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Quality assessment of SRTM C- and X-band interferometric data: Implications for the retrieval of vegetation canopy height / W.S. Walker in Remote sensing of environment, vol 106 n° 4 (28/02/2007)
[article]
Titre : Quality assessment of SRTM C- and X-band interferometric data: Implications for the retrieval of vegetation canopy height Type de document : Article/Communication Auteurs : W.S. Walker, Auteur ; J.M. Kellndorfer, Auteur ; L.E. Pierce, Auteur Année de publication : 2007 Article en page(s) : pp 428 - 448 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications
[Termes IGN] bande C
[Termes IGN] bande X
[Termes IGN] bruit (théorie du signal)
[Termes IGN] canopée
[Termes IGN] erreur de mesure
[Termes IGN] erreur relative
[Termes IGN] Etats-Unis
[Termes IGN] filtrage du bruit
[Termes IGN] hauteur des arbres
[Termes IGN] image SRTM
[Termes IGN] interféromètrie par radar à antenne synthétique
[Termes IGN] MNS SRTM
[Termes IGN] modèle numérique de surface
[Termes IGN] qualité des données
[Termes IGN] radargrammétrieRésumé : (Auteur) The Shuttle Radar Topography Mission distinguished itself as the first near-global spaceborne mission to demonstrate direct sensitivity to vertical vegetation structure. Whether this sensitivity is viewed as exploitable signal or unwanted bias, a great deal of interest exists in retrieving vegetation canopy height information from the SRTM data. This study presents a comprehensive application-specific assessment of SRTM data quality, focusing on the characterization and mitigation of two primary sources of relative vertical error: uncompensated Shuttle mast motion and random phase noise. The assessment spans four test sites located in the upper Midwestern United States and examines the dependence of data quality on both frequency, i.e., C-band vs. X-band, and the number of acquired datatakes. The results indicate that the quality of SRTM data may be higher than previously thought. Novel mitigation strategies include a knowledge-based approach to sample averaging, which has the potential to reduce phase noise error by 43 to 80%. The strategies presented here are being implemented as part of an ongoing effort to produce regional- to continental-scale estimates of vegetation canopy height within the conterminous U.S. Copyright Elsevier Numéro de notice : A2007-068 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2006.09.007 En ligne : https://doi.org/10.1016/j.rse.2006.09.007 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28433
in Remote sensing of environment > vol 106 n° 4 (28/02/2007) . - pp 428 - 448[article]Efficiency of carrier-phase integer ambiguity resolution for precise GPS positioning in noisy environments / L. Zhu in Journal of geodesy, vol 81 n° 2 (February 2007)
[article]
Titre : Efficiency of carrier-phase integer ambiguity resolution for precise GPS positioning in noisy environments Type de document : Article/Communication Auteurs : L. Zhu, Auteur ; Y.C. Lai, Auteur ; M. Shah, Auteur ; et al., Auteur Année de publication : 2007 Article en page(s) : pp 149 - 156 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] ambiguïté entière
[Termes IGN] brouillage
[Termes IGN] bruit (théorie du signal)
[Termes IGN] méthode des moindres carrés
[Termes IGN] phase GPS
[Termes IGN] positionnement par GPS
[Termes IGN] résolution d'ambiguïtéRésumé : (Auteur) Precise GPS positioning relies on tracking the carrier-phase. The fractional part of carrier-phase can be measured directly using a standard phase-locked loop, but the integer part is ambiguous and the ambiguity must be resolved based on sequential carrier-phase measurements to ensure the required positioning precision. In the presence of large phase-measurement noise, as can be expected in a jamming environment for example, the amount of data required to resolve the integer ambiguity can be large, which requires a long time for any generic integer parameter estimation algorithm to converge. A key question of interest in significant applications of GPS where fast and accurate positioning is desired is then how the convergence time depends on the noise amplitude. Here we address this question by investigating integer least-squares estimation algorithms. Our theoretical derivation and numerical experiments indicate that the convergence time increases linearly with the noise variance, suggesting a less stringent requirement for the convergence time than intuitively expected, even in a jamming environment where the phase noise amplitude is large. This finding can be useful for practical design of GPS-based systems in a jamming environment, for which the ambiguity resolution time for precise positioning may be critical. Copyright Springer Numéro de notice : A2007-048 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0096-y En ligne : https://doi.org/10.1007/s00190-006-0096-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28413
