Federal Agency for Cartography and Geodesy BKG

Frankfurt am Main, Germany

Federal Agency for Cartography and Geodesy BKG

Frankfurt am Main, Germany
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Kenyeres A.,FOMI Satellite Geodetic Observatory | Sacher M.,Federal Agency for Geodesy and Cartography | Ihde J.,Federal Agency for Cartography and Geodesy BKG | Denker H.,Leibniz University of Hanover | Marti U.,Federal Office of Topography
International Association of Geodesy Symposia | Year: 2010

EUREF, the Sub-commission for the Euro-pean Reference Frame within IAG Commission 1, in cooperation with the European Geoid and Gravity Project (EGGP), is developing a homogeneous continental GPS/leveling database. EUVN_DA, the Densification Action of the EUVN (European Unified Vertical Reference Network) project is designed to support the development of the new European geoid solutions and to contribute to the realization of an accurate continental height reference surface. The cm-accuracy GPS/leveling database could also be used for the realization of the European Vertical Reference System (EVRS) and for the analysis of the national height networks. The establishment of the EUVN_DA network was started in 2003. The database now consists of about 1,500 high quality GPS/leveling points contributed from 25 countries. The GPS coordinates refer to the realizations of the ETRS89 and the leveling data to EVRS2007. Most of the EUVN_DA benchmarks are integrated into the UELN (United European Leveling Network) to assure the long term homogeneity and consistency of the height information. The GPS database mostly relies on existing measurements which fulfilled pre-defined quality requirements. The main phase of the project terminates by the end of 2008, but the periodic maintenance of the database is planned on long term. This paper summarizes the activities within the EUVN_DA project, gives an overview on the actual status and presents the results on the analysis of the continental geoid solutions. © Springer-Verlag Berlin Heidelberg 2010.

Glaser S.,TU Berlin | Konig R.,German Research Center for Geosciences | Ampatzidis D.,German Research Center for Geosciences | Ampatzidis D.,Federal Agency for Cartography and Geodesy BKG | And 6 more authors.
Journal of Geodesy | Year: 2017

In this study, we assess the impact of two combination strategies, namely local ties (LT) and global ties (GT), on the datum realization of Global Terrestrial Reference Frames in view of the Global Geodetic Observing System requiring 1 mm-accuracy. Simulated Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) data over a 7 year time span was used. The LT results show that the geodetic datum can be best transferred if the precision of the LT is at least 1 mm. Investigating different numbers of LT, the lack of co-located sites on the southern hemisphere is evidenced by differences of 9 mm in translation and rotation compared to the solution using all available LT. For the GT, the combination applying all Earth rotation parameters (ERP), such as pole coordinates and UT1-UTC, indicates that the rotation around the Z axis cannot be adequately transferred from VLBI to SLR within the combination. Applying exclusively the pole coordinates as GT, we show that the datum can be transferred with mm-accuracy within the combination. Furthermore, adding artificial stations in Tahiti and Nigeria to the current VLBI network results in an improvement in station positions by 13 and 12%, respectively, and in ERP by 17 and 11%, respectively. Extending to every day VLBI observations leads to 65% better ERP estimates compared to usual twice-weekly VLBI observations. © 2017 Springer-Verlag Berlin Heidelberg

Guntner A.,Helmholtz Center Potsdam | Guntner A.,University of Potsdam | Reich M.,Helmholtz Center Potsdam | Mikolaj M.,Helmholtz Center Potsdam | And 2 more authors.
Hydrology and Earth System Sciences | Year: 2017

In spite of the fundamental role of the landscape water balance for the Earth's water and energy cycles, monitoring the water balance and its components beyond the point scale is notoriously difficult due to the multitude of flow and storage processes and their spatial heterogeneity. Here, we present the first field deployment of an iGrav superconducting gravimeter (SG) in a minimized enclosure for long-term integrative monitoring of water storage changes. Results of the field SG on a grassland site under wet-temperate climate conditions were compared to data provided by a nearby SG located in the controlled environment of an observatory building. The field system proves to provide gravity time series that are similarly precise as those of the observatory SG. At the same time, the field SG is more sensitive to hydrological variations than the observatory SG. We demonstrate that the gravity variations observed by the field setup are almost independent of the depth below the terrain surface where water storage changes occur (contrary to SGs in buildings), and thus the field SG system directly observes the total water storage change, i.e., the water balance, in its surroundings in an integrative way. We provide a framework to single out the water balance components actual evapotranspiration and lateral subsurface discharge from the gravity time series on annual to daily timescales. With about 99 and 85% of the gravity signal due to local water storage changes originating within a radius of 4000 and 200m around the instrument, respectively, this setup paves the road towards gravimetry as a continuous hydrological field-monitoring technique at the landscape scale. © Author(s) 2017.

