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1.
《Journal of Geodynamics》2006,41(4-5):479-486
A key geodetic contribution to both the three Global Observing Systems and initiatives like the European Global Monitoring for Environment and Security is an accurate, long-term stable, and easily accessible reference frame as the backbone. Many emerging scientific as well as non-scientific high-accuracy applications require access to an unique, technique-independent reference frame decontaminated for short-term fluctuations due to global Earth system processes. Such a reference frame can only be maintained and made available through an observing system such as the Global Geodetic Observing System (GGOS), which is currently implemented and expected to provide sufficient information on changes in the Earth figure, its rotation and its gravity field. Based on a number of examples from monitoring of infrastructure, point positioning, maintenance of national references frames to global changes studies, likely future accuracy requirements for a global terrestrial reference frame are set up as function of time scales. Expected accuracy requirements for a large range of high-accuracy applications are less than 5 mm for diurnal and sub-diurnal time scales, 2–3 mm on monthly to seasonal time scales, better than 1 mm/year on decadal to 50 years time scales. Based on these requirements, specifications for a geodetic observing system meeting the accuracy requirements can be derived. 相似文献
2.
Terrestrial reference frame requirements within GGOS perspective 总被引：4，自引：0，他引：4
One of the main objectives of the promising and challenging IAG project GGOS (Global Geodetic Observing System) is the availability of a global and accurate Terrestrial Reference Frame for Earth Science applications, particularly Earth Rotation, Gravity Field and geophysics. With the experience gained within the activities related to the International Terrestrial Reference System (ITRS) and its realization, the International Terrestrial Reference Frame (ITRF), the combination method proved its efficiency to establish a global frame benefiting from the strengths of the various space geodetic techniques and, in the same time, underlining their biases and weaknesses. In this paper we focus on the limitation factors inherent to each individual technique and to the combination, such as the current status of the observing networks, distribution of the co-location sites and their quality and accuracy of the combined frame parameters. Results of some TRF and EOP simultaneous combinations using CATREF software will be used to illustrate the current achievement and to help drawing up future goals and improvements in the GGOS framework. Beyond these technical aspects, the overall visibility and acceptance of ITRS/ITRF as international standard for science and applications is also discussed. 相似文献
3.
《Journal of Geodynamics》2006,41(4-5):363-374
One of the main objectives of the promising and challenging IAG project GGOS (Global Geodetic Observing System) is the availability of a global and accurate Terrestrial Reference Frame for Earth Science applications, particularly Earth Rotation, Gravity Field and geophysics. With the experience gained within the activities related to the International Terrestrial Reference System (ITRS) and its realization, the International Terrestrial Reference Frame (ITRF), the combination method proved its efficiency to establish a global frame benefiting from the strengths of the various space geodetic techniques and, in the same time, underlining their biases and weaknesses. In this paper we focus on the limitation factors inherent to each individual technique and to the combination, such as the current status of the observing networks, distribution of the co-location sites and their quality and accuracy of the combined frame parameters. Results of some TRF and EOP simultaneous combinations using CATREF software will be used to illustrate the current achievement and to help drawing up future goals and improvements in the GGOS framework. Beyond these technical aspects, the overall visibility and acceptance of ITRS/ITRF as international standard for science and applications is also discussed. 相似文献
4.
The International Association of Geodesy has decided to establish an Integrated Global Geodetic Observing System (IGGOS). The objective of IGGOS is to integrate in a well-defined global terrestrial reference frame the three fundamental pillars of geodesy, which are the determination of all variations of surface geometry of our planet (land, ice and ocean surfaces), of the irregularities in Earth rotation sub-divided in changes of nutation, polar motion and spin rate, and of the spatial and temporal variations of gravity and of the geoid. This integration will have to be done with a relative precision of 1 part-per-billion and be maintained stable in space and time over decades. IGGOS will quantify on a global scale surface changes, mass anomalies, mass transport and mass exchange and exchange in angular momentum in system Earth. It will be a novel and unique contribution to Earth system and Global Change research. It is intended to make IGGOS part of the Integrated Global Observing Strategy (IGOS). 相似文献
5.
6.