in Journal of geodesy > vol 81 n° 2 (February 2007) . - pp 149 - 156[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-07021 RAB Revue Centre de documentation En réserve L003 Disponible 266-07022 RAB Revue Centre de documentation En réserve L003 Disponible Modeling long-period noise in kinematic GPS applications / A. Borsa in Journal of geodesy, vol 81 n° 2 (February 2007)
[article]
Titre : Modeling long-period noise in kinematic GPS applications Type de document : Article/Communication Auteurs : A. Borsa, Auteur ; J.B. Minster, Auteur ; B.G. Bills, Auteur ; et al., Auteur Année de publication : 2007 Article en page(s) : pp 157 - 170 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] Bolivie
[Termes IGN] bruit (théorie du signal)
[Termes IGN] désert
[Termes IGN] erreur moyenne quadratique altimétrique
[Termes IGN] filtrage du bruit
[Termes IGN] GPS en mode cinématique
[Termes IGN] problème inverseRésumé : (Auteur) We develop and test an algorithm for modeling and removing elevation error in kinematic GPS trajectories in the context of a kinematic GPS survey of the salar de Uyuni, Bolivia. Noise in the kinematic trajectory ranges over 15 cm and is highly autocorrelated, resulting in significant contamination of the topographic signal. We solve for a noise model using crossover differences at trajectory intersections as constraints in a least-squares inversion. Validation of the model using multiple realizations of synthetic/simulated noise shows an average decrease in root-mean-square-error (RMSE) by a factor of four. Applying the model to data from the salar de Uyuni survey, we find that crossover differences drop by a factor of eight (from an RMSE of 5.6 to 0.7 cm), and previously obscured topographic features are revealed in a plan view of the corrected trajectory. We believe that this algorithm can be successfully adapted to other survey methods that employ kinematic GPS for positioning. Copyright Springer Numéro de notice : A2007-049 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0097-x En ligne : https://doi.org/10.1007/s00190-006-0097-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28414
in Journal of geodesy > vol 81 n° 2 (February 2007) . - pp 157 - 170[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-07021 RAB Revue Centre de documentation En réserve L003 Disponible 266-07022 RAB Revue Centre de documentation En réserve L003 Disponible Least-square variance component estimation / AliReza Amiri-Simkooei (2007)
Titre : Least-square variance component estimation : Theory and GPS applications Type de document : Monographie Auteurs : AliReza Amiri-Simkooei, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2007 Collection : Netherlands Geodetic Commission Publications on Geodesy, ISSN 0165-1706 num. 64 Importance : 208 p. Format : 17 x 24 cm ISBN/ISSN/EAN : 978-90-6132-301-3 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] analyse de variance
[Termes IGN] analyse multivariée
[Termes IGN] bruit blanc
[Termes IGN] bruit rose
[Termes IGN] coordonnées GPS
[Termes IGN] estimation statistique
[Termes IGN] matrice de covariance
[Termes IGN] méthode des moindres carrés
[Termes IGN] modèle stochastique
[Termes IGN] série temporelle
[Termes IGN] signal GPS
[Termes IGN] varianceIndex. décimale : 30.61 Systèmes de Positionnement par Satellites du GNSS Résumé : (Auteur) Data processing in geodetic applications often relies on the least-squares method, for which one needs a proper stochastic model of the observables. Such a realistic covariance matrix allows one first to obtain the best (minimum variance) linear unbiased estimator of the unknown parameters; second, to determine a realistic precision description of the unknowns; and, third, along with the distribution of the data, to correctly perform hypothesis testing and assess quality control measures such as reliability. In many practical applications the covariance matrix is only partly known. The covariance matrix is then usually written as an unknown linear combination of known cofactor matrices. The