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Evaluation of methods for connecting InSAR to a terrestrial reference frame in the Latrobe Valley, Australia / P.J. Johnston in Journal of geodesy, vol 95 n° 10 (October 2021)  

Public [article]  inJournal of geodesy > vol 95 n° 10 (October 2021) . - n° 115 Titre : Evaluation of methods for connecting InSAR to a terrestrial reference frame in the Latrobe Valley, Australia Type de document : Article/Communication Auteurs : P.J. Johnston, Auteur ; M. S. Filmer, Auteur ; Thomas Fuhrmann, Auteur Année de publication : 2021 Article en page(s) : n° 115 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] Australian Geodetic Datum [Termes IGN] Australie [Termes IGN] Continuously Operating Reference Station network [Termes IGN] image Sentinel-SAR [Termes IGN] incertitude de mesurage [Termes IGN] interféromètrie par radar à antenne synthétique [Termes IGN] International Terrestrial Reference Frame [Termes IGN] littoral [Termes IGN] propagation d'erreur [Termes IGN] réseau géodésique permanent [Termes IGN] station GNSS [Termes IGN] subsidence Résumé : (auteur) Deformation measurements from satellite-borne synthetic aperture radar interferometry (InSAR) are usually measured relative to an arbitrary reference point (RP) of assumed stability over time. For InSAR rates to be reliably interpreted as uplift or subsidence, they must be connected to a defined Earth-centred terrestrial reference frame (TRF), usually made through GNSS continuously operating reference stations (CORS). We adapt and compare three methods of TRF connection proposed by different studies which we term the single CORS RP (SCRP), plane-fit multiple CORS (PFMC), and the multiple CORS RP (MCRP). We generalise equations for these methods, and importantly, develop equations to propagate InSAR and GNSS uncertainties through the transformation process. This is significant, because it is important to not only estimate the InSAR uncertainties, but also to account for the uncertainties that are introduced when connecting to the CORS so as to better inform our interpretation of the deformation field and the limitation of the measurements. We then test these methods using Sentinel-1 data in the Latrobe Valley, Australia. These results indicate that differences among the three TRF connection methods may be greater than their estimated uncertainties. MCRP appears the most reliable method, although it may be limited in large study areas with sparse CORS due to long wavelength InSAR errors and that gaps and/or steps may appear at the spatial limit from the CORS. SCRP relies on the quality of the single CORS connection, but can be validated by unconnected CORS in the study area. The PFMC method is suited to larger areas undergoing slow, constant deformation covering large spatial extents where there are evenly distributed CORS across the study area. Selecting an optimal method of TRF connection is dependent on local site conditions, CORS network geometry and the characteristics of the deformation field. Hence, the choice of TRF connection method should be carefully considered, because different methods may result in significantly different transformed deformation rates. We confirm slow subsidence across the Latrobe Valley relative to the vertical component of the ITRF2014, with localised high subsidence rates near open cut mining activities. Subsidence of ~ -6 mm/year is observed in the adjacent coastal region which may exacerbate relative sea level rise along the coastline, increasing future risks of coastal inundation. Numéro de notice : A2021-749 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s00190-021-01560-2 Date de publication en ligne : 08/10/2021 En ligne : https://doi.org/10.1007/s00190-021-01560-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98730 [article]

The first Australian gravimetric quasigeoid model with location-specific uncertainty estimates / Will E. Featherstone in Journal of geodesy, vol 92 n° 2 (February 2018)  

Public [article]  inJournal of geodesy > vol 92 n° 2 (February 2018) . - pp 149 - 168 Titre : The first Australian gravimetric quasigeoid model with location-specific uncertainty estimates Type de document : Article/Communication Auteurs : Will E. Featherstone, Auteur ; Jack C. McCubbine, Auteur ; Nicholas J. Brown, Auteur ; S.J. Claessens, Auteur ; M. S. Filmer, Auteur ; J.F. Kirby, Auteur Année de publication : 2018 Article en page(s) : pp 149 - 168 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] Australie [Termes IGN] géoïde gravimétrique [Termes IGN] géoïde local [Termes IGN] propagation d'erreur [Termes IGN] quasi-géoïde Résumé : (Auteur) We describe the computation of the first Australian quasigeoid model to include error estimates as a function of location that have been propagated from uncertainties in the EGM2008 global model, land and altimeter-derived gravity anomalies and terrain corrections. The model has been extended to include Australia’s offshore territories and maritime boundaries using newer datasets comprising an additional ∼280,000 land gravity observations, a newer altimeter-derived marine gravity anomaly grid, and terrain corrections at 1′′×1′′ resolution. The error propagation uses a remove–restore approach, where the EGM2008 quasigeoid and gravity anomaly error grids are augmented by errors propagated through a modified Stokes integral from the errors in the altimeter gravity anomalies, land gravity observations and terrain corrections. The gravimetric quasigeoid errors (one sigma) are 50–60 mm across most of the Australian landmass, increasing to ∼100 mm in regions of steep horizontal gravity gradients or the mountains, and are commensurate with external estimates. Numéro de notice : A2018-059 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-017-1053-7 En ligne : https://doi.org/10.1007/s00190-017-1053-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89392 [article]