Bitharis S.,Aristotle University of Thessaloniki | Ampatzidis D.,Federal Agency for Cartography and Geodesy BKG | Pikridas C.,Aristotle University of Thessaloniki
Annals of Geophysics | Year: 2017

In this study the theoretical and practical approach of an optimal geodetic reference frame realization is described in detail. The Hellenic area due to its strong geodynamic behavior creates a rather inhomogeneous velocity field. This issue plays a critical role in stable and long-term geodetic datum. The methodology of the Minimization of the Kinetic Energy Criterion (MKEC) is defined and analyzed on a permanent GNSS network consisting of 151 stations. The site velocity values were estimated from seven years of continuous data. The application formula shows that the kinematic energy is minimized more than 60 percent in two different approaches for the International Terrestrial Reference Frame and the European Terrestrial Reference System 1998 (ETRS89). In addition, the realization of the ETRS89 approach in Greece is not offering any significant advantage. However, we proposed a new strategy, which minimizes the total kinetic energy and it is found effective in local areas with strong geodynamic activity like the Greece case. © 2017 by Istituto Nazionale di Geofisica e Vulcanologia. All rights reserved.

Crossley D.J.,Washington University in St. Louis | Boy J.-P.,University of Strasbourg | Hinderer J.,University of Strasbourg | Jahr T.,Friedrich - Schiller University of Jena | And 4 more authors.
Geophysical Journal International | Year: 2014

The paper in question by Van Camp and co-authors [MVC] challenges previous work showing that ground gravity data arising from hydrology can provide a consistent signal for the comparison with satellite gravity data. The data sets used are similar to those used previously, that is, the gravity field as measured by the GRACE satellites versus ground-based data from superconducting gravimeters (SGs) over the same continental area, in this case Central Europe. One of the main impediments in this paper is the presentation that is frequently confusing and misleading as to what the data analysis really shows, for example, the irregular treatment of annual components that are first subtracted then reappear in the analysis. More importantly, we disagree on specific points. Two calculations are included in our comment to illustrate where we believe that the processing in [MVC] paper is deficient. The first deals with their erroneous treatment of the global hydrology using a truncated spherical harmonic approach which explains almost a factor 2 error in their computation of the loading. The second shows the effect of making the wrong assumption in the GRACE/hydrology/surface gravity comparison by inverting the whole of the hydrology loading for underground stations. We also challenge their claims that empirical orthogonal function techniques cannot be done in the presence of periodic components, and that SG data cannot be corrected for comparisons with GRACE data. The main conclusion of their paper, that there is little coherence between ground gravity stations and this invalidates GRACE comparisons, is therefore questionable. There is nothing in [MVC] that contradicts any of the previous papers that have shown clearly a strong relation between seasonal signals obtained from both ground gravity and GRACE satellite data. © The Authors 2014. Published by Oxford University Press on behalf of The Royal Astronomical Society.

Weise A.,Friedrich - Schiller University of Jena | Kroner C.,Physikalisch - Technische Bundesanstalt | Kroner C.,Helmholtz Center Potsdam | Abe M.,Helmholtz Center Potsdam | And 9 more authors.
Journal of Geodynamics | Year: 2012

Time variable gravity field models derived from the satellite mission GRACE have been demonstrated to be consistent with water mass variations in the global hydrological cycle. Independent observations are provided by terrestrial measurements. In order to achieve a maximum of reliability and information gain, ground-based gravity observations may be deployed for comparison with the gravity field variations derived from the GRACE satellite mission. In this context, the data of the network of superconducting gravimeters (SG) of the 'Global Geodynamics Project' (GGP) are of particular interest. This study is focused on the dense SG network in Central Europe with its long-term gravity observations. It is shown that after the separation and reduction of local hydrological effects in the SG observations especially for subsurface stations, the time-variable gravity signals from GRACE agree well with the terrestrial observations from the SG station cluster. Station stability of the SG sites with respect to vertical deformations was checked by GNSS based observations. Most of the variability can be explained by loading effects due to changes in continental water storage, and, in general, the stability of all stations has been confirmed. From comparisons based on correlation and coherence analyses in combination with the root mean square (RMS) variability of the time series emerges, that the maximum correspondence between the SG and GRACE time series is achieved when filtering the GRACE data with Gaussian filters of about 1000. km filter length, which is in accordance with previous publications. Empirical Orthogonal Functions (EOF) analysis was applied to the gravity time series in order to identify common characteristic spatial and temporal patterns. The high correspondence of the first modes for GRACE and SG data implies that the first EOF mode represents a large-scale (Central European) time-variable gravity signal seen by both the GRACE satellites and the SG cluster. © 2011 Elsevier Ltd.

