| Titre : |
Sub-daily parameter estimation in VLBI data analysis : Dissertation carried out in order to obtain the academic degree ”doctor of the technical sciences” under the supervision of o.Univ.-Prof. Dipl.-Ing. Dr.techn. Harald Schuh, presented at the Vienna University of Technology, Faculty of Mathematics and Geoinformation, Institute of Geodesy and Geophysics |
| Type de document : |
Thèse/HDR |
| Auteurs : |
Kamil Teke, Auteur ; Harald Schuh, Directeur de thèse |
| Editeur : |
Vienne [Autriche] : Vienna University of Technology |
| Année de publication : |
2011 |
| Importance : |
275 p. |
| Format : |
21 x 30 cm |
| Note générale : |
Bibliographie
thèse étrangère |
| Langues : |
Anglais (eng) |
| Descripteur : |
[Vedettes matières IGN] Géodésie spatiale
[Termes IGN] analyse comparative
[Termes IGN] compensation par moindres carrés
[Termes IGN] données ITGB
[Termes IGN] estimation des paramètres
[Termes IGN] estimation statistique
[Termes IGN] horloge
[Termes IGN] propagation troposphérique
[Termes IGN] rotation de la Terre
|
| Index. décimale : |
THESE Thèses et HDR |
| Résumé : |
(Auteur) The main objective of the work carried out within the scope of this thesis is the contribution to the VLBI2010 project of the International Very Long Baseline Interferometry (VLBI) Service for Geodesy and Astrometry (IVS) by means of developing a parameter estimation module (vie lsm) of Vienna VLBI Software (VieVS) which is capable of estimating accurate sub-daily VLBI geodetic parameters. The vie lsm module is based on the classical Gauss Markoff Least-Squares (LS) adjustment method by using continuous piece-wise linear offset (CPWLO) functions which are estimated at unique epochs, e.g. at integer hours, or at integer fractions or integer multiples of integer hours. The interval for CPWLO modelling of the parameters is usually set to values between one day to five minutes.
To investigate the sub-daily tidal motions of the VLBI antennas during IVS-CONT05, hourly CPWLO Terrestrial Reference Frame (TRF) coordinates of the antennas were estimated. Although all tidal displacements are computed from state-of-the-art geophysical models and reduced from the observations a priori to the adjustment, the radial amplitudes from the estimated hourly antenna coordinates can reach up to 1 cm (Kokee, HartRAO, Gilcreek, Westford, Svetloe, and Wettzell). To analyze the high frequency (sub-daily) Earth rotation parameter (HF-ERP) estimates of VieVS during IVS-CONT08, hourly CPWLO ERP were estimated. The Fourier spectra of the hourly VLBI and Global Positioning System (GPS) ERP estimates and the HFERP models during IVS-CONT08 are in a good agreement at prograde and retrograde 12 hours both for length of day (LOD) and polar motion. However, at 24 hour prograde polar motion the amplitude from GPS is larger by about 100 ìas than VLBI and larger by about 160 ìas than HF-ERP models. Additionally, VieVS LOD and polar motion estimates are noisier than from GPS. This may be due to the fact that no relative constraints between the CPWLO ERP estimates in VLBI analysis were introduced. The estimation of hourly source coordinates was rather intended as test study. As long as hourly CPWLO coordinates of two sources are estimated and the remaining sources are fixed to their a priori Celestial Reference Frame (CRF) i coordinates, parametrization of the Earth Orientation Parameters (EOP) is not critical for the estimated source coordinates. However, investigations on this issue need to be carried out in future, e.g. a lot can be learned from correlations between hourly source coordinates and the observation geometry.
