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Quality assessment of satellite-based global gravity fields models / Johannes Bouman (2000)  

Public Titre : Quality assessment of satellite-based global gravity fields models Type de document : Thèse/HDR Auteurs : Johannes Bouman, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2000 Collection : Netherlands Geodetic Commission Publications on Geodesy Sous-collection : New series num. 48 Importance : 114 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-90-6132-270-2 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] erreur moyenne quadratique [Termes IGN] erreur systématique [Termes IGN] estimation statistique [Termes IGN] qualité des données Index. décimale : 30.40 Géodésie physique Note de contenu : 1 INTRODUCTION 2 Parameter estimation and the associated mean square error 2.1 Introduction 2.2 Inverse problems and regularisation - 2.2.1 Illposed problems - 2.2.2 Global regularisation methods 2.3 Choice of regularisation parameters - 2.3.1 Minimum MSE - 2.3.2 Single regularisation parameter - 2.3.3 Multiple regularisation parameters 3 QUALITY, MEASURES 3.1 Introduction 3.2 Spherical harmonic expansion of the gravitational potential 3.3 Biased and unbiased estimation 3.4 Error propagation - 3.4.1 Full error matrix - 3.4.2 Blockdiagonal error matrix 3.5 Ratio measures 3.6 Contribution measures - 3.6.1 Contribution measure for the unbiased solution - 3.6.2 Contribution measure for the biased solution 4 GRAVITY FIELD OBSERVATIONS 4.1 Introduction 4.2 Observation model and iterative solution 4.3 Series expansion of the potential in orbital coordinates 4.4 Satellite gravity gradiometry - 4.4.1 Principle - 4.4.2 Timewise approach - 4.4.3 Blockdiagonal normal matrix 4.5 Satellite to satellite tracking - 4.5.1 Hill equations - 4.5.2 Observation equations - 4.5.3 Blockdiagonal normal matrix 4.6 Airborne gravimetry - 4.6.1 Observation model - 4.6.2 Structure of the normal matrix 5 GRAVITY FIELD MODELS FROM SGG ONLY 5.1 Introduction 5.2 Synthesis and analysis. - 5.2.1 Synthesis - 5.2.2 Analysis 5.3 Observations without noise. - 5.3.1 Circular polar orbit - 5.3.2 Circular inclined orbit - 5.3.3 Noncircular GOCE orbit 5.4 Noisy observations - 5.4.1 Tikhonov regularisation - 5.4.2 Biased estimation 6 COMBINED SOLUTIONS 6.1 Introduction 6.2 SGG results for different mission scenarios 6.3 Combination of SW, and SST 6.4 Combination of SW and airborne gravimetry 6.5 Combination of SGG, SST and gravimetry 7 CONCLUSIONS AND RECOMMENDATIONS A Compact operators and spectral decomposition. B A few remarks on local regularisation methods C Synthesis of SGG observations D Additional results Numéro de notice : 11430 Affiliation des auteurs : non IGN Autre URL associée : Complément Thématique : POSITIONNEMENT Nature : Thèse étrangère En ligne : https://www.ncgeo.nl/downloads/48Bouman_1.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54404

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The influence of data quality on the detectability of sea-level height variations / K.I. Van Onselen (2000)  

