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Jakobsson A.,Development Center | Hopfstock A.,Federal Agency for Cartography and Geodesy BKG | Beare M.,Spatial Group Ltd. | Patrucco R.,Ordnance Survey
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives

This paper will introduce how quality of geo-information can be managed when the production environment is no longer inside one organization (e.g. collection of data is contracted out) or data is compiled from various sources like in case of Spatial Data Infrastructures (SDIs). The bases for quality management of reference geo-information are discussed using three viewpoints; data, process and organization and user centric viewpoints. These viewpoints can be met using ISO 19157 and ISO 19158 standards together with ESDIN developed Quality Model and Data Quality Services Framework (DQSF). Two different services are identified a Data Quality Web Service and a Data User Web Service. We discuss how these principles and services are implemented now within EuroGeographics and Ordnance Survey of Great Britain. Further development will be done during the European Location Framework (ELF) project, which is providing a single source of reference geo-information for Europe during 2013-2016. Source

Wang Q.,Central South University | Wang Q.,Helmholtz Center Potsdam | Xu G.,Helmholtz Center Potsdam | Petrovic S.,Helmholtz Center Potsdam | And 4 more authors.
Advances in Space Research

A regional tropospheric model can be constructed using surveys from GPS ground networks. Using this model the tropospheric delays of a kinematic station within the region can be interpolated. However, such a model is generally not suitable for an airborne platform high above the ground networks. In this paper, a method of constructing a regional tropospheric model for airborne GPS applications is described. First, the kinematic station in the air is projected onto the ground. Then the tropospheric delays at projected point are interpolated from those of the ground networks. Finally, the tropospheric delays at projected point are extended upward to the airborne platform using pressure and temperature gradients and humidity exponential function. For validation of this method, the data of airborne campaign carried out by BKG in cooperation with GFZ and BGR 2008 in the northern Alps are used. The results show that GPS kinematic positioning precision in height component can be improved using this method. © 2011 COSPAR. Published by Elsevier Ltd. All rights reserved. 25. Source

Ojha R.,United States Naval Observatory | Ojha R.,NVI, Inc. | Kadler M.,University of Bamberg | Kadler M.,Erlangen Center for Astroparticle Physics | And 32 more authors.
Astronomy and Astrophysics

Context. A number of theoretical models vie to explain the γ-ray emission from active galactic nuclei (AGN). This was a key discovery of EGRET. With its broader energy coverage, higher resolution, wider field of view and greater sensitivity, the Large Area Telescope (LAT) of the Fermi Gamma-ray Space Telescope is dramatically increasing our knowledge of AGN γ-ray emission. However, discriminating between competing theoretical models requires quasi-simultaneous observations across the electromagnetic spectrum. By resolving the powerful parsec-scale relativistic outflows in extragalactic jets and thereby allowing us to measure critical physical properties, Very Long Baseline Interferometry observations are crucial to understanding the physics of extragalactic γ-ray objects. Aims. We introduce the TANAMI program (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry) which is monitoring an initial sample of 43 extragalactic jets located south of-30 degrees declination at 8.4 GHz and 22 GHz since 2007. All aspects of the program are discussed. First epoch results at 8.4 GHz are presented along with physical parameters derived therefrom. Methods. These observations were made during 2007/2008 using the telescopes of the Australian Long Baseline Array in conjunction with Hartebeesthoek in South Africa. These data were correlated at the Swinburne University correlator. Results. We present first epoch images for 43 sources, some observed for the first time at milliarcsecond resolution. Parameters of these images as well as physical parameters derived from them are also presented and discussed. These and subsequent images from the TANAMI survey are available at http://pulsar.sternwarte.uni-erlangen.de/tanami/. Conclusions. We obtain reliable, high dynamic range images of the southern hemisphere AGN. All the quasars and BL Lac objects in the sample have a single-sided radio morphology. Galaxies are either double-sided, single-sided or irregular. About 28% of the TANAMI sample has been detected by LAT during its first three months of operations. Initial analysis suggests that when galaxies are excluded, sources detected by LAT have larger opening angles than those not detected by LAT. Brightness temperatures of LAT detections and non-detections seem to have similar distributions. The redshift distributions of the TANAMI sample and sub-samples are similar to those seen for the bright γ-ray AGN seen by LAT and EGRET but none of the sources with a redshift above 1.8 have been detected by LAT. © 2010 ESO. Source

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

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. Source

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

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. Source

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