Alberta Albertella

Alberta Albertella
Politecnico di Milano | Polimi · Department of Civil and Environmental Engineering

About

84
Publications
11,592
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
559
Citations
Additional affiliations
June 2012 - present
Politecnico di Milano
Position
  • Professor (Assistant)
August 2005 - February 2012
Technische Universität München
Position
  • Researcher

Publications

Publications (84)
Article
Full-text available
The International Service for the Geoid (ISG, https://www.isgeoid.polimi.it/, last access: 31 March 2021) provides free access to a dedicated and comprehensive repository of geoid models through its website. In the archive, both the latest releases of the most important and well-known geoid models, as well as less recent or less known ones, are fre...
Preprint
Full-text available
The International Service for the Geoid (ISG, https://www.isgeoid.polimi.it/ ) provides free access to a dedicated and comprehensive repository of geoid models through its website. In the archive, both the latest releases of the most important and well-known geoid models, as well as less recent or less known ones, are freely available, giving to th...
Article
Full-text available
Open Data, and Open Government Data, are proving to be an important resource for the economic development inside the domain where information has a key role (Carrara et al., 2015). Although, different practices for data publishing have led to misalignment, underuse and repetition of information (Bizer et al., 2011). For this reason, the Public Admi...
Article
Full-text available
General ocean circulation models are not perfect. Forced with observed atmospheric fluxes they gradually drift away from measured distributions of temperature and salinity. We suggest data assimilation of absolute dynamical ocean topography (DOT) observed from space geodetic missions as an option to reduce these differences. Sea surface information...
Presentation
Full-text available
National geoid models are frequently used in engineering applications to transform GNSS derived ellipsoidal heights into orthometric heights. The establishment of a unique International Height Reference System (IHRS) among neighboring countries requires the verification of the consistency between national geoids. The choice of different reference t...
Presentation
Full-text available
The combination of altimeter data and gravity allows an effective estimation of the Mean Dynamic Topography (MDT) at sea. The MDT allows then estimating the oceanic currents, a crucial information in hydrological analysis and oceanographic studies. This is of particular interest in closed seas, such as the Mediterranean Sea, due to the impact that...
Presentation
Full-text available
The main scope of the GEOMED2 project is the determination of a high-accuracy and high-resolution geoid model for the Mediterranean Sea using land and marine gravity data and the more recent Global Geopotential Models, those based on GOCE/GRACE data. The processing methodology is based on the well-known remove-compute-restore procedure and both sto...
Presentation
Full-text available
The GEOMED2 project has been set up in order to compute an updated estimate of the geoid in the Mediterranean area. In this work, the geoid computation based on gravity data collected in the area 29o<lat.<48o -10o<lon.<41o, covering the entire Mediterranean basin, is presented. Outlier rejection and data homogenization have been carefully performed...
Article
Full-text available
The UN Open GIS Initiative is to identify and develop, under UN guidance, an Open Source GIS bundle that meets the requirements of UN operations, taking full advantage of the expertise of mission partners (partner nations, technology contributing countries, international organizations, academia, NGO’s, private sector). The project, started in 2016,...
Conference Paper
Full-text available
It is well-known that the Mediterranean Sea is challenging both in terms of geoid and Mean Dynamic Ocean Topography (MDOT) determination due to its geodynamic and oceanic features. Poor gravity data coverage and their outdated nature, along with the fact that the gravity and geoid slopes in the Mediterranean reach significant values with high varia...
Conference Paper
Full-text available
With nowadays high resolution Global Geopotential Models (GGMs), traditional geoid approximation with the Remove-Compute-Restore (RCR) procedure needs revisiting both in terms of the numerical and the methodological steps followed. This becomes evident if one considers the high degree of expansion of the latest combined GGMs, corresponding to frequ...
Poster
Full-text available
The Mediterranean Sea has always been a lab for geosciences, given its geodynamic peculiarities, the large short-scale variations of the gravity field and the complex circulation. Within the GEOMED 2 project, new improved representations of the Mediterranean marine geoid have been deemed as necessary, so that the Mean Dynamic sea surface Topography...
Presentation
Full-text available
The unique features of the Mediterranean Sea, with its large gravity variations, complex circulation, and geodynamic peculiarities have always constituted this semi-enclosed sea area as a unique geodetic, geodynamics and ocean laboratory. The main scope of the GEOMED 2 project is the collection of all available gravity, topography/bathymetry and sa...
Conference Paper
Full-text available
A statistical test has been set up to check whether the geostrophic velocities from the WiG MDT (also considering their variability) are consistent with those derived from other models (indicated with REF) in the Gulf Area. A chi-square test is defined as: where is a vector of velocities (both zonal and meridian components) evaluated in N points an...