Public Titre : The influence of data quality on the detectability of sea-level height variations Type de document : Thèse/HDR Auteurs : K.I. Van Onselen, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2000 Collection : Netherlands Geodetic Commission Publications on Geodesy Sous-collection : New series num. 49 Importance : 204 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-90-6132-273-3 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] marée océanique [Termes IGN] marégramme [Termes IGN] marégraphe [Termes IGN] niveau de la mer [Termes IGN] niveau moyen des mers [Termes IGN] qualité des données [Termes IGN] série temporelle [Termes IGN] variation [Vedettes matières IGN] Altimétrie Index. décimale : 30.50 Nivellement - généralités Résumé : (Auteur) For low-lying areas like the Netherlands, an over-increasing sea level can become a serious threat. This is especially true if sea level rise accelerates, e.g., due to greenhouse-gas induced warming. To anticipate potential troubles, it is important to have a good estimate of the expected behaviour of future sea levels. This requires an accurate description of the present-day sea level variation curve and of foreseeable changes in this "natural" pattern in the near future. These changes in the behaviour of future sea levels can be based, e.g., on models predicting global change, but this is beyond the scope of this thesis. Much simplified, sea level rise over the last century could be described by a linear regression line. Accelerations of this "natural" pattern have occurred if the slope value of the regression line increases, or higher order regression coefficients are required to describe the sea-level rise curve. The better the natural sea level variation curve (as has occurred over the last century) can be determined, the easier it will be to detect a significant divergence from this curve. The objective of this thesis is to determine how well patterns in sea level height variations can be detected, given the limited quality of the data available. The objective of this thesis requires long sea level height time series. Therefore, only tide gauge data has been used and altimetry sea level height series have not been considered. Tide gauges measure sea level heights relative to the tide gauge bench marks. Consequently, the resulting sea level height time series show both variations in absolute sea level and vertical movements of the tide gauge bench marks. By monitoring the height changes between the tide gauge bench marks and a stable reference height, these relative sea level heights can (in principle) be converted into absolute sea level changes. Unfortunately, locating a reference point which is truly stable over long time spans will be extremely difficult, if not impossible. How well a specific sea level variation pattern can be detected depends on the sea level variations them-selves, the quality of the tide gauge measurements and, if applicable, the quality ofgeodetic measurements used to connect the tide gauge bench marks in height. Based on existing literature, it has been tried to gain a clear understanding of these various aspects. Unfortunately, in the literature studied on processes which can influence relative sea-level heights, (almost) no mention is made of long-periodic processes (periods over 20 years), while analysis of tide gauge records shows that long-periodic fluctuations with significant amplitudes do occur in sea level height time series. Sea level heights as used in this thesis are annual mean sea levels. The quality of these annual mean values not only depends on the quality of the tide gauge measurements, but also on the frequency of these measurements. Not only the quality of state-of-the-art techniques is important, but also of tide gauges and measuring frequencies which were used in the past. Since estimating long-term sea level variation curves requires long sea level height series, historical measurements have to be used as well. In chapter 3, an overview is given of the measuring precision and systematic errors and limitations characteristic for the six tide gauge systems commonly used during the last century. Based on information available for Dutch tide gauges, an estimate is given of how much the quality of annual mean sea levels deteriorates if mean values arc based on, e.g., mean tide levels instead of on hourly measurements. If data for a number of tide gauges is available, a common sea level variation curve, e.g., applying to the Dutch coast, can be estimated. Since tide gauge measurements are relative to the local tide gauge bench mark, any vertical movements of the tide gauges relative to one another will have introduced inconsistencies between the individual time series. These inconsistencies reduce the quality of a common sea level variation curve based on these tide gauge series. As long as tide gauges experience only secular height movements relative to one another, the common oscillation pattern can still be discerned using techniques like svd. However, the slope of the estimated common variation curve is determined by the rate of vertical movements of the individual tide gauges. If tide gauges undergo vertical movements which vary in rate and over time, the common oscillation pattern will be affected as well. By relating all sea level height series to the same reference frame (e.g., nap) internal differences in relative sea level due to vertical movements of the tide gauge bench marks are removed from