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1.
CONT08 was a 15 days campaign of continuous Very Long Baseline Interferometry (VLBI) sessions during the second half of August 2008 carried out by the International VLBI Service for Geodesy and Astrometry (IVS). In this study, VLBI estimates of troposphere zenith total delays (ZTD) and gradients during CONT08 were compared with those derived from observations with the Global Positioning System (GPS), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and water vapor radiometers (WVR) co-located with the VLBI radio telescopes. Similar geophysical models were used for the analysis of the space geodetic data, whereas the parameterization for the least-squares adjustment of the space geodetic techniques was optimized for each technique. In addition to space geodetic techniques and WVR, ZTD and gradients from numerical weather models (NWM) were used from the European Centre for Medium-Range Weather Forecasts (ECMWF) (all sites), the Japan Meteorological Agency (JMA) and Cloud Resolving Storm Simulator (CReSS) (Tsukuba), and the High Resolution Limited Area Model (HIRLAM) (European sites). Biases, standard deviations, and correlation coefficients were computed between the troposphere estimates of the various techniques for all eleven CONT08 co-located sites. ZTD from space geodetic techniques generally agree at the sub-centimetre level during CONT08, and??as expected??the best agreement is found for intra-technique comparisons: between the Vienna VLBI Software and the combined IVS solutions as well as between the Center for Orbit Determination (CODE) solution and an IGS PPP time series; both intra-technique comparisons are with standard deviations of about 3?C6?mm. The best inter space geodetic technique agreement of ZTD during CONT08 is found between the combined IVS and the IGS solutions with a mean standard deviation of about 6?mm over all sites, whereas the agreement with numerical weather models is between 6 and 20?mm. The standard deviations are generally larger at low latitude sites because of higher humidity, and the latter is also the reason why the standard deviations are larger at northern hemisphere stations during CONT08 in comparison to CONT02 which was observed in October 2002. The assessment of the troposphere gradients from the different techniques is not as clear because of different time intervals, different estimation properties, or different observables. However, the best inter-technique agreement is found between the IVS combined gradients and the GPS solutions with standard deviations between 0.2 and 0.7?mm.  相似文献   

2.
Precise transformation between the celestial reference frames (CRF) and terrestrial reference frames (TRF) is needed for many purposes in Earth and space sciences. According to the Global Geodetic Observing System (GGOS) recommendations, the accuracy of positions and stability of reference frames should reach 1 mm and 0.1 mm year\(^{-1}\), and thus, the Earth Orientation Parameters (EOP) should be estimated with similar accuracy. Different realizations of TRFs, based on the combination of solutions from four different space geodetic techniques, and CRFs, based on a single technique only (VLBI, Very Long Baseline Interferometry), might cause a slow degradation of the consistency among EOP, CRFs, and TRFs (e.g., because of differences in geometry, orientation and scale) and a misalignment of the current conventional EOP series, IERS 08 C04. We empirically assess the consistency among the conventional reference frames and EOP by analyzing the record of VLBI sessions since 1990 with varied settings to reflect the impact of changing frames or other processing strategies on the EOP estimates. Our tests show that the EOP estimates are insensitive to CRF changes, but sensitive to TRF variations and unmodeled geophysical signals at the GGOS level. The differences between the conventional IERS 08 C04 and other EOP series computed with distinct TRF settings exhibit biases and even non-negligible trends in the cases where no differential rotations should appear, e.g., a drift of about 20 \(\upmu \)as year\(^{-1 }\)in \(y_{\mathrm{pol }}\) when the VLBI-only frame VTRF2008 is used. Likewise, different strategies on station position modeling originate scatters larger than 150 \(\upmu \)as in the terrestrial pole coordinates.  相似文献   

