrations of the GNSS antennae.

ITRF2014

2003 ff.: Reference Frames (regional)


Regional GNSS reference frames are computed continuously

www.epncb.oma.bewww.sirgas.org

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2003 ff.: Gravity Field


The Gravity Recovery and Climate Experiment (GRACE) was a joint mission of NASA and the German Aerospace Center (DLR). The twin satellites took measurements from its launch in March 2002 to the end of its science mission in October 2017. The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) is a continuation launched in May 2018.

The data analysis showed for the first time global gravity variations with very high resolution in space and time. The interpretation allows statements about mass displacements in the fluid, solid, and gaseous Earth.

Ramillien 2015

2003 ff.: Height and Gravity Reference Systems


IAG Resolutions 2015 on the definition and realisation of an International Height Reference System (IHRS) and the establishment of a global Absolute Gravity Reference System, and 2019 on the establishment of the International Height Reference Frame (IHRF) and the infrastructure of the International Gravity Reference Frame.

Draft of the IHRF (Sánchez 2018)

More than 1200 absolute gravity stations (http://agrav.bkg.bund.de/agrav-meta/)

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2003 ff.: Earth Rotation and Geodynamics


Polar motion 1900-1929 (left), 1960 – 1980 (middle), and 1980 – 2003 (right)

Space techniques allow an extremely precise representation of the variable Earth rotation. The interpretation provides the knowledge of the dynamics of the Earth system with its solid, fluid and gaseous components.

The IERS publishes the time dependent Earth orientation parameters (EOP).

2003 ff.: Positioning and Applications


www.gfz-potsdam.de

Remote sensing of the atmosphere:Application of GNSS measurements for regional high-resolution (hourly) ionosphere models

April 2013 December

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IAG Services


Name (bold = at present active in IAG) Abbr. Founded RemarkBureau International des Poids et Mesures BIPM 1875International Bibliographic Service IBS 1889 / 1984 re-establishedInternational Latitude Service / Internat. Polar Motion Service ILS / IPMS 1899 / 1962 1987 into IERSBureau International de l‘Heure BIH 1912 1987 into IERSPermanent Service of Mean Sea Level PSMSL 1933Bureau Gravimetrique International BGI 1951International Center for Earth Tides ICET 1956 2015 into IGETSInternational Earth Rotation (and Reference Systems) Service IERS 1987 (2003) (change of name)International (Geoid Service) Service for the Geoid (IGeS) ISG 1992 (2014) (change of name)International GPS (GNSS) Service IGS 1994 (2005) (change of name) International Laser Ranging Service ILRS 1998International VLBI Service for Geodesy and Astrometry IVS 1999International Digital Elevation Models Service IDEMS 1999International Center for Global Earth Models ICGEM 2003International DORIS Service IDS 2003International Gravity Field Service IGFS 2004International Altimetry Service IAS 2008International Geodynamics and Earth Tide Service IGETS 2015

IAG’s Global Geodetic Observing System (GGOS)


The Global Geodetic Observing System (GGOS) works with the IAG components in advancing our understanding of the dynamic Earth system by quantifying our planet’s changes in space and time.

GGOS was established by the IAG Executive Committee and the IAG Council, and endorsed by an IUGG Resolution during the IUGG General Assembly 2003.

The principal components are GGOS Coordinating Office Bureaus of Networks & Products GGOS Focus Areas

For details see https://ggos.org/

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Summary of the IAG Structure since 1946

Section I / Commission 1

Section II / Commission 2

Section III / Commission 3

Section IV / Commission 4

Section V / Inter-Com. Committee

1946 Paris1948 Oslo Triangulations Precise Levelling Geodetic Astronomy Gravimetry Geoid

1963Berkeley

Geodetic Positioning



1983Hamburg Positioning

Advanced Space Techniques

Determination of the Gravity Field

General Theory and Methodology Geodynamics

2003Sapporo

Reference Frames

Gravity Field Earth Rotation and Geodynamics

Positioning and Applications

Inter-Commission Comm. on Theory

IAG Services and the Global Geodetic Observing System (GGOS)


2023Berlin

2020: Discussion on the IAG Structure in a Committee of the IAG Executive Committee.Do we need a new structure to meet the scientific and societal challenges of the future?

Thoughts About Future Geodetic Research


There were several revolutionary changes in recent time affecting geodesy significantly: Space techniques for positioning, gravity field and geodynamics affecting all applications; Precise clocks converting geodetic observations to precise time measurements for geometry and gravity; Powerful computers to analyse the enormous amount of data; The Internet to communicate the data quickly worldwide.

Future challenges are, e.g., the climate change, preservation of oceans and waters, and new technologies.

In order to meet these challenges of science and practice, the IAG introduced 2019 new components: Inter-Commission Committee for Climate Research (ICCC):

Climate signals in geodetic measurements; improve numerical climate models and climate monitoring systems; Inter-Commission Committee on Marine Geodesy (ICCM):

Sea floor monitoring, ocean tides analysis, ocean surface (geoid) studies, undersea navigation; Project Novel concepts and quantum technology (QuGe):

Atom interferometry, Laser interferometric ranging in space, optical clocks for measuring gravity potential differences (general theory of relativity);

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Conclusions and Outlook


Geodesy has traditionally a leading role for scientific and practical progress, e.g.1875: Meter convention (Bureau International des Poids et Mesures, BIPM)1883: Greenwich Meridian as the longitude reference (Washington 1884) 1912: Bureau International de l’Heure (BIH): Universal Time (UT)1933: Permanent Service of Mean Sea Level (PSMSL) important for monitoring sea level rise1987: International Earth Rotation and Reference Systems Service (IERS) for unique positioning in practice1994: International GNSS Service (IGS): Satellite orbits for all positioning and navigation

We have to publicise the information to politicians and society, e.g., that any navigation system, in means of transport or mobile telephone, uses the satellite orbit data provided by the IGS for free. They have to know that all positioning of borders, engineering constructions, topographic maps etc. get the necessary data from geodesy.

The text books of Wolfgang Torge on Geodesy and Gravimetry, and Günter Seeber on Satellite Geodesy are broadly spread among students all over the world. They are advertising geodesy. Many thanks to them!

Geodesy is connecting the Earth and the universe by quantifying changes in time and space from observations and models including their reliability.

Let us continue our work for the collective good of science and society!


Thank you very much for your

attention!

the progress of international geodesy after world war ii

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