the data sets. Ideally, permanent monitoring of the tide gauge bench marks is applied. Nowadays, this can be achieved by means of tips. However, in the past height differences were usually based on spirit levelling. In chapter 6, the quality of three geodetic techniques, i.e., gps, gravimetry, and spirit levelling is described. In addition, limitations of these techniques when applied to monitoring height changes of tide gauge bench marks arc discussed. Since changes in local gravity represent both variations in mass and changes in station height, gravimetry is not well suited for determining height differences. Uncertainties in height differences obtained by GPS can be reduced to within 1 cm. However, the quality of these measurements might be less in harbor areas (e.g., due to signal interference). GPS has the advantage that it allows for permanent monitoring over large distances, but measurements are only available for the last few decades. Spirit leveling can produce high precision height differences (over short distances), but is time consuming and prone to systematic errors (especially over long distances). However, leveled height differences arc often the only type of height information available. In the past, tide gauge bench marks have (hopefully) been connected to a local reference frame. Between some neighboring local height datums, height differences have occasionally been obtained as well. However, only since the second European leveling network (UELN-73), the height difference between the continent of Europe and Scandinavia and Great Britain respectively is available. These height connections consist of only a single connection line and, consequently, errors in these height differences cannot be detected by testing. In chapter 8, an indirect method is introduced for connecting vertical datums, which results in dynamic height differences between the fundamental stations in the various height datum zones. An advantage of this method is that quality information (both precision and reliability) of the estimated height differences can dc determined as well. Unfortunately, a high quality potential coefficient model is required. As a result, only if a new model (to be obtained from the planned GOCR mission) becomes available, height differences between datum zones could be derived with standard deviations of 1 cm. The quality of sea level variation curves depends on the method used to estimate these curves. A number of data analysing techniques have been tested for their suitability for working with sea level height data. Sea level height time series have a number of specific characteristics, for instance non-stationarity, data quality which is not constant for the complete time series, and a wide range of periodic fluctuations with sometimes variable frequencies and amplitudes. As a result, most of the techniques examined do not work well when applied to sea level height data. It is found that the best techniques for smoothing sea level height series are moving average smoothing and Singular Spectrum Analysis, while estimates of future sea level heights should be based on cither AR(i)MA modelling or regression. To determine how well specific sea level variation patterns can be detected, experiments with a large variety of simulated sea level height time series have been performed. These simulated time series consist of the curve which needs to be detected (e.g., a linear trend), periodic fluctuations (based on actual tide gauge data) and simulated additional errors. This can cither be inaccuracies introduced by the tide gauge equipment or the height measurements, or (uncorrected for) height variations between tide gauge bench marks. By applying regression to the simulated time series, it is examined whether or not the original sea level variation curve can be recovered. It should be noted that statistical significance of estimated regression coefficients is no guarantee that the "true" sea level variation curve is detected. For example, if linear regression is applied to a sea level series following a quadratic curve, the estimated trend value can still be statistically significant. For this reason, often trend estimates are shown as a function of an increasing number of observations. For the above mentioned example, estimated trend values will steadily increase with an increasing number of included observations. Only if the model (of a linear regression line) fits the data, and if enough observations are available, estimated trend values will stabilise around the trend value actually present in the data set. First, experiments have been performed with sea level height data for a single tide gauge. In this case, the original data relative to the tide gauge bench mark can be used. If (based on external knowledge of the behavior of the local sea level) long-periodic fluctuations could be eliminated from the data set, the detectability of a single linear regression line depends on the trend value and the noise level of the measurements. For sea level data with a trend of 1.5 mm/yr, even if a noise level of 5 cm applies, this trend can be detected if 35 observations are available. If a simulated time series contains long-periodic fluctuations based on data for tide gauge Den Helder, of the order of 90 years of observations are required before trend estimates stabilise around the actual trend value on which the data set is based. Therefore, it is concluded that long-periodic fluctuations are the main factor in