Article
Full-text available
The GOCE satellite mission has significantly improved the results obtained with the previous satellite missions CHAMP and GRACE. Using GOCE data satellite Global Geopotential Models were developed using three different approaches, namely the direct, the time-wise and the space-wise approaches. The last releases of these models are complete to degre...
Conference Paper
Full-text available
The Mediterranean Sea has always been of economic and ecological importance to its surrounding countries. A better understanding of its currents is necessary for the management of fishery resources, potential pollution, and maritime security. Currents can be derived from the Mean Dynamic sea surface Topography (MDT), which can be estimated by subtr...
Poster
Full-text available
The GAL (Galileo for Gravity) project, founded by the European GNSS Agency (GSA) in the framework of the FP7 Transport theme aims to study and develop a state-of-art methodology for the determination of precise and high-resolution gravity field models from strapdown kinematic airborne gravimetry. In this work, the procedure applied in the framework...
Article
Physical geodesy is by definition the science which studies and calculates the Earth’s gravity field and its physical form. Satellite physical geodesy exploits satellite techniques to solve the problems established in physical geodesy. During the second half of the twentieth century, satellite techniques allowed to make outstanding advances in the...
Article
In 2012 the GEOHALO flight mission was carried out using the new German research aircraft HALO. The surveyed zone covers the Central-South part of Italy, roughly from latitude 36°N to 44°N. In this area, seven main tracks NW to SE were surveyed having a spacing of about 40 km and an altitude of 3,500 m, complemented by an eighth track in an altitud...
Article
One of the main fields of application of static gravity field models is the determination of the (geodetic) mean dynamic ocean topography (MDT) as the difference of a mean sea surface derived from multi-year satellite altimetry, and a high-resolution static geoid model. In this study the performance of several satellite-only global gravity models i...
Article
The ocean north of the Antarctic continent is one of the most dynamic ocean areas on our globe. It is also critical for the regulation of the global climate.We compute a high resolution mean dynamical ocean topography (MDT) using geodetic data and derive a detailed model of the global ocean circulation in this crucial area. The MDT is determined us...
Article
Full-text available
Absolute dynamic topography, i.e. the difference between time dependent multi-mission altimetric sea surface height and one of the most recent GOCE and GRACE based geoids, is assimilated in a global ocean general circulation model. To this end we apply an ensemble based Kalman technique, the "Error Subspace Transform Kalman Filter" (ESTKF). Here we...
Article
A mean dynamic ocean topography (MDT) has been computed using a high resolution GOCE (Gravity field and steady-state Ocean Circulation Explorer) gravity model and a new mean sea surface obtained from a combination of satellite altimetry covering the period 1992 October till 2010 April. The considered gravity model is GO-CONS-GCF-2-TIM-R3, which com...
Article
Estimation of ocean circulation is investigated via assimilation of satellite measurements of the dynamic ocean topography (DOT) into the global finite-element ocean model (FEOM). The DOT was obtained by means of a geodetic approach from carefully cross-calibrated multi-mission altimeter data and GRACE gravity fields. The spectral consistency was a...
Article
The mean dynamic topography (MDT) is defined as the difference between the mean sea surface (MSS) derived from satellite altimetry, averaged over several years, and the static geoid. Assuming geostrophic conditions, from the MDT the ocean surface velocities as important component of global ocean circulation can be derived from it. Due to the availa...
Article
Full-text available
In this work we examine the impact of assimilation of multi-mission-altimeter data and the GRACE/GOCE gravity fields into the finite element ocean model (FEOM), with the focus on the Southern Ocean circulation. In order to do so, we use the geodetic approach for obtaining the dynamical ocean topography (DOT), that combines the multi-mission-altimet...
Article
Global satellite-only gravity field models, parameterized as spherical harmonic coefficients and the corresponding full variance-covariance matrix, are computed in the frame of the ESA project "GOCE High-level Processing Facility" based only on GOCE data applying the time-wise processing method, and as combined models including also GRACE, CHAMP an...
Article
The new gravity field models, derived from the geodetic gravity missions GRACE and GOCE, give high resolution information of the earth gravity field. Using these models together with newly derived multi-mission mean sea surface it is possible to compute a geodetic mean dynamic topography (MDT) with high resolution. In particular, a detailed analysi...
Article
In 2009 the European Space Agency satellite mission GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) was launched. Its objectives are the precise and detailed determination of the Earth’s gravity field and geoid. Its core instrument, a three axis gravitational gradiometer, measures the gravity gradient components V xx , V yy , V...
Article
Full-text available
Ensemble Kalman filter methods are typically used in combination with one of two localization techniques. One technique is covariance localization, or direct forecast error localization, in which the ensemble-derived forecast error covariance matrix is Schur multiplied with a chosen correlation matrix. The second way of localization is by domain de...