3.
ITRF2008: an improved solution of the international terrestrial reference frame   总被引：53，自引：38，他引：15  
ITRF2008 is a refined version of the International Terrestrial Reference Frame based on reprocessed solutions of the four space geodetic techniques: VLBI, SLR, GPS and DORIS, spanning 29, 26, 12.5 and 16?years of observations, respectively. The input data used in its elaboration are time series (weekly from satellite techniques and 24-h session-wise from VLBI) of station positions and daily Earth Orientation Parameters (EOPs). The ITRF2008 origin is defined in such a way that it has zero translations and translation rates with respect to the mean Earth center of mass, averaged by the SLR time series. Its scale is defined by nullifying the scale factor and its rate with respect to the mean of VLBI and SLR long-term solutions as obtained by stacking their respective time series. The scale agreement between these two technique solutions is estimated to be 1.05 ± 0.13 ppb at epoch 2005.0 and 0.049 ± 0.010?ppb/yr. The ITRF2008 orientation (at epoch 2005.0) and its rate are aligned to the ITRF2005 using 179 stations of high geodetic quality. An estimate of the origin components from ITRF2008 to ITRF2005 (both origins are defined by SLR) indicates differences at epoch 2005.0, namely: ?0.5, ?0.9 and ?4.7?mm along X, Y and Z-axis, respectively. The translation rate differences between the two frames are zero for Y and Z, while we observe an X-translation rate of 0.3?mm/yr. The estimated formal errors of these parameters are 0.2?mm and 0.2?mm/yr, respectively. The high level of origin agreement between ITRF2008 and ITRF2005 is an indication of an imprecise ITRF2000 origin that exhibits a Z-translation drift of 1.8?mm/yr with respect to ITRF2005. An evaluation of the ITRF2008 origin accuracy based on the level of its agreement with ITRF2005 is believed to be at the level of 1?cm over the time-span of the SLR observations. Considering the level of scale consistency between VLBI and SLR, the ITRF2008 scale accuracy is evaluated to be at the level of 1.2?ppb (8?mm at the equator) over the common time-span of the observations of both techniques. Although the performance of the ITRF2008 is demonstrated to be higher than ITRF2005, future ITRF improvement resides in improving the consistency between local ties in co-location sites and space geodesy estimates.  相似文献   

4.
We present comparisons of 10-year-long time series of the atmospheric zenith wet delay (ZWD), estimated using the global positioning system (GPS), geodetic very long baseline interferometry (VLBI), a water vapour radiometer (WVR), radiosonde (RS) observations, and the reanalysis product of the European Centre for Medium-Range Weather Forecasts (ECMWF). To compare the data sets with each other, a Gaussian filter is applied. The results from 10 GPS–RS comparisons using sites in Sweden and Finland show that the full width at half maximum at which the standard deviation (SD) is a minimum increases with the distance between each pair. Comparisons between three co-located techniques (GPS, VLBI, and WVR) result in mean values of the ZWD differences at a level of a few millimetres and SD of less than 7?mm. The best agreement is seen in the GPS–VLBI comparison with a mean difference of ?3.4?mm and an SD of 5.1?mm over the 10-year period. With respect to the ZWD derived from other techniques, a positive bias of up to ~7?mm is obtained for the ECMWF reanalysis product. Performing the comparisons on a monthly basis, we find that the SD including RS or ECMWF varies with the season, between 3 and 15?mm. The monthly SD between GPS and WVR does not have a seasonal signature and varies from 3 to 7?mm.  相似文献   

5.
Within the International VLBI Service for Geodesy and Astrometry (IVS) Monte Carlo simulations have been carried out to design the next generation VLBI system (“VLBI2010”). Simulated VLBI observables were generated taking into account the three most important stochastic error sources in VLBI, i.e. wet troposphere delay, station clock, and measurement error. Based on realistic physical properties of the troposphere and clocks we ran simulations to investigate the influence of the troposphere on VLBI analyses, and to gain information about the role of clock performance and measurement errors of the receiving system in the process of reaching VLBI2010’s goal of mm position accuracy on a global scale. Our simulations confirm that the wet troposphere delay is the most important of these three error sources. We did not observe significant improvement of geodetic parameters if the clocks were simulated with an Allan standard deviation better than 1 × 10−14 at 50 min and found the impact of measurement errors to be relatively small compared with the impact of the troposphere. Along with simulations to test different network sizes, scheduling strategies, and antenna slew rates these studies were used as a basis for the definition and specification of VLBI2010 antennas and recording system and might also be an example for other space geodetic techniques.  相似文献   