estimation of the unknown (co)variance components is generally referred to as variance component estimation (VCE). In this thesis we study the method of least-squares variance component estimation (LSVCE) and elaborate on theoretical and practical aspects of the method. We show that LS-VCE is a simple, flexible, and attractive VCE-method. The LS-VCE method is simple because it is based on the well-known principle of least-squares. With this method the estimation of the (co)variance components is based on a linear model of observation equations. The method is flexible since it works with a user-defined weight matrix. Different weight matrix classes can be defined which all automatically lead to unbiased estimators of (co)variance components. LS-VCE is attractive since it allows one to apply the existing body of knowledge of least-squares theory to the problem of (co)variance component estimation. With this method, one can 1) obtain measures of discrepancies in the stochastic model, 2) determine the covariance matrix of the (co)variance components, 3) obtain the minimum variance estimator of (co)variance components by choosing the weight matrix as the inverse of the covariance matrix, 4) take the a-priori information on the (co)variance component into account, 5) solve for a nonlinear (co)variance component model, 6) apply the idea of robust estimation to (co)variance components, 7) evaluate the estimability of the (co)variance components, and 8) avoid the problem of obtaining negative variance components. LS-VCE is capable of unifying many of the existing VCE-methods such as MINQUE, BIQUE, and REML, which can be recovered by making appropriate choices for the weight matrix. An important feature of the LS-VCE method is the capability of applying hypothesis testing to the stochastic model, for which we rely on the w-test, v-test, and overall model test. We aim to find an appropriate structure for the stochastic model which includes the relevant noise components into the covariance matrix. The w-test statistic is introduced to see whether or not a certain noise component is likely to be present in the observations, which consequently can be included in the stochastic model. Based on the normal distribution of the original observables we determine the mean and the variance of the w-test statistic, which are zero and one, respectively. The distribution is a linear combination of mutually independent central chi-square distributions each with one degree of freedom. This distribution can be approximated by the standard normal distribution for some special cases. An equivalent expression for the w-test is given by introducing the v-test statistic. The goal is to decrease the number of (co)variance components of the stochastic model by testing the significance of the components. The overall model test is introduced to generally test the appropriateness of a proposed stochastic model. We also apply LS-VCE to real data of two GPS applications. LS-VCE is applied to the GPS geometry-free model. We present the functional and stochastic model of the GPS observables. The variance components of different observation types, satellite elevation dependence of GPS observables’ precision, and correlation between different observation types are estimated by LS-VCE. We show that the precision of the GPS observables clearly depends on the elevation angle of satellites. Also, significant correlation between observation types is found. For the second application we assess the noise characteristics of time series of daily coordinates for permanent GPS stations. We apply LS-VCE to estimate white noise and power-law noise (flicker noise and random walk noise) amplitudes in these time series. The results confirm that the time series are highly time correlated. We also use the w-test statistic to find an appropriate stochastic model of GPS time series. A combination of white noise, autoregressive noise, and flicker noise in general best characterizes the noise in all three position components. Unmodelled periodic effects in the data are then captured by a set of harmonic functions, for which we rely on least-squares harmonic estimation (LS-HE) developed in the same framework as LS-VCE. The results confirm the presence of annual and semiannual signals, as well as other significant periodic patterns in the series. To avoid the biased estimation of the variance components, such sinusoidal signals should be included in the functional part of the model before applying LS-VCE. Note de contenu : 1. Introduction
