References of "Sidorov, Dmitry 50003088"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailThe King Edward Point Geodetic Observatory, South Georgia, South Atlantic Ocean: A First Evaluation and Potential Contributions to Geosciences
Teferle, Felix Norman UL; Hunegnaw, Addisu UL; Ahmed, Furqan UL et al

in Willis, Pascal; Rizos, Chris (Eds.) IAG 150 Years Proceedings of the 2013 IAG Scientific Assembly, Postdam, Germany, 1–6 September, 2013 (2016)

During February 2013 the King Edward Point (KEP) Geodetic Observatory was established in South Georgia, South Atlantic Ocean, through a University of Luxembourg funded research project and in ... [more ▼]

During February 2013 the King Edward Point (KEP) Geodetic Observatory was established in South Georgia, South Atlantic Ocean, through a University of Luxembourg funded research project and in collaboration with the United Kingdom National Oceanography Centre, British Antarctic Survey, and Unavco, Inc. Due to its remote location in the South Atlantic Ocean, as well as being one of few subaerial exposures of the Scotia tectonic plate, South Georgia Island has been a key location for a number of global monitoring networks, e.g. seismic, geomagnetic and oceanic. However, no permanent geodetic monitoring station has been established previously, despite the lack of observations from this region. In this study we will present an evaluation of the GNSS and meteorological observations from the KEP Geodetic Observatory for the period from 14 February to 31 December 2013. We calculate multipath and positioning statistics and compare these to those from IGS stations using equipment of the same type. The on-site meteorological data are compared to those from the nearby KEP meteorological station and the NCEP/NCAR reanalysis model, and the impact of these data sets on integrated water vapour estimates is evaluated. We discuss the installation in terms of its potential contributions to sea level observations using tide gauges and satellite altimetry, studies of tectonics, glacio-isostatic adjustment and atmospheric processes. [less ▲]

Detailed reference viewed: 254 (41 UL)
Full Text
Peer Reviewed
See detailImpact of Antenna Phase Centre Calibrations on Position Time Series: Preliminary Results
Sidorov, Dmitry UL; Teferle, Felix Norman UL

in Willis, Pascal; Rizos, Chris (Eds.) IAG 150 Years Proceedings of the 2013 IAG Scientific Assembly, Postdam,Germany, 1–6 September, 2013 (2016)

Advances in GPS error modelling and the continued effort of re-processing have considerably decreased the scatter in position estimates over the last decade. The associated reduction of noise in derived ... [more ▼]

Advances in GPS error modelling and the continued effort of re-processing have considerably decreased the scatter in position estimates over the last decade. The associated reduction of noise in derived position time series has revealed the presence of previously undetected periodic signals. It has been shown that these signals have frequencies related to the orbits of the GPS satellites. A number of potential sources for these periodicities at the draconitic frequency and its harmonics have already been suggested in the literature and include, e.g., errors in the sub-daily tidal models, multipath and unresolved integer ambiguities. Due to the geometrical relationship between the observing site and the orbiting satellite, deficiencies in the modelling of electromagnetic phase centres of receiving antennas have the potential to also contribute to the discovered periodic signals. The change from relative to absolute type mean antenna/radome calibrations within the International GNSS Service (IGS) led to a significant improvement, but the use of individual calibrations could possibly add further refinements to computed solutions. However, at this stage providing individual calibrations for all IGS stations is not feasible. Furthermore, antenna near-field electromagnetic effects might outweigh the benefits of individual calibrations once an antenna is permanently installed. In this study, we investigate the differences between position estimates obtained using individual and type mean antenna/radome calibrations as used by the IGS community. We employ position time series derived from precise point positioning (PPP) as implemented in two scientific GNSS software packages. Our results suggest that the calibration differences propagate directly into the position estimates, affecting both sub-daily and daily results and yielding periodic variations. The sub-daily variations have periods close to half a sidereal day and one sidereal day with peak-to-peak amplitudes of up to 10~mm in all position components. The stacked power spectra of the daily difference time series reveal peaks at the GPS draconitic frequency and its harmonics with peak-to-peak amplitudes of up to 1~mm. Although these results are still preliminary, they confirm that small differences between individual and type mean antenna/radome calibrations propagate into position time series and may be partly responsible for the spurious signals with draconitic frequency and its harmonics. [less ▲]