Variance component estimation uncertainty for unbalanced data: application to a continent-wide vertical datum / M. S. Filmer in Journal of geodesy, vol 88 n° 11 (November 2014)  

Public [article]  inJournal of geodesy > vol 88 n° 11 (November 2014) . - pp 1081-1093 Titre : Variance component estimation uncertainty for unbalanced data: application to a continent-wide vertical datum Type de document : Article/Communication Auteurs : M. S. Filmer, Auteur ; Will E. Featherstone, Auteur ; S.J. Claessens, Auteur Année de publication : 2014 Article en page(s) : pp 1081-1093 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] analyse de variance [Termes IGN] continent [Termes IGN] incertitude des données [Termes IGN] système de référence géodésique Résumé : (Auteur) Variance component estimation (VCE) is used to update the stochastic model in least-squares adjustments, but the uncertainty associated with the VCE-derived weights is rarely considered. Unbalanced data is where there is an unequal number of observations in each heterogeneous data set comprising the variance component groups. As a case study using highly unbalanced data, we redefine a continent-wide vertical datum from a combined least-squares adjustment using iterative VCE and its uncertainties to update weights for each data set. These are: (1) a continent-wide levelling network, (2) a model of the ocean’s mean dynamic topography and mean sea level observations, and (3) GPS-derived ellipsoidal heights minus a gravimetric quasigeoid model. VCE uncertainty differs for each observation group in the highly unbalanced data, being dependent on the number of observations in each group. It also changes within each group after each VCE iteration, depending on the magnitude of change for each observation group’s variances. It is recommended that VCE uncertainty is computed for VCE updates to the weight matrix for unbalanced data so that the quality of the updates for each group can be properly assessed. This is particularly important if some groups contain relatively small numbers of observations. VCE uncertainty can also be used as a threshold for ceasing iterations, as it is shown—for this data set at least—that it is not necessary to continue time-consuming iterations to fully converge to unity. Numéro de notice : A2014-564 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-014-0744-6 Date de publication en ligne : 24/07/2014 En ligne : https://doi.org/10.1007/s00190-014-0744-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=74750 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2014111	SL	Revue	Centre de documentation	Revues en salle	Disponible

Using models of the ocean's mean dynamic topography to identify errors in coastal geodetic levelling / M. S. Filmer in Marine geodesy, vol 37 n° 1 (March - May 2014)  

Public [article]  inMarine geodesy > vol 37 n° 1 (March - May 2014) . - pp 47 - 64 Titre : Using models of the ocean's mean dynamic topography to identify errors in coastal geodetic levelling Type de document : Article/Communication Auteurs : M. S. Filmer, Auteur Année de publication : 2014 Article en page(s) : pp 47 - 64 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Nivellement [Termes IGN] données GNSS [Termes IGN] geoïde marin [Termes IGN] littoral [Termes IGN] niveau moyen des mers [Termes IGN] nivellement géodésique [Termes IGN] quasi-géoïde [Termes IGN] trait de côte Résumé : (Auteur) Identifying errors (blunders and systematic errors) in coastal geodetic levelling networks has often been problematic, primarily for two reasons. First, mean sea level (MSL) at tide gauges cannot be directly compared to height differences from levelling because the geoid/quasigeoid and MSL are not parallel, being separated by the ocean's mean dynamic topography (MDT). Second, there is a the lack of redundancy at the edge of the levelling network. This article sets out a methodology to independently identify blunders and/or systematic errors (over long distances) in geodetic levelling using MDT models to account for the separation between the geoid/quasigeoid and MSL at tide gauges. This method is then tested in a case study using an oceanographic MDT model, MSL observations, GNSS data, and a quasigeoid model. The results are significant because the errors found could not be detected by standard levelling misclosure checks alone, with supplementary data from an MDT model, with cross-validation from GNSS-quasigeoid allowing their detection. In addition, it appears that an oceanographic-only MDT is as effective as GNSS and a quasigeoid model for detecting levelling errors, which could be particularly useful for countries with coastal levelling errors in their levelling networks that cannot be identified by conventional levelling closure checks. Numéro de notice : A2015-163 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2013.868383 Date de publication en ligne : 29/10/2010 En ligne : https://doi.org/10.1080/01490419.2013.868383 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=75850 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
230-2014011	RAB	Revue	Centre de documentation	En réserve L003	Disponible