The second aim of this thesis, which is also a very good test of the CPWLO estimates of troposphere zenith delays and gradients, is the contribution to combination studies in the framework of the Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG) by multi-technique comparison of zenith total delays (ZTD) and troposphere gradients. In the scope of this issue, VLBI VieVS estimates of troposphere ZTD and gradients during IVS-CONT08 were compared with those derived from observations with the GPS, Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and water vapor radiometers (WVR) co-located with the VLBI radio telescopes. ZTD and gradients estimated by space geodetic techniques are compared to those computed by ray-tracing through the profiles of various Numerical Weather Models (NWM), such as the European Centre for Medium-Range Weather Forecasts (ECMWF) (all sites), the Japan Meteorological Agency (JMA) and Cloud Resolving Storm Simulator (CReSS) (Tsukuba in Japan), and the High Resolution Limited Area Model (HIRLAM) (European sites). The best inter space geodetic technique agreement of ZTD during IVS-CONT08 is found between the combined IVS and the International GNSS Service (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 IVS-CONT08 in comparison to IVS-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 observable. However, the best inter-technique agreement is found between the IVS combined gradients and the GPS solutions with standard deviations between 0.2 mm and 0.7 mm. As mentioned before all the comparisons and validation tests on the troposphere products during IVS-CONT08 presented in this thesis provide important information with respect to the planned combination and integration of various observing techniques in the framework of the Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG). |
| Note de contenu : |
1 Introduction
1.1 VLBI Basics
1.2 Contribution of the thesis and research objectives
1.3 Outline of the thesis
2 VLBI delay model
2.1 Gravitational delay
2.2 Vacuum delay and geometric delay
2.3 Partial derivatives of the VLBI delay model with respect to EOP, antenna and source coordinates
2.4 Continuous piece-wise linear offset (CPWLO) functions for sub-daily parameter estimation
3 Least Squares (LS) Adjustment
3.1 Gauss Markoff model
3.2 Constraining parameters
3.3 Free Network Solution
3.4 Stacking normal equation systems
3.5 Parameter estimation in vie lsm
3.5.1 Handling outliers
4 VLBI clock error
4.1 Modelling and estimating VLBI clock errors based on CPWLO functions
4.1.1 Clock error model
4.1.2 Determining and modelling clock breaks
4.1.3 Clock break error on the VLBI observations and its propagation on estimated VLBI parameters
4.2 Frequency stabilities of the VLBI clocks
5 Troposphere delay
5.1 Troposphere mapping functions
5.2 Troposphere gradients
5.3 Troposphere delays in VieVS
6 Multi-technique comparison of troposphere zenith delays and gradients during IVSCONT
6.1 IVS-CONT08 co-located sites, techniques and solutions
6.1.1 Space geodetic solutions
6.1.2 Water Vapor Radiometer (WVR)
6.1.3 Numerical Weather Models (NWM)
6.2 Agreement criteria for the comparisons and troposphere ties
6.3 Intra-technique comparisons of ZTD
6.4 Inter-technique comparisons of ZTD
6.5 Comparison with IVS-CONT02
6.6 Troposphere gradients comparisons
7 VLBI Baseline Length Repeatability Tests of IVS-R1 and -R4 Sessions
7.1 IVS-R1 and -R4 sessions
7.2 Comparison of baseline length repeatabilities derived from different mapping functions and cut-off angles
8 Analyses of the TRF, EOP, and CRF VLBI estimates
8.1 Analysis of the tidal motions at VLBI antennas: Sub-daily CPWLO coordinate estimates versus tide models during IVS-CONT05
8.2 Analyses of the sub-daily ERP during IVS-CONT08: model versus observations
8.3 Analyses of the sub-daily coordinate time series of several defining sources in ICRF2 during IVS-CONT08
9 Conclusions and Outlook |
| Numéro de notice : |
14249 |
| Affiliation des auteurs : |
non IGN |
| Thématique : |
POSITIONNEMENT |
| Nature : |
Thèse étrangère |
| DOI : |
sans |
| En ligne : |
https://repositum.tuwien.at/handle/20.500.12708/982 |
| Format de la ressource électronique : |
URL |
| Permalink : |
https://documentation.ensg.eu/index.php?lvl=notice_display&id=62653 |
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Sub-daily parameter estimation in VLBI data analysis (2011)