determining the amount of data required to detect a linear trend in a sea level height time series. In chapter 7, using six tide gauge data sets, a common sea level variation curve for the Dutch coast is estimated. In order to eliminate deviations from this common curve caused by height variations of the tide gauge bench marks relative to one another, all tide gauges have to be connected in height to the local reference system (nap). Inaccuracies in the required height connections introduce inconsistencies between the time series. Since the actual height connection history for the tide gauges is unknown, a number of scenarios have been used to simulate height connection errors. Experiments show that the quality of the estimated common variation curve not only depends on the precision of the height measurements, but also on the time span between subsequent height connections. For higher levels of connection noise, it is more pronounced that the larger the time span between subsequent connections, the less dependable the estimated trend values will be. In order to detect future sea level rise accelerations, historical data has to be used as well. Experiments show that, if long periods have elapsed between historic height connections, the precision of future height connections is of almost no importance. Increasing the standard deviation of future height measurements from 5 mm to 2 cm, or increasing the time span between height connections from one to 10 years, hardly influences the results. Finally, for the North Sea area, the quality of spatial variation patterns which can be derived based on trend values for 18 tide gauges, is examined. A spatial pattern in sea level height variations should be based on real differences in trend values for the various locations and not on variations resulting from measuring errors and height changes between tide gauge bench marks. Based on experiments with simulated time series, the following conclusions have been made. If height connections to a local reference frame are performed every 10 years, ranges of errors in trend estimates (as a function of latitude and longitude) are three times as large as results based on annual connection of heights. As a result of, e.g., post-glacial rebound, fundamental stations in the different datum zones can experience height changes relative to one another. If the individual time series (connected to the local datums) are not corrected for these relative vertical movements, this will result in large errors in the estimated spatial variation pattern. If height differences between vertical datum zones are based on results derived for European leveling networks, resulting errors in trend values (as a function of latitude and longitude) will be much larger than those caused by the post-glacial rebound movements (of the selected fundamental stations: Amsterdam, Newlyn, and Helsingborg) itself. This same holds for differences in vertical movements obtained by GPS measurements with a standard deviation of the order of 1 mm/yr. Note de contenu : 1 INTRODUCTION Sea-level variations Objectives of this thesis Outline 2 TIDE GAUGE MEASUREMENTS Introduction Error characteristics of tide gauge instruments Sampling rate and averaging method of tide gauge readings Conclusions and recommendations 3 TECHNIQUES FOR ANALYSING SEA-LEVEL DATA Introduction Smoothing of tide gauge data Prediction of future sea levels Sea-level data for a group of tide gauges Conclusions and recommendations 4 DETECTABILITY OF CURVES IN RELATIVE SEA LEVEL Introduction Estimating curves in individual time series General structure of simulated data sets " Ideal " measurement series Time series containing short-periodic fluctuations Time series containing short- and long periodic fluctuations Conclusions and recommendations 5 CONNECTING TIDE GAUGES TO A LOCAL HEIGHT SYSTEM Introduction Problems related to the different " height " systems Error characteristics of measuring techniques Selection of observation sites Required sampling and time span of measurements 6 DETECTABILITY OF CURVES IN SEA LEVEL RELATIVE TO A LOCAL DATUM Introduction General structure of simulated data sets Same trend throughout the time series Transition to higher trend at the beginning of the time series Transition to higher trend at the end of the time series Conclusions and recommendations 7 REGIONAL HEIGHT DATUM CONNECTION Introduction Adding datum shifts to a geodetic boundary value problem Least squares solution of a vertical datum connection A-priori covariance matrices Datum connection in North-West Europe " Ideal " cap size for terrestrial gravity measurements Influence of the number of stations Conclusions and recommendations 8 SEA-LEVEL VARIATION PATTERNS Introduction General structure of simulated data sets Inconsistencies in annual mean values Inconsistencies introduced by local height connections Height datums experience linear movements Vertical datum connection Conclusions and recommendations 9 CONCLUSIONS AND RECOMMENDATIONS Conclusions General remarks concerning sea-level monitoring Recommendations for future research A Information concerning tide gauge stations B Derivations C Additionnal information concerning common variations curves Numéro de notice : 11431 Affiliation des auteurs : non IGN Autre URL associée : Complément Thématique : POSITIONNEMENT Nature : Thèse étrangère DOI : sans En ligne : https://www.ncgeo.nl/downloads/49VanOnselen_1.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54405