6.
卫星重力场探测及空间和地面大地测量联合观测   总被引：1，自引：0，他引：1  
国际大地测量与地球物理联合会(IUGG)第廿四届大会于2007年7月上旬在意大利举行,本文结合这次大会对重力卫星CHAMP、GRACE和GOCE的目前概况作简要介绍,对它们在探测地球重力场方面的进展进行了评述。对国际大地测量协会(IAG)提出的"全球大地测量观测系统GGOS"和"整合空间大地测量技术作为全球大地测量和地球物理观测系统的基础GGOS-D"项目中"共点"测量的重要性进行了评述,并对这类共点测量成果解算应注意事项进行了介绍。最后将国际大地测量与地球物理联合会(IUGG)主席和秘书长在第廿四届大会开幕式上的报告和答记者问摘编后作为本文附录供参考。  相似文献   

7.
王鹏  吕志平  张西光 《四川测绘》2010,33(1):3-6,21
详细探讨了相似变换在地球参考框架的基准定义实施中的相关模型及方法。利用四种空间大地测量技术（GPS、SLR、DORIS、VLBI）在2000．0历元的站坐标组文件,对ITRF2005的内符精度进行了实验评价。  相似文献   

8.
Multi-technique space geodetic analysis software has been developed which allows to combine data on the observation level. In addition to local tie information, site-wise common parameters, i.e., troposphere and clocks, can be estimated with this software. Thus, it will be discussed how common parameters have to be estimated and where biases/offsets need to be taken into account. To test such a novel concept, Global Positioning System (GPS) and Very Long Baseline Interferometry (VLBI) data from the CONT11 campaign are being utilized. Since the VLBI baselines of this campaign extend over several thousands of kilometers, GPS data are processed in precise-point positioning mode and satellite orbits and clocks are kept fixed to the IGS final products. From the obtained results, it can be shown that the combination of space geodetic data on the observation level leads to a consistent improvement of station position repeatability as well as nuisance parameters like troposphere estimates. Furthermore, estimation of common parameters (troposphere or clocks) at co-located sites helps to improve the solution further and derive an utmost physically consistent model of the concerned parameters.  相似文献   

9.
The CONT02 campaign is of great interest for studies combining very long baseline interferometry (VLBI) with other space-geodetic techniques, because of the continuously available VLBI observations over 2 weeks in October 2002 from a homogeneous network. Especially, the combination with the Global Positioning System (GPS) offers a broad spectrum of common parameters. We combined station coordinates, Earth orientation parameters (EOPs) and troposphere parameters consistently in one solution using technique- specific datum-free normal equation systems. In this paper, we focus on the analyses concerning the EOPs, whereas the comparison and combination of the troposphere parameters and station coordinates are covered in a companion paper in Journal of Geodesy. In order to demonstrate the potential of the VLBI and GPS space-geodetic techniques, we chose a sub-daily resolution for polar motion (PM) and universal time (UT). A consequence of this solution set-up is the presence of a one-to-one correlation between the nutation angles and a retrograde diurnal signal in PM. The Bernese GPS Software used for the combination provides a constraining approach to handle this singularity. Simulation studies involving both nutation offsets and rates helped to get a deeper understanding of this singularity. With a rigorous combination of UT1–UTC and length of day (LOD) from VLBI and GPS, we showed that such a combination works very well and does not suffer from the systematic effects present in the GPS-derived LOD values. By means of wavelet analyses and the formal errors of the estimates, we explain this important result. The same holds for the combination of nutation offsets and rates. The local geodetic ties between GPS and VLBI antennas play an essential role within the inter-technique combination. Several studies already revealed non-negligible discrepancies between the terrestrial measurements and the space-geodetic solutions. We demonstrate to what extent these discrepancies propagate into the combined EOP solution.  相似文献   