Jaroslaw Bosy 《Pure and Applied Geophysics》2014,171(6):783-808
In July 2003 the International Association of Geodesy (IAG) established the Global Geodetic Observing System (GGOS). The GGOS is integrating the three basic components: geometry, the earth rotation and gravity. The backbone of this integration is the existing global ground network, based on the geodetic space techniques: very long baseline interferometry, satellite laser ranging, global navigation satellite systems and Doppler orbitography and radiopositioning integrated by satellite. These techniques have to operate as one global entity and in one global reference frame. The global reference frame in the GGOS is a realization of the International Terrestrial Reference System (ITRS). The ITRS is a world spatial reference system co-rotating with the Earth in its diurnal motion in the space. The IAG Subcommision for the European Reference Frame (EUREF) in 1991 recommended that the terrestrial reference system for Europe should be coincident with ITRS at the epoch t 0 = 1989.0 and fixed to the stable part of the Eurasian Plate. It was named the European Terrestrial Reference System 89 (ETRS89). On the 2nd of June 2008, the Head Office of Geodesy and Cartography in Poland commenced operating the ASG-EUPOS multifunctional precise satellite positioning system. The ASG-EUPOS network defines the European Terrestrial Reference System ETRS89 in Poland. A close connection between the ASG-EUPOS stations and 15 out of 18 Polish EUREF permanent network stations controls the realization of the ETRS89 on Polish territory. This paper is a review of the global ITRS, as well as a regional and a national geodetic reference systems ETRS89. 相似文献
7.
《Journal of Geodynamics》2006,41(4-5):357-362
The International Association of Geodesy has decided to establish an Integrated Global Geodetic Observing System (IGGOS). The objective of IGGOS is to integrate in a well-defined global terrestrial reference frame the three fundamental pillars of geodesy, which are the determination of all variations of surface geometry of our planet (land, ice and ocean surfaces), of the irregularities in Earth rotation sub-divided in changes of nutation, polar motion and spin rate, and of the spatial and temporal variations of gravity and of the geoid. This integration will have to be done with a relative precision of 1 part-per-billion and be maintained stable in space and time over decades. IGGOS will quantify on a global scale surface changes, mass anomalies, mass transport and mass exchange and exchange in angular momentum in system Earth. It will be a novel and unique contribution to Earth system and Global Change research. It is intended to make IGGOS part of the Integrated Global Observing Strategy (IGOS). 相似文献
8.
《Journal of Geodynamics》2006,41(4-5):414-431
Towards the end of the 19th century, geodetic observation techniques allowed it to create geodetic networks of continental size. The insight that big networks can only be set up through international collaboration led to the establishment of an international collaboration called “Central European Arc Measurement”, the predecessor of the International Association of Geodesy (IAG), in 1864. The scope of IAG activities was extended already in the 19th century to include gravity.At the same time, astrometric observations could be made with an accuracy of a few tenths of an arcsecond. The accuracy stayed roughly on this level, till the space age opened the door for milliarcsecond (mas) astrometry. Astrometric observations allowed it at the end of the 19th century to prove the existence of polar motion. The insight that polar motion is almost unpredictable led to the establishment of the International Latitude Service (ILS) in 1899.The IAG and the ILS were the tools (a) to establish and maintain the terrestrial and the celestial reference systems, including the transformation parameters between the two systems, and (b) to determine the Earth's gravity field.Satellite-geodetic techniques and astrometric radio-interferometric techniques revolutionized geodesy in the second half of the 20th century. Satellite Laser Ranging (SLR) and methods based on the interferometric exploitation of microwave signals (stemming from Quasars and/or from satellites) allow it to realize the celestial reference frame with (sub-)mas accuracy, the global terrestrial reference frame with (sub-)cm accuracy, and to monitor the transformation between the systems with a high time resolution and (sub-)mas accuracy. This development led to the replacement of the ILS through the IERS, the International Earth Rotation Service in 1989.In the pre-space era, the Earth's gravity field could “only” be established by terrestrial methods. The determination of the Earth's gravitational field was revolutionized twice in the space era, first by observing geodetic satellites with optical, Laser, and Doppler techniques, secondly by implementing a continuous tracking with spaceborne GPS receivers in connection with satellite gradiometry. The sequence of the satellite gravity missions CHAMP, GRACE, and GOCE allow it to name the first decade of the 21st century the “decade of gravity field determination”.The techniques to establish and monitor the geometric and gravimetric reference frames are about to reach a mature state and will be the prevailing geodetic tools of the following decades. It is our duty to work in the spirit of our forefathers by creating similarly stable organizations within IAG with the declared goal to produce the geometric and gravimetric reference frames (including their time evolution) with the best available techniques and to make accurate and consistent products available to wider Earth sciences community as a basis for meaningful research in global change. IGGOS, the Integrated Global Geodetic Observing System, is IAG's attempt to achieve these goals. It is based on the well-functioning and well-established network of IAG services. 相似文献
9.
