Inst. Geodäsie und Geoinformationstechnik

119 Items

Recent Submissions
Derivation and analysis of hydrological parameters from ground-based GNSS stations

Simeonov Simeonov, Tzvetan (2021)

The ability to measure multiple environmental parameters, such as atmospheric water vapour, soil moisture and snow height with the same hardware is the main advantage of Global Navigation Satellite System (GNSS) environmental measurements over other observation techniques. In this thesis state-of-art ground-based GNSS methods for environmental monitoring are used to derive atmospheric water vap...

Refining ionospheric delay modeling for undifferenced and uncombined GNSS data processing

Zhao, Qile ; Wang, YinTong ; Gu, Shengfeng ; Zheng, Fu ; Shi, Chuang ; Ge, Maorong ; Schuh, Harald (2018-07-31)

To access the full capabilities of multi-frequency signals from the modernized GPS, GLONASS and newly deployed BDS, Galileo, the undifferenced and uncombined observable model in which the individual signal of each frequency is treated as independent observable has drawn increasing interest in GNSS community. The ionosphere delay is the major issue in the undifferenced and uncombined observable ...

Multi-GNSS satellite clock estimation constrained with oscillator noise model in the existence of data discontinuity

Shi, Chuang ; Guo, Shiwei ; Shengfeng, Gu ; Yang, Xinhao ; Gong, Xiaopeng ; Deng, Zhiguo ; Ge, Maorong ; Schuh, Harald (2018-07-25)

During the past years, real-time precise point positioning has been proven to be an efficient tool in the applications of navigation, precise orbit determination of LEO as well as earthquake and tsunami early warning, etc. One of the most crucial issues of these applications is the high-precision real-time GNSS satellite clock. Though the performance and character of the GNSS onboard atomic fre...

Performance Evaluation of VTEC GIMs for Regional Applications during Different Solar Activity Periods, Using RING TEC Values

Tornatore, Vincenza ; Cesaroni, Claudio ; Pezzopane, Michael ; Alizadeh, Mohamad Mahdi ; Schuh, Harald (2021-04-10)

This paper presents a comparison of the vertical total electron content (vTEC) estimated over Italy using two different approaches: the GPS Global Ionosphere Maps (GIMs) and the so-called “calibration technique” developed by Ciraolo in 2007. The study has been carried out at a regional level by considering three Italian dual-frequency stations of the GPS permanent network “Rete Integrata Nazion...

Observable quality assessment of broadband very long baseline interferometry system

Xu, Ming H. ; Anderson, James M. ; Heinkelmann, Robert ; Lunz, Susanne ; Schuh, Harald ; Wang, Guangli (2021-04-12)

The next-generation, broadband geodetic very long baseline interferometry system, named VGOS, is developing its global network, and VGOS networks with a small size of 3–7 stations have already made broadband observations from 2017 to 2019. We made quality assessments for two kinds of observables in the 21 VGOS sessions currently available: group delay and differential total electron content (δT...

Improving the modeling of the atmospheric delay in the data analysis of the Intensive VLBI sessions and the impact on the UT1 estimates

Nilsson, Tobias ; Soja, Benedikt ; Balidakis, Kyriakos ; Karbon, Maria ; Heinkelmann, Robert ; Deng, Zhiguo ; Schuh, Harald (2017-01-11)

The very long baseline interferometry (VLBI) Intensive sessions are typically 1-h and single-baseline VLBI sessions, specifically designed to yield low-latency estimates of UT1-UTC. In this work, we investigate what accuracy is obtained from these sessions and how it can be improved. In particular, we study the modeling of the troposphere in the data analysis. The impact of including external i...

Correcting surface loading at the observation level: impact on global GNSS and VLBI station networks

Männel, Benjamin ; Dobslaw, Henryk ; Dill, Robert ; Glaser, Susanne ; Balidakis, Kyriakos ; Thomas, Maik ; Schuh, Harald (2019-09-26)

Time-dependent mass variations of the near-surface geophysical fluids in atmosphere, oceans and the continental hydrosphere lead to systematic and significant load-induced deformations of the Earth’s crust. The Earth System Modeling group of Deutsches GeoForschungsZentrum (ESMGFZ) provides vertical and horizontal surface deformations based on numerical models of the global geophysical fluids in...