Detailed reference viewed: 192 (31 UL)
Full Text
See detailSofia University GNSS Analysis Center (SUGAC)
Simeonov, Tzvetan; Sidorov, Dmitry UL; Teferle, Felix Norman UL et al

Scientific Conference (2015, May 20)

The Sofia University GNSS Analysis Centre (SUGAC, suada.phys.uni-sofia.bg) is a new analysis centre established via collaboration between the Department of Meteorology and Geophysics of Sofia University ... [more ▼]

The Sofia University GNSS Analysis Centre (SUGAC, suada.phys.uni-sofia.bg) is a new analysis centre established via collaboration between the Department of Meteorology and Geophysics of Sofia University, the IPOS - BuliPOS GNSS network in Bulgaria, the University of Luxembourg and the Space Research and Technology Institute at the Bulgarian Academy of Sciences. In April 2014, the first processing campaign took place. One year of GNSS data from 7 stations of the BuliPOS network were processed in collaboration with the University of Luxembourg. Tropospheric products (Zenith Total Delay and gradients) with 5 min temporal resolution were obtained using the NAPEOS software, developed by ESA. The tropospheric products from this campaign were then used for validation of the Weather Research and Forecasting (WRF) model as well as for case studies during intense precipitation events and fog. In this work the WRF model validation for Bulgaria will be presented. Future work will be the establishment of autonomous near real- time processing of the regional ground-based GNSS network in Southeast Europe in support of the EUMETNET E-GVAP and COST ES1206 ”Advanced Global Navigation Satellite Systems for Severe Weather Events and Climate” projects. [less ▲]

Detailed reference viewed: 86 (3 UL)
Full Text
See detailReceiver Antenna and Empirical Multipath Correction Models for GNSS Solutions
Sidorov, Dmitry UL

Doctoral thesis (2015)

The advent of the Global Navigation Satellite Systems (GNSSs), in particular, the U.S. Global Positioning System (GPS) and the Russia's GLObalnaya NAvigatsionnaya Sputnikovaya Sistema (GLONASS) have ... [more ▼]

The advent of the Global Navigation Satellite Systems (GNSSs), in particular, the U.S. Global Positioning System (GPS) and the Russia's GLObalnaya NAvigatsionnaya Sputnikovaya Sistema (GLONASS) have revolutionized geodesy by enabling a cheap and robust way of providing precise and continuous position estimates to users. Moreover, GNSSs have been shown to be extremely useful for a wide variety of other applications, in particular, geophysical, atmospheric, oceanographic studies, as well as industrial applications. Although the last two decades of GNSS exploitation were marked by great advances in accuracy and precision of the involved techniques, improvements can still be made. This thesis addresses the topic of receiver antenna and empirical multipath correction models, aiming to further improve GNSS solutions. GNSS utilizes measurement of ranges between satellites orbiting the Earth and receivers located on the Earth's surface through modulated electromagnetic signals. However, the actual point where the signal is received and which is denoted as a phase centre of an antenna, is not fixed, but varies depending on many parameters. Therefore, high-precision GNSS fundamentally depends on antenna phase centre corrections (PCC) and failing to accurately apply the latter results in biases and elevated uncertainties of estimated GNSS solutions. Additionally, due to repeating satellite-receiver geometry, these phase centre modelling deficiencies may lead to the generation of harmonic signals in the time series of the estimated parameters. In turn, identifying geophysical signals in the time series may be compromised by the presence of these artificial signals, resulting in inaccuracies in derived models. The geodetic community employs averaged (type-mean) PCC to estimate GNSS orbits, clock biases, tropospheric delays and other parameters, as well as to realize and provide access to the terrestrial reference frame. However, the use of individual PCC is beneficial for GNSS solutions, as it allows for more accurate estimation of satellite orbits and ground station coordinates. The latter is demonstrated using a regional network of 55 GNSS stations and processing the GPS data over a period of 10 years. Another topic addressed in this thesis concerns development of empirical site models (ESMs) using post-fit phase residuals accumulated over a period of time. These models are aimed to mitigate multipath and other unmodelled site effects that have a negative impact on GNSS solutions. Using a global network of stations the derived ESMs are evaluated for their capability to improve the GPS orbit determination as well as to increase the accuracy of ground station coordinate estimation. [less ▲]