The Integrated Global Geodetic Observing System (IGGOS) viewed from the perspective of history 总被引：1，自引：0，他引：1
Towards the end of the 19th century, geodetic observation techniques allowed it to create geodetic networks of continental size. The insight that big networks can only be set up through international collaboration led to the establishment of an international collaboration called “Central European Arc Measurement”, the predecessor of the International Association of Geodesy (IAG), in 1864. The scope of IAG activities was extended already in the 19th century to include gravity.At the same time, astrometric observations could be made with an accuracy of a few tenths of an arcsecond. The accuracy stayed roughly on this level, till the space age opened the door for milliarcsecond (mas) astrometry. Astrometric observations allowed it at the end of the 19th century to prove the existence of polar motion. The insight that polar motion is almost unpredictable led to the establishment of the International Latitude Service (ILS) in 1899.The IAG and the ILS were the tools (a) to establish and maintain the terrestrial and the celestial reference systems, including the transformation parameters between the two systems, and (b) to determine the Earth's gravity field.Satellite-geodetic techniques and astrometric radio-interferometric techniques revolutionized geodesy in the second half of the 20th century. Satellite Laser Ranging (SLR) and methods based on the interferometric exploitation of microwave signals (stemming from Quasars and/or from satellites) allow it to realize the celestial reference frame with (sub-)mas accuracy, the global terrestrial reference frame with (sub-)cm accuracy, and to monitor the transformation between the systems with a high time resolution and (sub-)mas accuracy. This development led to the replacement of the ILS through the IERS, the International Earth Rotation Service in 1989.In the pre-space era, the Earth's gravity field could “only” be established by terrestrial methods. The determination of the Earth's gravitational field was revolutionized twice in the space era, first by observing geodetic satellites with optical, Laser, and Doppler techniques, secondly by implementing a continuous tracking with spaceborne GPS receivers in connection with satellite gradiometry. The sequence of the satellite gravity missions CHAMP, GRACE, and GOCE allow it to name the first decade of the 21st century the “decade of gravity field determination”.The techniques to establish and monitor the geometric and gravimetric reference frames are about to reach a mature state and will be the prevailing geodetic tools of the following decades. It is our duty to work in the spirit of our forefathers by creating similarly stable organizations within IAG with the declared goal to produce the geometric and gravimetric reference frames (including their time evolution) with the best available techniques and to make accurate and consistent products available to wider Earth sciences community as a basis for meaningful research in global change. IGGOS, the Integrated Global Geodetic Observing System, is IAG's attempt to achieve these goals. It is based on the well-functioning and well-established network of IAG services. 相似文献
10.
The gravity field of the earth is a natural element of the Global Geodetic Observing System (GGOS). Gravity field quantities are like spatial geodetic observations of potential very high accuracy, with measurements, currently at part-per-billion (ppb) accuracy, but gravity field quantities are also unique as they can be globally represented by harmonic functions (long-wavelength geopotential model primarily from satellite gravity field missions), or based on point sampling (airborne and in situ absolute and superconducting gravimetry). From a GGOS global perspective, one of the main challenges is to ensure the consistency of the global and regional geopotential and geoid models, and the temporal changes of the gravity field at large spatial scales. The International Gravity Field Service, an umbrella “level-2” IAG service (incorporating the International Gravity Bureau, International Geoid Service, International Center for Earth Tides, International Center for Global Earth models, and other future new services for, e.g., digital terrain models), would be a natural key element contributing to GGOS. Major parts of the work of the services would, however, remain complementary to the GGOS contributions, which focus on the long-wavelength components of the geopotential and its temporal variations, the consistent procedures for regional data processing in a unified vertical datum and Terrestrial Reference Frame, and the ensuring validations of long-wavelength gravity field data products. 相似文献
11.