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Time in GIS: issues in spatio-temporal modelling / Luc Heres (2000)  

Public Titre : Time in GIS: issues in spatio-temporal modelling : [papers for the workshop on the theory and practice of time and history in GIS on 18 May 2000, organized by the Subcommission Geo-Information Models of the Netherlands Geodetic Commission] Type de document : Actes de congrès Auteurs : Luc Heres, Éditeur scientifique Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2000 Collection : Netherlands Geodetic Commission Publications on Geodesy Sous-collection : New series num. 47 Conférence : NGC 2000, workshop on the theory and practice of time and history in GIS 18/05/2000 Delft Pays-Bas Importance : 66 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-90-6132-269-6 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes d'information géographique [Termes IGN] cadastre [Termes IGN] données spatiotemporelles [Termes IGN] modélisation [Termes IGN] système d'information géographique [Termes IGN] temps Résumé : (éditeur) Most Geographic Information Systems started as a substitute for loose paper maps. These paper maps did not have a built-in time dimension and could only represent history indirectly as a sequence of physically separate images. This was in fact imitated by these first generation systems. The time dimension could only be represented by means of separate files. A minority of Geographic Information Systems however, started their life as a substitute for ordered lists and tables with a link to paper maps. In these lists, the inclusion of a time com-ponent in the form of a data field was quite usual. This method too was copied by the systems that replaced these paper tables. The current trend in the development of Geographic Information Systems is towards the inte-gration of the classical map-oriented concepts with the table-oriented concepts. This often leads to the explicit embedding of the time component in the GIS environment. The Subcommission Geo-Information Models of the Netherlands Geodetic Commission has organized a workshop to discuss the theory and practice of time and history in GIS on 18 May 2000. This publication contains 6 articles prepared for the workshop. The first paper, written by Donna Peuquet, gives a bird’s-eye view of the current state of the art in spatio-temporal database technology and methodology. She is a well-known expert in the field of spatio-temporal information systems and the author of many articles in this field. The second article is written by Monica Wachowicz. She describes what you can do with a GIS once it contains a historical dimension and how you can detect changes in geographic phenomena. Furthermore, her article suggests how geographic visualisation and knowledge discovery techniques can be integrated in a spatio-temporal database. How to record the time dimension in a database is one thing, how to show this dimension to users is another one. In his contribution, Menno-Jan Kraak first tells about the techniques, which were used in the age of paper maps and the limitations these methods had. He goes on to explain what kind of cartographic techniques have been developed since the mass introduc-tion of the computer. Finally he describes the powerful animation methods which currently exist and can be used on CD-ROM and Internet applications. Peter van Oosterom describes how the time dimension is represented in the information sys-tems of the Cadastre and how this is used to publish updates. The Cadastre has a very long tradition in incorporating the time component, which has always been an inherent component of the cadastral registration. In former times this was translated in very precise procedures about how to update the paper maps and registers. Today it is translated in spatio-temporal database design. The article of Luc Heres tells about the time component in the National Road Database, origi-nally designed for traffic accident registration. This is one of the systems with ''table'' roots and with quite a long tradition in handling the time dimension. He elucidates first the core objects in the conceptual model and how time is added. Next, how this model is translated in a logical design and finally how this is technically implemented. Geologists and geophysicians also have a respectable tradition in handling the time dimension in the data they collect. This is illustrated in the last paper, which is written by Ipo Ritsema. He outlines how time is handled in geological and geophysical databases maintained by TNO. By means of some practical cases he illustrates which problems can be encountered and how these can be solved. Note de contenu : - Time in GIS: Issues in spatio-temporal modelling / Luc Heres - Space-time representation: An overview / Donna J. Peuquet - The role of geographic visualisation and knowledge discovery in spatio-temporal data modelling / Monica Wachowicz - Visualisation of the time dimension / Menno-Jan Kraak - Time in cadastral maps / Peter van Oosterom - Hodochronologics: History and time in the National Road Database / Luc Heres - Time in relation to geoscientific data / Ipo Ritsema Numéro de notice : 69594 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Actes DOI : sans En ligne : https://www.ncgeo.nl/downloads/47Heres.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62238