Abe M.,Helmholtz Center Potsdam | Kroner C.,Physikalisch - Technische Bundesanstalt | Forste C.,Helmholtz Center Potsdam | Petrovic S.,Helmholtz Center Potsdam | And 8 more authors.
Geophysical Journal International | Year: 2012

The GRACE (Gravity Recovery and Climate Experiment) satellite mission provides global time-series of the Earth's gravity field. In view of limited resolution and noise from the GRACE data, various filtering techniques have been developed to extract an optimal signal. There is no conclusion on the best filter method so far, however. On the other hand, terrestrial gravity observations from superconducting gravimeters (SGs) provide variations of the gravity field with very high accuracy and time resolution, but only at single points. The aim of this study is to compare GRACE-derived temporal gravity variations with gravity time-series within a network of six Central European SG stations. Empirical orthogonal functions (EOF) analysis was applied to detect common signal characteristics over a 3 yr period (2004-2006). rms Differences between the time-series of several GRACE solutions amount to 60 per cent of the rms variability of the individual data sets. The rms differences between the SG and GRACE time-series are about 70 per cent of the rms value of the SG observations. The best agreement between SG and GRACE is obtained when using a Gaussian filter with filter lengths of 800-1250 km for the GRACE data. With the EOF analysis, a common regional signal can be deduced from all gravity data sets. Nevertheless, differences in the first EOF among the GRACE solutions were up to 40 per cent, and differences of up to 50 per cent were found between the SG-based terrestrial and the GRACE-based satellite observations. © 2012 GFZ German Research Centre for Geosciences Potsdam Geophysical Journal International © 2012 RAS.

Wziontek H.,Federal Agency for Cartography and Geodesy BKG | Wilmes H.,Federal Agency for Cartography and Geodesy BKG | Bonvalot S.,Bureau Gravimetrique International
International Association of Geodesy Symposia | Year: 2012

The steadily growing number of absolute gravimeters and absolute gravity measurements all over the world emphasizes the demand of an overview about existing locations, observations, instruments and institutions involved. As a contribution to the International Gravity Field Service (IGFS), a relational database was designed and implemented in a joint development of BKG and BGI and is in operational status now. Two objectives are aimed at: With freely available meta-data and contact details, the database should give an overview about existing stations and observations, serve as a platform for multidisciplinary cooperation and allow the coordination of forthcoming measurements. Among contributing groups or within international projects, an exchange of gravity values and processing details is possible. The database will function as a data inventory, assuring long term availability of the data. Prospectively, the database will be the foundation for a future international gravity reference system and will serve as a pool for geophysical interpretation of absolute gravity observations on a global scale. © Springer-Verlag Berlin Heidelberg 2012.

Wiatr T.,Federal Agency for Cartography and Geodesy BKG | Suresh G.,Federal Agency for Cartography and Geodesy BKG | Gehrke R.,Federal Agency for Cartography and Geodesy BKG | Hovenbitzer M.,Federal Agency for Cartography and Geodesy BKG
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2016

Copernicus is an European system created for Earth observation and monitoring. It consists of a set of Earth observation satellites and in-situ sensors that provide geo-information that are used, through a set of Copernicus services, for applications related to the environment and global security. The main services of the Copernicus programme address six thematic areas: land, marine, atmosphere, climate change, emergency management and security. In Germany, there is a national service team of Copernicus service coordinators, who are responsible for the national development of the Copernicus services and for providing user-specific information about the Copernicus processes. These coordinators represent the contact points for all the programmes and services concerning their respective Copernicus theme. To publish information about Copernicus, national conferences and workshops are organised. Many people are involved in planning the continuous process of bringing the information to public authorities, research institutes and commercial companies. The Federal Agency for Cartography and Geodesy (Bundesamt für Kartographie und Geodäsie, BKG) is one such organisation, and is mainly responsible for the national land monitoring service of Copernicus. To make use of the freely available data from the Copernicus programme, the Federal Agency for Cartography and Geodesy is currently developing new applications and projects in the field of remote sensing and land monitoring. These projects can be used by other public authorities as examples on how to use the Copernicus data and services for their individual demands and requirements. Copernicus data and services are currently not very commonly used in the daily routine of the national mapping agencies, but they will soon be.

Suresh G.,Federal Agency for Cartography and Geodesy BKG | Gehrke R.,Federal Agency for Cartography and Geodesy BKG | Wiatr T.,Federal Agency for Cartography and Geodesy BKG | Hovenbitzer M.,Federal Agency for Cartography and Geodesy BKG
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2016

Land cover information is essential for urban planning and for land cover change monitoring. This paper presents an overview of the work conducted at the Federal Agency for Cartography and Geodesy (BKG) with respect to Synthetic Aperture Radar (SAR) based land cover classification. Two land cover classification approaches using SAR images are reported in this paper. The first method involves a rule-based classification using only SAR backscatter intensity while the other method involves supervised classification of a polarimetric composite of the same SAR image. The LBM-DE has been used for training and validation of the SAR classification results. Images acquired from the Sentinel-1a satellite are used for classification and the results have been reported and discussed. The availability of Sentinel-1a images that are weather and daylight independent allows for the creation of a land cover classification system that can be updated and validated periodically, and hence, be used to assist other land cover classification systems that use optical data. With the availability of Sentinel-2 data, land cover classification combining Sentinel-1a and Sentinel-2 images present a path for the future.

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