M. Ablain J. F. Legeais P. Prandi M. Marcos L. Fenoglio-Marc H. B. Dieng J. Benveniste A. Cazenave 《Surveys in Geophysics》2017,38(1):7-31
Since the beginning of the 1990s, sea level is routinely measured using high-precision satellite altimetry. Over the past ~25 years, several groups worldwide involved in processing the satellite altimetry data regularly provide updates of sea level time series at global and regional scales. Here we present an ongoing effort supported by the European Space Agency (ESA) Climate Change Initiative Programme for improving the altimetry-based sea level products. Two main objectives characterize this enterprise: (1) to make use of ESA missions (ERS-1 and 2 and Envisat) in addition to the so-called ‘reference’ missions like TOPEX/Poseidon and the Jason series in the computation of the sea level time series, and (2) to improve all processing steps in order to meet the Global Climate Observing System (GCOS) accuracy requirements defined for a set of 50 Essential Climate Variables, sea level being one of them. We show that improved geophysical corrections, dedicated processing algorithms, reduction of instrumental bias and drifts, and careful linkage between missions led to improved sea level products. Regarding the long-term trend, the new global mean sea level record accuracy now approaches the GCOS requirements (of ~0.3 mm/year). Regional trend uncertainty has been reduced by a factor of ~2, but orbital and wet tropospheric corrections errors still prevent fully reaching the GCOS accuracy requirement. Similarly at the interannual time scale, the global mean sea level still displays 2–4 mm errors that are not yet fully understood. The recent launch of new altimetry missions (Sentinel-3, Jason-3) and the inclusion of data from currently flying missions (e.g., CryoSat, SARAL/AltiKa) may provide further improvements to this important climate record. 相似文献
12.
The horizontal transport of water in Earth's surface layer, including sea level change, deglaciation, and surface runoff, is a manifestation of many geophysical processes. These processes entail ocean and atmosphere circulation and tidal attraction, global climate change, and the hydrological cycle, all having a broad range of spatiotemporal scales. The largest atmospheric mass variations occur mostly at synoptic wavelengths and at seasonal time scales. The longest wavelength component of surface mass transport, the spherical harmonic degree-1, involves the exchange of mass between the northern and southern hemispheres. These degree-1 mass loads deform the solid Earth, including its surface, and induce geocenter motion between the center-of-mass of the total Earth system (CM) and the center-of-figure (CF) of the solid Earth surface. Because geocenter motion also depends on the mechanical properties of the solid Earth, monitoring geocenter motion thus provides an additional opportunity to probe deep into Earth's interior. Most modern geodetic measurement systems rely on tracking data between ground stations and satellites that orbit around CM. Consequently, geocenter motion is intimately related to the realization of the International Terrestrial Reference Frame (ITRF) origin, and, in various ways, affects many of our measurement objectives for global change monitoring. In the last 15 years, there have been vast improvements in geophysical fluid modeling and in the global coverage, densification, and accuracy of geodetic observations. As a result of these developments, tremendous progress has been made in the study of geocenter motion over the same period. This paper reviews both the theoretical and measurement aspects of geocenter motion and its implications. 相似文献
13.
A unified global height reference system as a basis for IGGOS 总被引：1，自引：0，他引：1
The definition of a global height reference system is based on a mean sea surface, gravity field parameters, and a three-dimensional terrestrial reference frame (TRF). Tide gauge records, satellite altimetry, gravity measurements on Earth and from space, TRF coordinates, and spirit levelling have to be combined for the realization of the vertical reference frame. Observations and parameters have to be consistent with respect to the used standards, conventions and models. They have to provide globally unified reference surfaces (geoid or quasigeoid, respectively, and mean sea surface). The continental reference systems of Europe (EUREF, ECGN) and South America (SIRGAS) are considering these requirements in their strategies. They are presented here, and slightly different definitions and realizations for a globally unified height reference system are discussed. 相似文献
14.