10.
Results of the VLBI experiments conducted with Syowa Station, Antarctica   总被引：1，自引：0，他引：1  
The first successful geodetic Very Long Baseline Interferometry (VLBI) observations to Antarctica were made on baselines from Syowa Station (Antarctica) to Tidbinbilla (Australia) and to Kashima (Japan) in January 1990. Regular geodetic experiments started in 1998 with the installation of a permanent VLBI terminal at Syowa Station. These observations are conducted at the standard geodetic VLBI frequencies of 2.3 and 8.4 GHz, S- and X-Bands. In the first year, the 11-m multipurpose antenna at Syowa Station observed together with the 26-m radio telescope of the University of Tasmania in Australia and the 26-m radio telescope of the Hartebeesthoek Radio Astronomy Observatory in South Africa. From 1999, the experiments were expanded to also include the O’Higgins Station in Antarctica, Fortaleza in Brazil and Kokee on Hawaii. From 1999 until the end of 2003, 25 observing sessions have been reduced and analyzed using the CALC/SOLVE geodetic VLBI data reduction package. The results show that the horizontal baseline of Syowa-Hobart is increasing at the rate of 57.0±1.9 mm/year. The baseline Syowa-Hartebeesthoek is also increasing, but at the lower rate of 9.8±1.9 mm/year. The VLBI result of 2.0±3.1 mm/year and the GPS result of −1.9±0.7 mm/year for the Syowa-O’Higgins horizontal baseline support the hypothesis of one rigid Antarctic plate without intra-plate deformation, which is consistent with the NNR-NUVEL-1A global plate motion model. The location of the Euler pole of the Antarctic plate by VLBI is estimated as 59.7°S and 62.6°E with a rotation rate of 0.190 deg/Myr, while that by GPS in our study is estimated as 60.6°S and 42.2°E with a rotation rate of 0.221 deg/Myr. These pole positions are slightly different to that implied by the NNR-NUVEL-1A model of 63.0°S and 64.2°E with a rotation rate of 0.238 deg/Myr. VLBI observations over a longer time span may resolve small discrepancy of current plate motion from the NNR-NUVEL-1A model. The consistency of the VLBI coordinates with the GPS coordinates at Syowa Station, after correction for the local tie vector components between the two reference markers, is also discussed.  相似文献   

11.
The 2008 DGFI realization of the ITRS: DTRF2008   总被引：11，自引：11，他引：0  
A new realization of the International Terrestrial System was computed at the ITRS Combination Centre at DGFI as a contribution to ITRF2008. The solution is labelled DTRF2008. In the same way as in the DGFI computation for ITRF2005 it is based on either normal equation systems or estimated parameters derived from VLBI, SLR, GPS and DORIS observations by weekly or session-wise processing. The parameter space of the ITRS realization comprises station positions and velocities and daily resolved Earth Orientation Parameters (EOP), whereby for the first time also nutation parameters are included. The advantage of starting from time series of input data is that the temporal behaviour of geophysical parameters can be investigated to decide whether the parameters can contribute to the datum realization of the ITRF. In the same way, a standardized analysis of station position time series can be performed to detect and remove discontinuities. The advantage of including EOP in the ITRS realization is twofold: (1) the combination of the coordinates of the terrestrial pole—estimated from all contributing techniques—links the technique networks in two components of the orientation, leading to an improvement of consistency of the Terrestrial Reference Frame (TRF) and (2) in their capacity as parameters common to all techniques, the terrestrial pole coordinates enhance the selection of local ties as they provide a measure for the consistency of the combined frame. The computation strategy of DGFI is based on the combination of normal equation systems while at the ITRS Combination Centre at IGN solutions are combined. The two independent ITRS realizations provide the possibility to assess the accuracy of ITRF by comparison of the two frames. The accuracy evaluation was done separately for the datum parameters (origin, orientation and scale) and the network geometry. The accuracy of the datum parameters, assessed from the comparison of DTRF2008 and ITRF2008, is between 2–5?mm and 0.1–0.8?mm/year depending on the technique. The network geometry (station positions and velocities) agrees within 3.2?mm and 1.0?mm/year. A comparison of DTRF2008 and ITRF2005 provides similar results for the datum parameters, but there are larger differences for the network geometry. The internal accuracy of DTRF2008—that means the level of conservation of datum information and network geometry within the combination—was derived from comparisons with the technique-only multi-year solutions. From this an internal accuracy of 0.32?mm for the VLBI up to 3.3?mm for the DORIS part of the network is found. The internal accuracy of velocities ranges from 0.05?mm/year for VLBI to 0.83?mm/year for DORIS. The internal consistency of DTRF2008 for orientation can be derived from the analysis of the terrestrial pole coordinates. It is estimated at 1.5–2.5?mm for the GPS, VLBI and SLR parts of the network. The consistency of these three and the DORIS network part is within 6.5?mm.  相似文献   