Detailed reference viewed: 136 (18 UL)
Full Text
See detailImpact of Station GNSS Antenna Phase Centre Calibrations on Satellite Orbits and Station Coordinates: Preliminary Results
Sidorov, Dmitry UL; Teferle, Felix Norman UL

Poster (2014, October 14)

The electromagnetic phase centre of a Global Navigation Satellite System (GNSS) antenna does not coincide with the physical one and depends on the azimuth and elevation of the incoming signals. To improve ... [more ▼]

The electromagnetic phase centre of a Global Navigation Satellite System (GNSS) antenna does not coincide with the physical one and depends on the azimuth and elevation of the incoming signals. To improve processing results, the International GNSS Service has developed antenna phase centre corrections (PCC), which include models for constant and variable biases, i.e. phase centre offsets and phase centre variations. By assuming that the small differences in PCCs between antenna/radome combinations of the same type/model are negligible, so called type-mean PCCs have been generated and, for practical reasons, have been widely applied. The type-mean PCCs are averaged corrections, which are composed from several individual PCCs. Contrary to the general assumption, individual PCCs may sometimes be significantly different for antennas of the same type and it can be argued, that the use of type-mean instead of individual calibrations may degrade GNSS-derived products, such as satellite orbits and station coordinates. Furthermore, through simple geometric considerations it can be shown that inaccuracies in the PCCs may propagate into time series of GNSS solutions and may contribute some power at the orbital frequencies and their harmonics. In this study we assess the impact of the applied antenna PCCs on satellite orbits and station coordinates. As the availability of individual PCCs for GNSS stations is very limited, we analyzed a global network with stations mainly located in Europe. We used 10 years of GPS data in our processing. Despite the limitations imposed by the poor network geometry, we observed improvements in orbit overlaps at day boundaries when individual antenna PCCs were used compared to the respective type-mean solutions. Additionally, we analyzed the impact of the applied PCCs on Precise Point Positioning (PPP) station coordinates using our computed orbits. Our preliminary results showed that out of two PPP runs, the one with individual PCCs and respective orbit set reduced the noise in solutions compared to the other PPP run. We conclude that the use of individual PCCs is advantageous for derived GNSS products, as improvements are observed both in the estimated satellite orbits and station coordinate time series. [less ▲]

Detailed reference viewed: 91 (22 UL)
Full Text
See detailSUGAC: Sofia University GNSS Analysis Center
Simeonov, Tzvetan; Sidorov, Dmitry UL; Teferle, Felix Norman UL et al

Poster (2014, June 25)

The Sofia University GNSS Analysis Centre (SUGAC, suada.phys.uni-sofia.bg) is a new analysis centre established via collaboration between the Department of Meteorology and Geophysics of Sofia University ... [more ▼]

The Sofia University GNSS Analysis Centre (SUGAC, suada.phys.uni-sofia.bg) is a new analysis centre established via collaboration between the Department of Meteorology and Geophysics of Sofia University, the IPOS - BuliPOS GNSS network in Bulgaria and the University of Luxembourg. In April 2014, the first processing campaign took place. One year GNSS data from 7 stations of the BuliPOS network are processed in collaboration with the University of Luxembourg. Tropospheric products (Zenith Total Delay and gradients) with 5 min temporal resolution are obtained using the NAPEOS software, developed by ESA. The tropospheric products from this campaign will be used for validation of the Weather Research and Forecasting (WRF) model as well as for case studies during intense precipitation events and fog. In this work the WRF model validation for Bulgaria will be presented. Future work will be the establishment of autonomous near real-time processing of the regional ground-based GNSS network in Southeast Europe in support of the EUMETNET E-GVAP and COST ES1206 ”Advanced Global Navigation Satellite Systems for Severe Weather Events and Climate” projects. [less ▲]