Geodetic Measurements of Crustal Deformation in the Western Mediterranean and Europe 总被引：15，自引：0，他引：15
—Geodetic measurements of crustal deformation over large areas deforming at slow rates (<5 mm/yr over more than 1000 km), such as the Western Mediterranean and Western Europe, are still a challenge because (1) these rates are close to the current resolution of the geodetic techniques, (2) inaccuracies in the reference frame implementation may be on the same order as the tectonic velocities. We present a new velocity field for Western Europe and the Western Mediterranean derived from a rigorous combination of (1) a selection of sites from the ITRF2000 solution, (2) a subset of sites from the European Permanent GPS Network solution, (3) a solution of the French national geodetic permanent GPS network (RGP), and (4) a solution of a permanent GPS network in the western Alps (REGAL). The resulting velocity field describes horizontal crustal motion at 64 sites in Western Europe with an accuracy on the order of 1 mm/yr or better. Its analysis shows that Central Europe behaves rigidly at a 0.4 mm/yr level and can therefore be used to define a stable Europe reference frame. In that reference frame, we find that most of Europe, including areas west of the Rhine graben, the Iberian peninsula, the Ligurian basin and the Corsica-Sardinian block behaves rigidly at a 0.5 mm/yr level. In a second step, we map recently published geodetic results in the reference frame previously defined. Geodetic data confirm a counterclockwise rotation of the Adriatic microplate with respect to stable Europe, that appears to control the strain pattern along its boundaries. Active deformation in the Alps, Apennines, and Dinarides is probably driven by the independent motion of the Adriatic plate rather than by the Africa-Eurasia convergence. The analysis of a global GPS solution and recently published new estimates for the African plate kinematics indicate that the Africa-Eurasia plate motion may be significantly different from the NUVEL1A values. In particular, geodetic solutions show that the convergence rate between Africa and stable Europe may be 30–60% slower than the NUVEL1A prediction and rotated 10–30° counterclockwise in the Mediterranean. 相似文献
15.
Matt A. King Zuheir Altamimi Johannes Boehm Machiel Bos Rolf Dach Pedro Elosegui François Fund Manuel Hernández-Pajares David Lavallee Paulo Jorge Mendes Cerveira Nigel Penna Riccardo E. M. Riva Peter Steigenberger Tonie van Dam Luca Vittuari Simon Williams Pascal Willis 《Surveys in Geophysics》2010,31(5):465-507
The provision of accurate models of Glacial Isostatic Adjustment (GIA) is presently a priority need in climate studies, largely due to the potential of the Gravity Recovery and Climate Experiment (GRACE) data to be used to determine accurate and continent-wide assessments of ice mass change and hydrology. However, modelled GIA is uncertain due to insufficient constraints on our knowledge of past glacial changes and to large simplifications in the underlying Earth models. Consequently, we show differences between models that exceed several mm/year in terms of surface displacement for the two major ice sheets: Greenland and Antarctica. Geodetic measurements of surface displacement offer the potential for new constraints to be made on GIA models, especially when they are used to improve structural features of the Earth’s interior as to allow for a more realistic reconstruction of the glaciation history. We present the distribution of presently available campaign and continuous geodetic measurements in Greenland and Antarctica and summarise surface velocities published to date, showing substantial disagreement between techniques and GIA models alike. We review the current state-of-the-art in ground-based geodesy (GPS, VLBI, DORIS, SLR) in determining accurate and precise surface velocities. In particular, we focus on known areas of need in GPS observation level models and the terrestrial reference frame in order to advance geodetic observation precision/accuracy toward 0.1 mm/year and therefore further constrain models of GIA and subsequent present-day ice mass change estimates. 相似文献
16.