12.
Quality assessment of GPS reprocessed terrestrial reference frame   总被引：5，自引：1，他引：4  
The International GNSS Service (IGS) contributes to the construction of the International Terrestrial Reference Frame (ITRF) by submitting time series of station positions and Earth Rotation Parameters (ERP). For the first time, its submission to the ITRF2008 construction is based on a combination of entirely reprocessed GPS solutions delivered by 11 Analysis Centers (ACs). We analyze the IGS submission and four of the individual AC contributions in terms of the GNSS frame origin and scale, station position repeatability and time series seasonal variations. We show here that the GPS Terrestrial Reference Frame (TRF) origin is consistent with Satellite laser Ranging (SLR) at the centimeter level with a drift lower than 1 mm/year. Although the scale drift compared to Very Long baseline Interferometry (VLBI) and SLR mean scale is smaller than 0.4 mm/year, we think that it would be premature to use that information in the ITRF scale definition due to its strong dependence on the GPS satellite and ground antenna phase center variations. The new position time series also show a better repeatability compared to past IGS combined products and their annual variations are shown to be more consistent with loading models. The comparison of GPS station positions and velocities to those of VLBI via local ties in co-located sites demonstrates that the IGS reprocessed solution submitted to the ITRF2008 is more reliable and precise than any of the past submissions. However, we show that some of the remaining inconsistencies between GPS and VLBI positioning may be caused by uncalibrated GNSS radomes.  相似文献   

13.
We perform extensive simulations in order to assess the accuracy with which the position of a radio transmitter on the surface of the Moon can be determined by geodetic VLBI. We study how the quality and quantity of geodetic VLBI observations influence these position estimates and investigate how observations of such near-field objects affect classical geodetic parameters like VLBI station coordinates and Earth rotation parameters. Our studies are based on today’s global geodetic VLBI schedules as well as on those designed for the next-generation geodetic VLBI system. We use Monte Carlo simulations including realistic stochastic models of troposphere, station clocks, and observational noise. Our results indicate that it is possible to position a radio transmitter on the Moon using today’s geodetic VLBI with a two-dimensional horizontal accuracy of better than one meter. Moreover, we show that the next-generation geodetic VLBI has the potential to improve the two-dimensional accuracy to better than 5 cm. Thus, our results lay the base for novel observing concepts to improve both lunar research and geodetic VLBI.  相似文献   