Sea-ice concentration derived from GNSS reflection measurements in Fram Strait

Semmling, A. Maximilian ; Rösel, Anja ; Divine, Dmitry V. ; Gerland, Sebastian ; Stienne, Georges ; Rebul, Serge ; Ludwig, Marcel ; Wickert, Jens ; Schuh, Harald (2019-09-05)

Reflection power derived from the global navigation satellite system (GNSS) observations and its sensitivity to sea-ice concentration are investigated in this article. A corresponding experiment has been conducted during the Fram Strait cruise of the Norwegian research vessel Lance in summer 2016. The dedicated setup with a GNSS Occultation Reflectometry Scatterometry (GORS) receiver and dual-p...

Integrated processing of ground- and space-based GPS observations: improving GPS satellite orbits observed with sparse ground networks

Huang, Wen ; Männel, Benjamin ; Sakic, Pierre ; Ge, Maorong ; Schuh, Harald (2020-10-10)

The precise orbit determination (POD) of Global Navigation Satellite System (GNSS) satellites and low Earth orbiters (LEOs) are usually performed independently. It is a potential way to improve the GNSS orbits by integrating LEOs onboard observations into the processing, especially for the developing GNSS, e.g., Galileo with a sparse sensor station network and Beidou with a regional distributed...

Use of the East Asia GPS receiving network to observe ionospheric VTEC variations, scintillation and EIA features during the Solar Cycle 24

Nguyen, Thai Chinh (2021)

The ionosphere is a complex and highly variable physical system with the F-layer, which occupies at the highest altitude, contains the greatest concentration of free electrons. Under the extreme circumstance of the ionosphere such as in the periods of high solar activity or magnetic storms or simply in the equinoctial months each year, this layer is very often disturbed. During the disturbances...

An improved empirical harmonic model of the celestial intermediate pole offsets from a global VLBI solution

Belda, Santiago ; Heinkelmann, Robert ; Ferrándiz, José M. ; Karbon, Maria ; Nilsson, Tobias ; Schuh, Harald (2017-09-28)

Very Long Baseline Interferometry (VLBI) is the only space geodetic technique capable of measuring all the Earth orientation parameters (EOP) accurately and simultaneously. Modeling the Earth's rotational motion in space within the stringent consistency goals of the Global Geodetic Observing System (GGOS) makes VLBI observations essential for constraining the rotation theories. However, the ina...

Earth orientation parameters from VLBI determined with a Kalman filter

Karbon, Maria ; Soja, Benedikt ; Nilsson, Tobias ; Deng, Zhiguo ; Heinkelmann, Robert ; Schuh, Harald (2017-09-06)

This paper introduces the reader to our Kalman filter developed for geodetic VLBI (very long baseline interferometry) data analysis. The focus lies on the EOP (Earth Orientation Parameter) determination based on the Continuous VLBI Campaign 2014 (CONT14) data, but also earlier CONT campaigns are analyzed. For validation and comparison purposes we use EOP determined with the classical LSM (least...

Impact of different NWM-derived mapping functions on VLBI and GPS analysis

Nikolaidou, Thalia ; Balidakis, Kyriakos ; Nievinski, Felipe ; Santos, Marcelo ; Schuh, Harald (2018-06-11)

In recent years, numerical weather models have shown the potential to provide a good representation of the electrically neutral atmosphere. This fact has been exploited for the modeling of space geodetic observations. The Vienna Mapping Functions 1 (VMF1) are the NWM-based model recommended by the latest IERS Conventions. The VMF1 are being produced 6 hourly based on the European Centre for Med...