《Journal of Geodynamics》2006,41(4-5):436-449
In the interest of improving the performance and efficiency of space geodesy a diverse group in the US, in collaboration with IGGOS, has begun to establish a unified National Geodetic Observatory (NGO). To launch this effort an international team will conduct a multi-year program of research into the technical issues of integrating SLR, VLBI, and GPS geodesy to produce a unified set of global geodetic products. The goal is to improve measurement accuracy by up to an order of magnitude while lowering the cost to current sponsors. A secondary goal is to expand and diversify international sponsorship of space geodesy. Principal benefits will be to open new vistas of research in geodynamics and surface change while freeing scarce NASA funds for scientific studies. NGO will proceed in partnership with, and under the auspices of, the International Association of Geodesy (IAG) as an element of the Integrated Global Geodetic Observation System project. The collaboration will be conducted within, and will make full use of, the IAG's existing international services: the IGS, IVS, ILRS, and IERS. Seed funding for organizational activities and technical analysis will come from NASA's Solid Earth and Natural Hazards Program. Additional funds to develop an integrated geodetic data system known as Inter-service Data Integration for Geodetic Operations (INDIGO), will come from a separate NASA program in Earth science information technology. INDIGO will offer ready access to the full variety of NASA's space geodetic data and will extend the GPS Seamless Archive (GSAC) philosophy to all space geodetic data types. 相似文献
17.
18.
《Journal of Geodynamics》2006,41(4-5):494-501
We have processed all available DORIS data from all available satellites, except Jason-1 over the past 10 years (from January 1993 to April 2003). Weekly solutions have been produced for stations positions coordinates, geocenter motion and scale factor stability. We present here accuracy presently achievable for all types of potential geodetic products. Typically weekly stations positions can be derived with a repeatability of 1.0–1.5 cm using data from 5 satellites simultaneously, showing the significant improvement in precision that has been gained recently using the additional new DORIS satellites. As an example, we show how such new results can detect displacement from large magnitude earthquakes, such as the 2003 Denali fault earthquake in Alaska. Displacements of −5 cm in latitude and +2 cm in longitude were easily detected using the DORIS data and are confirmed by recent GPS determination. The terrestrial reference frame was also well be monitored with DORIS during this 10-year period. Other geodetic products, such as tropospheric corrections for atmospheric studies are also analyzed. Finally, we discuss here the possible advantages and weaknesses of the DORIS system as additional geodetic tool, in conjunction with the already existing GPS, VLBI and SLR services, to participate in an Global Geodetic Observing System (GGOS). 相似文献
19.
Yu. O. Kuzmin 《Izvestiya Physics of the Solid Earth》2017,53(6):825-839
The comparative analysis of the Earth’s surface deformations measured by ground-based and satellite geodetic methods on the regional and zonal measurement scales is carried out. The displacement velocities and strain rates are compared in the active regions such as Turkmenian–Iranian zone of interaction of the Arabian and Eurasian lithospheric plates and the Kamchatka segment of the subduction of the Pacific Plate beneath the Okotsk Plate. The comparison yields a paradoxical result. With the qualitatively identical kinematics of the motion, the quantitative characteristics of the displacement velocities and rates of strain revealed by the observations using the global navigational satellite system (GNSS) are by 1–2 orders of magnitude higher than those estimated by the more accurate methods of ground-based geodesy. For resolving the revealed paradoxes, it is required to set up special studies on the joint analysis of ground-based and satellite geodetic data from the combined observation sites. 相似文献
20.
《Journal of Geodynamics》2010,49(3-5):299-304
The Global Geodynamics Project (GGP) started on July 1, 1997 and is now in its 11th year of operation. It has a relatively small number of stations (24), compared to seismic (GSN) or geodetic (GPS) networks, but it is the only database that is accumulating relative gravity measurements worldwide. As any scientific organization matures, there is a change in the culture of the project and the people involved. To remain viable, it is necessary not only to maintain the original goals, but also to incorporate new ideas and applications on the science involved. The main challenges within GGP are to ensure: (a) that the instruments are properly calibrated, (b) that data is being recorded with the highest accuracy, and with appropriate hydrological instrumentation, and (c) that the flow of data from all recording stations to the ICET database continues as agreed in within the GGP framework. These practical matters are the basis for providing high quality recordings that will extend the usefulness of the network into the future to meet new challenges in geosciences. Several new stations have been brought into operation in the past few years, but the data availability from some of these stations still leaves room for improvement. Nevertheless, the core group of stations established more than 10 years ago has been able to maintain the high standards of the original concept, and much research has been published using network data in areas as diverse as hydrology, polar motion, and Earth's normal modes. GGP will also participate in some of the scientific tasks of the Global Geodetic Observing System program, at least initially by providing relative gravity measurements for collocation with other high precision geodetic measurements. 相似文献