14.
The Celestial Reference System (CRS) is currently realized only by Very Long Baseline Interferometry (VLBI) because it is the space geodetic technique that enables observations in that frame. In contrast, the Terrestrial Reference System (TRS) is realized by means of the combination of four space geodetic techniques: Global Navigation Satellite System (GNSS), VLBI, Satellite Laser Ranging (SLR), and Doppler Orbitography and Radiopositioning Integrated by Satellite. The Earth orientation parameters (EOP) are the link between the two types of systems, CRS and TRS. The EOP series of the International Earth Rotation and Reference Systems Service were combined of specifically selected series from various analysis centers. Other EOP series were generated by a simultaneous estimation together with the TRF while the CRF was fixed. Those computation approaches entail inherent inconsistencies between TRF, EOP, and CRF, also because the input data sets are different. A combined normal equation (NEQ) system, which consists of all the parameters, i.e., TRF, EOP, and CRF, would overcome such an inconsistency. In this paper, we simultaneously estimate TRF, EOP, and CRF from an inter-technique combined NEQ using the latest GNSS, VLBI, and SLR data (2005–2015). The results show that the selection of local ties is most critical to the TRF. The combination of pole coordinates is beneficial for the CRF, whereas the combination of \(\varDelta \hbox {UT1}\) results in clear rotations of the estimated CRF. However, the standard deviations of the EOP and the CRF improve by the inter-technique combination which indicates the benefits of a common estimation of all parameters. It became evident that the common determination of TRF, EOP, and CRF systematically influences future ICRF computations at the level of several \(\upmu \)as. Moreover, the CRF is influenced by up to \(50~\upmu \)as if the station coordinates and EOP are dominated by the satellite techniques.  相似文献   

15.
We develop a method to evaluate the terrestrial reference frame (TRF) scale rate error using Global Positioning System (GPS) satellite antenna phase center offset (APCO) parameters and apply it to ITRF2008. We search for the TRF in which z-APCO parameters have the smallest drift. In order to provide realistic error bars for the z-APCO drifts, we pay attention to model periodic variations and auto-correlated noise processes in the z-APCO time series. We will show that the GPS scale rate with respect to a frame is, as a first approximation, proportional to the estimated mean z-APCO trend if that frame is used to constrain station positions. Thus, an ITRF2008 scale rate error between ?0.27 and ?0.06 mm/yr depending on the GPS analysis center can be estimated, which demonstrates the high quality of the newly constructed ITRF2008. We will also demonstrate that the traditional estimates of the GPS scale rate from 7-parameter similarity transformations are consistent with our newly derived GPS scale rates with respect to ITRF2008 within two sigmas. We find using International GNSS Service (IGS) products that the traditional approach is relevant for scale rate determination even if some of the z-APCO values supplied by the IGS were not simultaneously calibrated. As the scale rate is related to the accuracy of vertical velocities, our estimates supply a conservative evaluation that can be used for error budget computation.  相似文献   

16.
The source position time-series for many of the frequently observed radio sources in the NASA geodetic very long baseline interferometry (VLBI) program show systematic linear and non-linear variations of as much as 0.5 mas (milli-arc-seconds) to 1.0 mas, due mainly to source structure changes. In standard terrestrial reference frame (TRF) geodetic solutions, it is a common practice to only estimate a global source position for each source over the entire history of VLBI observing sessions. If apparent source position variations are not modeled, they produce corresponding systematic variations in estimated Earth orientation parameters (EOPs) at the level of 0.02–0.04 mas in nutation and 0.01–0.02 mas in polar motion. We examine the stability of position time-series of the 107 radio sources in the current NASA geodetic source catalog since these sources have relatively dense observing histories from which it is possible to detect systematic variations. We consider different strategies for handling source instabilities where we (1) estimate the positions of unstable sources for each session they are observed, or (2) estimate spline parameters or rate parameters for sources chosen to fit the specific variation seen in the position-time series. We found that some strategies improve VLBI EOP accuracy by reducing the biases and weighted root mean square differences between measurements from independent VLBI networks operating simultaneously. We discuss the problem of identifying frequently observed unstable sources and how to identify new sources to replace these unstable sources in the NASA VLBI geodetic source catalog.  相似文献   