Polar motion prediction using the combination of SSA and Copula-based analysis

Modiri, Sadegh ; Belda, Santiago ; Heinkelmann, Robert ; Hoseini, Mostafa ; Ferrándiz, José M. ; Schuh, Harald (2018-07-11)

The real-time estimation of polar motion (PM) is needed for the navigation of Earth satellite and interplanetary spacecraft. However, it is impossible to have real-time information due to the complexity of the measurement model and data processing. Various prediction methods have been developed. However, the accuracy of PM prediction is still not satisfactory even for a few days in the future. ...

Global morphology of ionospheric sporadic E layer from the FormoSat-3/COSMIC GPS radio occultation experiment

Tsai, Lung-Chih ; Su, Shin-Yi ; Liu, Chao-Han ; Schuh, Harald ; Wickert, Jens ; Alizadeh, Mohamad Mahdi (2018-09-12)

Ionospheric sporadic-E (Es) activity and global morphology were studied using the 50 Hz signal-to-noise ratio amplitude and excess phase measurements from the FormoSat-3/Constellation Observing System for Meteorology, Ionosphere and Climate (FS3/COSMIC) GPS radio occultation (RO) observations. The results are presented for data collected during the last sunspot cycle from mid-2006 to the end of...

ICGEM – 15 years of successful collection and distribution of global gravitational models, associated services, and future plans

Ince, E. Sinem ; Barthelmes, Franz ; Reißland, Sven ; Elger, Kirsten ; Förste, Christoph ; Flechtner, Frank ; Schuh, Harald (2019-05-15)

The International Centre for Global Earth Models (ICGEM, http://icgem.gfz-potsdam.de/, last access: 6 May 2019) hosted at the GFZ German Research Centre for Geosciences (GFZ) is one of the five services coordinated by the International Gravity Field Service (IGFS) of the International Association of Geodesy (IAG). The goal of the ICGEM service is to provide the scientific community with a state...

A new hybrid method to improve the ultra-short-term prediction of LOD

Modiri, Sadegh ; Belda, Santiago ; Hoseini, Mostafa ; Heinkelmann, Robert ; Ferrándiz, José M. ; Schuh, Harald (2020-02-05)

Accurate, short-term predictions of Earth orientation parameters (EOP) are needed for many real-time applications including precise tracking and navigation of interplanetary spacecraft, climate forecasting, and disaster prevention. Out of the EOP, the LOD (length of day), which represents the changes in the Earth’s rotation rate, is the most challenging to predict since it is largely affected b...

Improving Low Earth Orbit (LEO) prediction with accelerometer data

Ge, Haibo ; Li, Bofeng ; Ge, Maorong ; Nie, Liangwei ; Schuh, Harald (2020-05-17)

Low Earth Orbit (LEO) satellites have been widely used in scientific fields or commercial applications in recent decades. The demands of the real time scientific research or real time applications require real time precise LEO orbits. Usually, the predicted orbit is one of the solutions for real time users, so it is of great importance to investigate LEO orbit prediction for users who need real...

Occurrence climatology of equatorial plasma bubbles derived using FormoSat-3 ∕ COSMIC GPS radio occultation data

Kepkar, Ankur ; Arras, Christina ; Wickert, Jens ; Schuh, Harald ; Alizadeh, Mahdi ; Tsai, Lung-Chih (2020-05-13)

The Global Positioning System – Radio Occultation (GPS-RO) observations from FormoSat-3 ∕ COSMIC are used to comprehend the global distribution of equatorial plasma bubbles which are characterized by depletion regions of plasma in the F region of the ionosphere. Plasma bubbles that cause intense scintillation of the radio signals are identified based on the S4 index derived from the 1 Hz raw si...

GPS + Galileo + BeiDou precise point positioning with triple-frequency ambiguity resolution

Li, Pan ; Jiang, Xinyuan ; Zhang, Xiaohong ; Ge, Maorong ; Schuh, Harald (2020-05-27)

Along with the rapid development of GNSS, not only BeiDou, but also Galileo, and the newly launched GPS satellites can provide signals on three frequencies at present. To fully take advantage of the multi-frequency multi-system GNSS observations on precise point positioning (PPP) technology, this study aims to implement the triple-frequency ambiguity resolution (AR) for GPS, Galileo, and BeiDou...