Detailed reference viewed: 102 (0 UL)
Full Text
See detailPotential Contributions to Geoscience from GNSS Observations of the King Edward Point Geodetic Observatory, South Georgia, South Atlantic Ocean
Teferle, Felix Norman UL; Hunegnaw, Addisu UL; Ahmed, Furqan UL et al

Poster (2013, September 01)

During February 2013 the King Edward Point (KEP) Geodetic Observatory was established in South Georgia, South Atlantic Ocean, through a University of Luxembourg funded research project and in ... [more ▼]

During February 2013 the King Edward Point (KEP) Geodetic Observatory was established in South Georgia, South Atlantic Ocean, through a University of Luxembourg funded research project and in collaboration with the United Kingdom’s National Oceanography Centre, British Antarctic Survey and Unavco, Inc. Due to its remote location in the South Atlantic Ocean, as well as, being one of few subaerial exposures of the Scotia plate, South Georgia Island has been a key location for a number of global monitoring networks, e.g. seismic, geomagnetic and oceanic. However, no geodetic monitoring station has been established, e.g. by the International Global Navigation Satellite System (GNSS) Service (IGS) community, despite the lack of such observations from this region. In this study we will present an evaluation of the GNSS observations from the KEP Geodetic Observatory for the period from February to August 2013. We calculate multipath and positioning statistics and compare these to those from IGS stations. The on-site meteorological data is compared to those from the nearby KEP meteorological station and global numerical weather models, and the impact of these data sets on delay and integrated water vapour estimates will be evaluated. We will discuss the installation in terms of its potential contributions to sea level observations using tide gauges and satellite altimetry, studies of tectonics, glacio-isostatic adjustment and atmospheric processes. [less ▲]

Detailed reference viewed: 93 (14 UL)
Full Text
See detailAntenna phase centre calibration effects on position time-series: preliminary results
Sidorov, Dmitry UL; Teferle, Felix Norman UL

Poster (2013, September 01)

Advances in GPS error modelling and the continued effort of re-processing have considerably decreased the scatter in position estimates over the last two decades. The associated reduction of noise in ... [more ▼]

Advances in GPS error modelling and the continued effort of re-processing have considerably decreased the scatter in position estimates over the last two decades. The associated reduction of noise in derived position time-series has revealed the presence of previously undetected periodic signals. It has been shown that these signals have frequencies related to the orbits of GPS satellites. A number of potential sources for these periodicities at the draconitic frequency and its harmonics have already been suggested in the literature and include, e.g. errors in the sub-daily tidal models, multipath and unresolved integer ambiguities. Due to the geometrical relationship between an observation point and an orbiting satellite, deficiencies in the modelling of electromagnetic phase centres of receiving antennas have the potential to also contribute to the discovered periodic signals. The change from relative to absolute type mean antenna/radome calibrations within the international GNSS service (IGS) lead to a significant improvement and the use of individual calibrations could add further refinements to computed solutions. However, at this stage providing individual calibrations for all IGS stations is not feasible. Furthermore, antenna near-field electromagnetic effects might out-weight the benefits of individual calibrations once an antenna is permanently installed. In this study we investigate the differences between position estimates obtained using individual and type mean antenna/radome calibrations as used by the IGS community. We employ position time-series derived from precise point positioning (PPP) as implemented in two scientific GNSS software packages. Our results suggest that the differences in the employed calibrations propagate directly into the position estimates, affecting both sub-daily and daily results and yielding periodic variations. The sub-daily variations have periods close to half a sidereal day and one sidereal day with amplitudes of up to 10 mm in all position components. The stacked power spectra of the daily difference time-series reveal peaks at the GPS draconitic frequency and its harmonics, having the associated amplitudes of up to 1 mm. Although these results are still preliminary, they confirm that small differences between individual and type mean antenna/radome calibrations propagate into position time series and may be partly responsible for the spurious signals with draconitic frequency and its harmonics. [less ▲]

Detailed reference viewed: 123 (22 UL)