2. Least-Squares Estimation and Validation
3. Variance Component Estimation: A Review
4. Least-Squares Variance Component Estimation
5. Detection and Validation in Stochastic Model
6. Multivariate Variance-Covariance Analysis
7. GPS Geometry-Free Model
8. GPS Coordinate Time Series
9. Conclusions and Recommendations
A. Mathematical Background
B. Derivation of Equations
C. Moments of Normally Distributed Data
D. Mixed model with hard constraints
BibliographyNuméro de notice : 15303 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62689 Réservation
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Code-barres Cote Support Localisation Section Disponibilité 15303-01 30.61 Livre Centre de documentation Géodésie Disponible Local solutions to inverse problems in geodesy: The impact of the noise covariance structure upon the accuracy of estimation / F. Bauer in Journal of geodesy, vol 81 n° 1 (January 2007)
[article]
Titre : Local solutions to inverse problems in geodesy: The impact of the noise covariance structure upon the accuracy of estimation Type de document : Article/Communication Auteurs : F. Bauer, Auteur ; P. Mathe, Auteur ; S. Pereverzev, Auteur Année de publication : 2007 Article en page(s) : pp 39 - 51 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] bruit (théorie du signal)
[Termes IGN] covariance
[Termes IGN] équation
[Termes IGN] potentiel de pesanteur terrestre
[Termes IGN] précision du positionnement
[Termes IGN] problème inverseRésumé : (Auteur) In many geoscientific applications, one needs to recover the quantities of interest from indirect observations blurred by colored noise. Such quantities often correspond to the values of bounded linear functionals acting on the solution of some observation equation. For example, various quantities are derived from harmonic coefficients of the Earth’s gravity potential. Each such coefficient is the value of the corresponding linear functional. The goal of this paper is to discuss new means to use information about the noise covariance structure, which allows order-optimal estimation of the functionals of interest and does not involve a covariance operator directly in the estimation process. It is done on the basis of a balancing principle for the choice of the regularization parameter, which is new in geoscientific applications. A number of tests demonstrate its applicability. In particular, we could find appropriate regularization parameters by knowing a small part of the gravitational field on the Earth’s surface with high precision and reconstructing the rest globally by downward continuation from satellite data. Copyright Springer Numéro de notice : A2007-038 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0049-5 En ligne : https://doi.org/10.1007/s00190-006-0049-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28404
in Journal of geodesy > vol 81 n° 1 (January 2007) . - pp 39 - 51[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-07011 RAB Revue Centre de documentation En réserve L003 Disponible 266-07012 RAB Revue Centre de documentation En réserve L003 Disponible Une topographie plus précise / Françoise de Blomac in SIG la lettre, n° 83 (janvier 2007)PermalinkError analysis of weekly station coordinates in the DORIS network / Simon D.P. Williams in Journal of geodesy, vol 80 n° 8-11 (November 2006)PermalinkEstimating the noise in space-geodetic positioning: the case of DORIS / Karine Le Bail in Journal of geodesy, vol 80 n° 8-11 (November 2006)PermalinkPlate kinematic of Nubia-Somalia using combined DORIS and GPS solution / Jean-Mathieu Nocquet in Journal of geodesy, vol 80 n° 8-11 (November 2006)PermalinkSearching for Galileo: reception and analysis of signals from GIOVE-A / M.L. Psiaki in GPS world, vol 17 n° 6 (June 2006)PermalinkÉvaluation de la qualité des séries temporelles de mesures en géodesie spatiale / Karine Le Bail in Bulletin d'information scientifique et technique de l'IGN, n° 75 (mars 2006)PermalinkPermalinkLong term consistency of multi-technique terrestrial reference frames, a spectral approach / Karine Le Bail (2006)PermalinkAssessment of very high spatial resolution satellite image segmentations / A.P. Carleer in Photogrammetric Engineering & Remote Sensing, PERS, vol 71 n° 11 (November 2005)PermalinkPrototyping a global algorithm for systematic fire-affected area mapping using MODIS time series data / D.P. Roy in Remote sensing of environment, vol 97 n° 2 (30/07/2005)Permalink