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Knowledge-based interpretation of aerial images for updating of road maps / Marlies de Gunst (1996)  

Public Titre : Knowledge-based interpretation of aerial images for updating of road maps Type de document : Thèse/HDR Auteurs : Marlies de Gunst, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 1996 Collection : Netherlands Geodetic Commission Publications on Geodesy Sous-collection : New series num. 44 Importance : 184 p. Format : 21 x 27 cm ISBN/ISSN/EAN : 978-90-6132-259-7 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Photogrammétrie numérique [Termes IGN] carte routière [Termes IGN] extraction automatique [Termes IGN] image numérisée [Termes IGN] mise à jour cartographique [Termes IGN] modèle orienté objet [Termes IGN] photographie aérienne [Termes IGN] réseau routier [Termes IGN] route Index. décimale : 33.30 Photogrammétrie numérique Numéro de notice : 61723 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Thèse étrangère DOI : sans En ligne : https://www.ncgeo.nl/index.php/en/publicatiesgb/publications-on-geodesy/item/255 [...] Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=60974

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61723-02	33.30	Livre	Centre de documentation	Photogrammétrie - Lasergrammétrie	Disponible
61723-03	THESE	Livre	Centre de documentation	Thèses	Disponible

Methods for the generalization of geo-databases / Martien Molenaar (1996)  

Public Titre : Methods for the generalization of geo-databases Type de document : Monographie Auteurs : Martien Molenaar, Éditeur scientifique Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 1996 Collection : Netherlands Geodetic Commission Publications on Geodesy Sous-collection : New series num. 43 Importance : 72 p. Format : 21 x 30 cm Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] agrégation spatiale [Termes IGN] base de données localisées [Termes IGN] généralisation automatique de données [Termes IGN] modèle orienté objet [Termes IGN] système d'information géographique [Vedettes matières IGN] Généralisation Note de contenu : - Aggregation objectives and related decision functions / Ferjan Ormeling - The role of topologic and hierarchical spatial object models in database generalization / Martien Molenaar - Applying reactive data structures in an interactive multi-scale GIS / Peter van Oosterom and Vincent Schenkclaars - Application-oriented generalization of area objects / Arnold Bregt and Jandirk Bulens - Applying aggregations in policy support research at RIVM / Arthur van Beurden Numéro de notice : 63959 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Recueil / ouvrage collectif DOI : sans En ligne : https://www.ncgeo.nl/downloads/43Molenaar.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=44375

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63959-02	39.20	Livre	Centre de documentation	En réserve M-103	Disponible

Geodetic dual-frequency GPS receivers under anti-spoofing / P.G. Sluiter (1995)  

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Global gravity field modelling using satellite gravity gradiometry / Radboud Koop (1993)  

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Least squares filtering and testing for geodetic navigation applications / Martin H. Salzmann (1993)  

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Spherical harmonic analysis of satellite gradiometry / Reiner Rummel (1993)  

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Proceedings of the symposium refraction of transatmospheric signals in geodesy / J.C. de Munck (1992)  

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A quality investigation of global vertical datum connection / Xu Peiliang (1991)  

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The geodetic boundary value problem in two dimensions and its iterative solution / Martin Van Gelderen (1991)  

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The role of orbit errors in processing of satellite altimeter data / E.J.O. Schrama (1989)  

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NavGrav, navigation and gravimetric experiment, at the North Sea / R.H.N. Haagmans (1988)  

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On the principles, assumptions and methods of geodetic very long baseline interferometry / Frits J.J. Brouwer (1985)  

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