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1.
《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   

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.
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   

4.
5.
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   

6.
《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   

7.
GPS-derived height changes in diurnal and sub-diurnal timescales   总被引:1,自引:0,他引:1  
This paper describes the research concerning precise short-time GPS solutions conducted in the Centre of Applied Geomatics, Military University of Technology, Warsaw, Poland. The data from ASG-EUPOS (Polish Active Geodetic Network) was processed using Bernese 5.0 software and EPN (EUREF Permanent Network) standards and models. In this study, the adapted 3-hour observation window is shifted every hour for obtaining hourly geocentric coordinates in ITRF2005 reference frame. The adjusted network consisted of over 130 stations from Poland and the neighbouring countries, the period covered observations collected from June 2008 through June 2010. These two years of observations allowed for examining short-period oscillations which were found to be closely related to the tidal (dynamic) frequencies. The analysis of the residua from the IERS2003 tidal model was performed using the least squares method with the Eterna software. It confirmed the existence of significant (several millimetres) oscillations in the frequencies corresponding to S1, K1 and K2. The paper describes the idea of data processing and analysis, presents the results of vertical (the Up component) oscillations in main tidal frequency bands, and also includes discussion of possible explanation of the existence of short-period oscillations in the GPS precise solutions and the possibility of propagation of short-period oscillations into long-period spurious changes in the daily (standard) GPS solutions.  相似文献   

8.
In the past 30 years the Satellite Laser Ranging(SLR) technique has improved to a large extent, currently achieving a ranging precision down toa few millimeters. Moreover the growth in the size of the international network of SLR stations and therapidly growing constellation of geodetic target satellites make the SLR a well established technique for solidEarth studies and for the related Earth subsystem sciences. The long SLR observation history has become a veryimportant source of data for global and local changes detection and monitoring in many different fields.Tectonic plate motion, crustal deformation, post-glacial rebound and subsidence, Earth rotation, and polarmotion, time variations of the Earth's gravitational field, ocean tides modeling, center of mass of the totalEarth system monitoring, International Terrestrial Reference System (ITRS) maintenance are only themain applications in which the SLR technique plays a significant role. Plate boundary zones in whichdeformation is diffuse are in general geographical areas associated with high seismic and volcanic activity.A principal key to understand the geophysics of a plate boundary process is the detailed knowledge of the3-D kinematics. This work will focus on the relevant results of the Eurasian SLR subnetwork in termsof technological evolution and crustal deformation. A general overview of the Eurasian SLR stationperformance will be presented with particular reference to the state-of-the-art SLR observatory MLRO (Matera LaserRanging Observatory). The current tectonic deformations (velocity and strain-rate field) detectedby the Eurasian network and by the former WEGENER/MEDLAS campaigns will also be discussed.  相似文献   

9.
—GPS (Global Positioning System) observations started to be carried out in the Azores region under the scope of the TANGO (TransAtlantic Network for Geodesy and Oceanography) project in 1988. The measurements carried out between 1993 and 2000 (five campaigns) on nine GPS sites (one per island) were reprocessed using two state–of–the-art software packages. Different methodologies were applied to compute each campaign solution and the derived velocity field. The velocity fields, including the motions of two permanent stations, recently installed in the Azores, were computed within the most recent geodetic reference frame, ITRF2000 (International Terrestrial Reference Frame, solution 2000). They are compared with the motions of the stable rigid tectonic plates using as reference DEOS2k, a global tectonic model developed using geodetic data. The relative motions between the Western and Central groups of islands yield to evaluate the opening rate of the Mid-Atlantic Ridge (boundary between the North American plate and the Eurasian and African plates). Concerning the boundary between the Eurasian and African plates, the motion of the TANGO sites in the Central and Eastern groups clearly identifies the transition pattern between those two plates. Two of the sites are considered to be located in the stable part of these plates, whereas the remaining five are within the deformation region of the Eurasia-Africa boundary. The conclusions are analyzed in view of the different deformation models, derived from geodynamic or geophysical data that have been proposed for the region.  相似文献   

10.
In 1988 the interdisciplinary role of space geodesy has been discussed by a prominent group of leaders in the fields of geodesy and geophysics at an international workshop in Erice (Mueller and Zerbini, 1989). The workshop may be viewed as the starting point of a new era of geodesy as a discipline of Earth sciences. Since then enormous progress has been made in geodesy in terms of satellite and sensor systems, observation techniques, data processing, modelling and interpretation. The establishment of a Global Geodetic Observing System (GGOS) which is currently underway is a milestone in this respect. Wegener served as an important role model for the definition of GGOS. In turn, Wegener will benefit from becoming a regional entity of GGOS.What are the great challenges of the realisation of a 10?9 global integrated observing system? Geodesy is potentially able to provide – in the narrow sense of the words – “metric and weight” to global studies of geo-processes. It certainly can meet this expectation if a number of fundamental challenges, related to issues such as the international embedding of GGOS, the realisation of further satellite missions and some open scientific questions can be solved. Geodesy is measurement driven. This is an important asset when trying to study the Earth as a system. However its guideline must be: “What are the right and most important observables to deal with the open scientific questions?”.  相似文献   