Article
Full-text available
In this work we examine the impact of assimilation of multi-mission-altimeter data and the GRACE/GOCE gravity fields into the finite element ocean model (FEOM), with the focus on the Southern Ocean circulation. In order to do so, we use the geodetic approach for obtaining the dynamical ocean topography (DOT), that combines the multi-mission-altimet...
Article
Full-text available
Estimation of ocean circulation is investigated via assimilation of satellite measurements of dynamical ocean topography (DOT) into the global finite-element ocean model (FEOM). The DOT was obtained by means of geodetic approach from carefully cross-calibrated multi-mission- altimeter data and GRACE/GOCE gravity fields. The spectral consistency was...
Conference Paper
The geoid models from GRACE and soon GOCE in combination with sea surface geometry data from satellite altimetry allow to obtain a precise estimate of the absolute dynamic sea surface topography with rather high spatial resolution. However, this requires the combination of data with fundamentally different characteristics and different spatial reso...
Article
Estimation of ocean circulation via assimilation of satellite measurements of dynamical ocean topography (DOT) into the global finite-element ocean model (FEOM) is investigated. The DOT was obtained by means of geodetic approach from carefully cross-calibrated multi-mission-altimeter data and GRACE gravity fields. The spectral consistency was achie...
Article
Geoid models from the new generation of satellite gravity missions, such as GRACE and GOCE, in combination with sea surface from satellite altimetry allow to obtain absolute dynamic ocean topography with rather high spatial resolution and accuracy. However, this implies combination of data with fundamentally different characteristics and different...
Article
Full-text available
Coupled observations of GPS and levelling data are nowadays commonly available. In Italy, IGM has surveyed more than 1000 levelling points with GPS. On these GPS/levelling points, one can get the geoid undulation by simply subtracting the orthometric height from the hellipsoidal height (Heiskanen and Moritz, 1993). This large and reliable data set...
Article
Full-text available
A host of geophysical processes contribute to temporal variations in the low-degree zonal harmonics of the Earth's gravity field. The present paper focuses on atmosphere-based mass redistributions using global surface pressure data from the NOAA Climate Diagnostics Center for the period 1980-2002. We computed atmosphere-triggered temporal variation...
Conference Paper
Full-text available
It is well known that the classical testing procedures are not able to detect any significant deformation when the estimated displacements stemming from repeated surveys are small with respect to their precisions. This is true even if the displacements show some internal consistency (e.g. all the displacements have a common direction) or agree with...
Conference Paper
Full-text available
Riassunto esteso Nel controllo di deformazioni di strutture o di movimenti franosi, spesso le tecniche tradizionali di analisi statistica non sono in grado di evidenziare spostamenti significativi quando la loro entità è relativamente piccola rispetto alla precisione delle misure. Ciò accade anche in quei casi in cui gli spostamenti rilevati mostra...
Conference Paper
Full-text available
Parole chiave > Filtro di Kalman, Minimi quadrati, Navigazione, solu-zione geodetica Riassunto > Da sempre si è ritenuto il filtro di Kalman un'ottima alter-nativa alle soluzioni minimi quadrati anche per stime richieste non in tempo reale: ciò è principalmente dovuto all'insostenibile carico nume-rico che la soluzione minimi quadrati necessariamen...
Conference Paper
Full-text available
Many years ago the problem was addressed in satellite geodesy whether the collocation scheme based on covariances estimated on the rotation group, under the hypothesis of stochastic invariance of the underlying random field, could be directly applied to the time-wise data analysis, which should be typically based on a prior hypothesis of time stati...
Article
Full-text available
Working Group on Measurements and Methods of Hight Precision Space Geodesy - ASI Research (1998-1999-2000)
Article
Full-text available
An artificial satellite, flying in a purely gravitational field is a natural probe, such that, by a very accurate orbit determination, would allow a perfect estimation of the field. A true satellite experiences a number of perturbational, non-gravitational forces acting on the shell of the spacecraft; these can be revealed and accurately measured b...
Article
Full-text available
The paper deals with the problem of treating realistic GOCE data, filtered by a measurement bandwidth window applied to the time-wise stream of data. For the moment we are concentrating on the second radial derivative of the anomalous potential (Trr), since these data are the most informative and the easiest to treat analytically.
Article
Full-text available
 In the framework of a boundary value problem (BVP), when areas on the boundary are void of data the solution of the problem becomes undetermined and clearly more difficult. Physically, this could be the situation in which a gradiometer on a satellite on a perfectly circular orbit covers a sphere with measured second radial derivatives: if the sate...