17.
The satellites of the Global Positioning System (GPS) offer an important new geodetic resource making possible a highly accurate portable radio geodetic system. A concept called SERIES (Satellite Emission Radio Interferometric Earth Surveying) makes use of GPS radio transmissions without any satellite modifications. By employing the technique of very long baseline interferometry (VLBI) and its calibration methods, 0.5 to 3 cm three dimensional baseline accuracy can be achieved over distances of 2 to 200 km respectively, with only 2 hours of on-site data acquisition. The use of quasar referenced ARIES Mobile VLBI to establish a sparse fundamental control grid will provide a basis for making SERIES GPS measurements traceable to the time-invariant quasar directions. Using four SERIES stations deployed at previously established ARIES sites, allows the GPS satellite apparent positions to be determined. These apparent positions then serve as calibrations for other SERIES stations at unknown locations to determine their positions in a manner traceable to the quasars. Because this proposed radio interferometric configuration accomplishes its signal detection by cross-correlation, there is no dependence upon knowledge of the GPS transmitted waveforms which might be encrypted. Since GPS radio signal strengths are 105 stronger than quasar signals, a great reduction in telecommunications sophistication is possible which will result in an order of magnitude less cost for a SERIES GPS station compared to a quasar based mobile VLBI system. The virtually all-weather capability of SERIES offers cost-effective geodetic monitoring with applications to crustal dynamics and earthquake research.  相似文献   

18.
Time series of daily position solutions at eight co-located GPS and VLBI stations are used to assess the frequency features in the solutions over various time-scales. This study shows that there are seasonal and inter-annual signals in all three coordinate components of the GPS and VLBI solutions. The power and frequency of the signals vary with time, the station considered and the coordinate components, and between the GPS and VLBI solutions. In general, the magnitudes of the signals in the horizontal coordinate components (latitude and longitude) are weaker than those in the height component. The weighted means of the estimated annual amplitudes from the eight GPS stations are, respectively, 1.0, 0.8 and 3.6 mm for the latitude, longitude and height components, and are, respectively, 1.5, 0.7 and 2.2 mm for the VLBI solutions. The phases of the annual signals estimated from the GPS and VLBI solutions are consistent for most of the co-located stations. The seasonal signals estimated from the VLBI solutions are, in general, more stable than those estimated from the GPS solutions. Fluctuations at inter-annual time-scales are also found in the series. The inter-annual fluctuations are up to ∼5 mm for the latitude and longitude components, and up to ∼10 mm for the height component. The effects of the seasonal and inter-annual variations on the estimated linear rates of movement of the stations are also evaluated.  相似文献   

19.
基于全球板块运动模型分析大西洋扩张变化   总被引：1，自引：0，他引：1  
基于现代空间测量技术SLR、VLBI和GPS实测资料，解算出大西洋中脊海底扩张速率，其中北大西洋的东西向扩张速率平均为35mm/a，赤道大西洋东西向扩张速度分别为20－25mm/a，南大西洋东西向扩张速率为22－28mm/a，证实全球板块运动的存在及大西洋扩张学说，并基于全球几百万年地质模型NNR－NUVEL1A，北大西洋的东西向扩张速率平均为24．3mm/a，基于最新全球板块运动模型ITRF2000VEL，北大西洋的东西向扩张速率平均为20．8mm/a，总体上大西洋实测东西扩张速度与根据地学资料推出的地球板块运动模型和最新ITRF2000VEL模型的结果基本一致。  相似文献   

20.
This paper presents new methodology for correcting interferometric synthetic aperture radar (InSAR) deformation maps using GPS observables and products. The methodology presents a sequential procedure for correcting the errors presented in InSAR deformation maps such as troposphere delay, ionosphere delay and baseline error. The main target of this research is to measure land deformations with geodetic accuracy using only one L-band interferogram with the aid of GPS observables and products. The proposed methodology was tested on Tokyo bay area which has been affected by the 2011 Tohoku earthquake. The results were verified against deformations detected by GPS stations and geodetic triangulation network showing a standard deviation of 5.6 and 10.5 mm, respectively.  相似文献   

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