11.
The International Laser Ranging Service (ILRS) was established in September 1998 as a service within the IAG to support programs in geodetic, geophysical, and lunar research activities and to provide data products to the International Earth Rotation Service (IERS) in support of its prime objectives. Now in operation for 5 years, the ILRS develops: (1) the standards and specifications necessary for product consistency and (2) the priorities and tracking strategies required to maximize network efficiency. The service collects, merges, analyzes, archives and distributes satellite and lunar laser ranging data to satisfy a variety of scientific, engineering, and operational needs and encourages the application of new technologies to enhance the quality, quantity, and cost effectiveness of its data products. The ILRS works with: (1) the global network to improve station performance; (2) new satellite missions in the design and building of retroreflector targets to maximize data quality and quantity and (3) science programs to optimize scientific data yield. The ILRS Central Bureau maintains a comprehensive web site as the primary vehicle for the distribution of information within the ILRS community. The site, which can be accessed at: http://ilrs.gsfc.nasa.gov is also available at mirrored sites at the Communications Research Laboratory (CRL) in Tokyo and the European Data Center (EDC) in Munich.During the last 2 years, the ILRS has addressed very important challenges: (1) data from the field stations are now submitted hourly and made available immediately through the data centers for access by the user community; (2) tracking on low satellites has been significantly improved through the sub-daily issue of predictions, drag functions, and the real-time exchange of time biases; (3) analysis products are now submitted in SINEX format for compatibility with the other space geodesy techniques; (4) the Analysis Working Group is heavily engaged in Pilot Projects as it works toward an ILRS “standard” global solution and (5) SLR has significantly increased its participation in the International Terrestrial Reference Frame (ITRF) activity, which is important to the success of IGGOS.  相似文献   

12.
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   

13.
邹蓉  孙付平  王啸  黎争 《中国地震》2020,36(4):684-692
地球参考框架是国家重要的空间基础设施,是地球上人类所有活动的空间参考基准。本文首先阐述了国际地球参考框架(International Terrestrial Reference Frame,ITRF)的发展现状,重点评述了ITRF的建立与维持,针对ITRF的发展现状提出了存在的问题;其次,以ITRF与2000国家大地坐标系(China Geodetic Coordinate System 2000,CGCS2000)的关系及现状为切入点,探讨了我国建立北斗坐标系的必要性,介绍了建立北斗坐标系的基本思路以及初始实现;最后,对地球参考框架的未来发展进行了展望。  相似文献   

14.
《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   

15.
卫星激光测距(SLR)技术作为卫星精密定轨手段和轨道检核重要方法,激光反射器已经成为重力卫星和测高卫星等低轨卫星的基本载荷.经典的SLR台站坐标是使用动力学方法计算的,本文根据多颗低轨卫星(LEO)多历元的激光观测数据,采用几何方法开展地面SLR测站坐标计算.通过组建低轨卫星群实现对全球激光站的动态观测,为了合理配置不同低轨卫星间观测值权重,削弱低轨卫星群可能存在的系统性偏差,提出采用方差分量估计组合的最小二乘法进行解算.实测结果显示,解算出SLR台站坐标框架解与SLRF2014差异平均值在25.1 mm,外符合精度达到1~2 cm.该方法避免了复杂动力学模型,SLR台站坐标的几何计算方法既可以作为激光测站框架解算手段之一,同时将LEO卫星群作为空间并址站实现不同技术地球参考框架间的融合.  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.
《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   

18.
The paper concerns investigation of the credibility of tectonic interpretation of GNSS strain rates. The analysis was focused on stable regions, where the crustal deformations are small and the reliability of GNSS velocities is questionable. We are showing how the unreliable motion of stations affects calculated strains around them. We expressed distribution of local principal strains by a sinusoidal function and used them to investigate the significance of strain distortion. Then we used this method to investigate real motions of GNSS stations. As a test object we used Polish GNSS stations belonging to the ASG-EUPOS network. Station velocities were estimated on the basis of the 4.5 years of observations. The results let us identify stations that disturb the obtained local GNSS strain rate field. After verification and exclusion of some stations, the new GNSS strains show a much greater internal compatibility and also better fit to the directions of lithosphere stresses.  相似文献   

19.
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   

20.
The paper presents the results of testing the various methods of permanent stations’ velocity residua interpolation in a regular grid, which constitutes a continuous model of the velocity field in the territory of Poland. Three packages of software were used in the research from the point of view of interpolation: GMT (The Generic Mapping Tools), Surfer and ArcGIS. The following methods were tested in the softwares: the Nearest Neighbor, Triangulation (TIN), Spline Interpolation, Surface, Inverse Distance to a Power, Minimum Curvature and Kriging. The presented research used the absolute velocities’ values expressed in the ITRF2005 reference frame and the intraplate velocities related to the NUVEL model of over 300 permanent reference stations of the EPN and ASG-EUPOS networks covering the area of Europe. Interpolation for the area of Poland was done using data from the whole area of Europe to make the results at the borders of the interpolation area reliable. As a result of this research, an optimum method of such data interpolation was developed. All the mentioned methods were tested for being local or global, for the possibility to compute errors of the interpolated values, for explicitness and fidelity of the interpolation functions or the smoothing mode. In the authors’ opinion, the best data interpolation method is Kriging with the linear semivariogram model run in the Surfer programme because it allows for the computation of errors in the interpolated values and it is a global method (it distorts the results in the least way). Alternately, it is acceptable to use the Minimum Curvature method. Empirical analysis of the interpolation results obtained by means of the two methods showed that the results are identical. The tests were conducted using the intraplate velocities of the European sites. Statistics in the form of computing the minimum, maximum and mean values of the interpolated North and East components of the velocity residuum were prepared for all the tested methods, and each of the resulting continuous velocity fields was visualized by means of the GMT programme. The interpolated components of the velocities and their residua are presented in the form of tables and bar diagrams.  相似文献   

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