Chapter
The Slepian problem consists in determining a sequence of functions that constitute an orthonormal basis of a subset of ℝ, (or ℝ2) concentrating the maximum information in the subspace of square integrable function with bandfinite spectrum. The same problem can be stated and solved on the sphere. The relation between the new basis and the ordinary...
Article
In the last two years the representation of harmonic functions defined only through data on spheres with polar caps, has been studied by the authors, using a set of functions orthonormal both on the sphere and on the data set, which is a generalization of planar Slepian functions to the spherical case. This idea can be applied for instance to deriv...
Chapter
The software elements able to produce GOCE products using either Least Squares Collocation (LSC) or the Integration approach are described. The software should be made available using a distribution system and the quality standards developed in the EU project MANICORAL. A number of problems remain unsolved, and require further investigations and so...
Chapter
The scope of WP 1 (undertaken by UCPH and POLIMI) was intended as a preparatory work for further studies along the line of the data reduction strategy based on the space-wise approach. The whole concept of the approach is to use the spatial correlation of the eld of the measurements, inherited from the correlation of the anomalous potential, to ass...
Chapter
In WP4 the problem of quality assessment for GOCE data has been studied. Basically, procedures for outliers detection and removal have been identiied, from two diierent points of view. In Sec. 4.1 the problem was studied in a track-wise approach, by the group of POLIMI. In Sec. 4.2 the problem was studied in an area-wise approach by C.C.Tscherning...
Chapter
The scope of WP 1 (undertaken by UCPH and POLIMI) was intended as a preparatory work for further studies along the line of the data reduction strategy based on the space-wise approach. The whole concept of the approach is to use the spatial correlation of the eld of the measurements, inherited from the correlation of the anomalous potential, to ass...
Chapter
In WP4 the problem of quality assessment for GOCE data has been studied. Basically, procedures for outliers detection and removal have been identiied, from two diierent points of view. In Sec. 4.1 the problem was studied in a track-wise approach, by the group of POLIMI. In Sec. 4.2 the problem was studied in an area-wise approach by C.C.Tscherning...
Chapter
Many different satellite missions are in project at the moment to estimate the global gravity field of the earth and its time variations. The principles of measurement are basically three, namely: the measurement of accurate orbit anomalies and of non gravitational forces acting on the satellite; the measurement of differential orbit anomalies and...
Chapter
SAGE is a project for a satellite accelerometric mission aimed at deterniining with high precision the low-medium coefficients of the earth gravity field and their time variations. In the international panorama, SAGE would be a prosecution of CHAMP, both in time (in case of approval, SAGE launch date would be within the year 2001) and in space (SAG...
Article
Three satellite missions to evaluate on a global scale the earth gravity field have been recently inserted in the programs of some of the most important international spatial agencies. The launches of the satellites related to each mission will be carried out in few years starting from the first months of 2000. This paper describes the problems rel...
Article
Full-text available
The Slepian problem consists of determining a sequence of functions that constitute an orthonormal basis of a subset of ℝ (or ℝ2) concentrating the maximum information in the subspace of square integrable functions with a band-limited spectrum. The same problem can be stated and solved on the sphere. The relation between the new basis and the ordin...
Article
Presented at the Workshop "International cooperation and technology transfer", Feb.15-19, 1999, Parma, Italy
Article
Full-text available
After a call for proposals from the Italian Space Agency (ASI), for small satellite missions a group of Italian research teams and industries, led by the Politecnico di Milano conceived SAGE. This mission aims at determining the gravity field of the Earth by means of high-low SST, in other words the satellite orbit is determined by GPS, while the n...
Article
Full-text available
The STEP mission has been proposed to ESA as a mission for fondamenta! physics aimed at verifying thè equivalence principle; in more recent years however it was realized that thè same mission could serve for geodetic purposes, namely for thè high resolution determination of thè gravity field of thè earth. The dates important for thè mission are: 19...
Article
Full-text available
A new satellite gradiometric mission is under study in these days at thè European Sj Agency. This mission is considered as a follow on of thè abandoned Aristoteles mission, after parenthesis of thè study on thè possibility of exploiting a fundamental physics mission, STEP, for geodetic purposes; thè name of thè new mission is GEM, Gravity Explorer...
Article
Full-text available
This Report is split in 3 paragraphs: thè first is just to recali thè main topics treated in thè previous part of thè work, while paragraphs 2, 3 contain new materia! never presented before. In §2 numerica! tests are reported showing thè aliasing effect in thè least squares estimation approach; in §3 few examples of numerical potential reconstituti...
Article
The recovery of the harmonic coefficients of the anomalous potential from a geodetic quantity sampled over a regular grid is affected by the non-exact discrete orthogonality of spherical harmonics; larger errors occur for block-average quantities owing to the non-simple behaviour of the block-average operator when applied to spherical harmonics. Fo...