Inst. Geodäsie und Geoinformationstechnik

70 Items

Recent Submissions
First evidence of mesoscale ocean eddies signature in GNSS reflectometry measurements

Hoseini, Mostafa ; Asgarimehr, Milad ; Zavorotny, Valery ; Nahavandchi, Hossein ; Ruf, Chris ; Wickert, Jens (2020-02-06)

Feasibility of sensing mesoscale ocean eddies using spaceborne Global Navigation Satellite Systems-Reflectometry (GNSS-R) measurements is demonstrated for the first time. Measurements of Cyclone GNSS (CYGNSS) satellite missions over the eddies, documented in the Aviso eddy trajectory atlas, are studied. The investigation reports on the evidence of normalized bistatic radar cross section ( σ0 ) ...

New nonlinear adjustment approaches for applications in geodesy and related fields

Malissiovas, Georgios (2019)

This dissertation deals with a class of nonlinear adjustment problems that has a direct least squares solution for certain weighting cases. In the literature of mathematical statistics these problems are expressed in a nonlinear model called Errors-In-Variables (EIV) and their solution became popular as total least squares (TLS). The TLS solution is direct and involves the use of singular value...

Multi-GNSS precise position, velocity, and acceleration determination for airborne gravimetry over Antarctica

Min, Li (2020)

The precise knowledge of aircraft position, velocity, and acceleration is a mandatory prerequisite for airborne gravimetry. For the determination of these quantities the Global Navigation Satellite System (GNSS) plays an important role. However, kinematic positioning over Antarctica is a challenging task which is different from positioning in low-latitude regions. The main reason is the sparse ...

Retrieving Precipitable Water Vapor From Shipborne Multi‐GNSS Observations

Wang, Jungang ; Wu, Zhilu ; Semmling, Maximilian ; Zus, Florian ; Gerland, Sebastian ; Ramatschi, Markus ; Ge, Maorong ; Wickert, Jens ; Schuh, Harald (2019-05-15)

Precipitable water vapor (PWV) is an important parameter for climate research and a crucial factor to achieve high accuracy in satellite geodesy and satellite altimetry. Currently Global Navigation Satellite System (GNSS) PWV retrieval using static Precise Point Positioning is limited to ground stations. We demonstrated the PWV retrieval using kinematic Precise Point Positioning method with shi...

Coordinates and maps of the Apollo 17 landing site

Haase, Isabel ; Wählisch, Marita ; Gläser, Philipp ; Oberst, Jürgen ; Robinson, Mark S. (2018-12-07)

We carried out an extensive cartographic analysis of the Apollo 17 landing site and determined and mapped positions of the astronauts, their equipment, and lunar landmarks with accuracies of better than ±1 m in most cases. To determine coordinates in a lunar body‐fixed coordinate frame, we applied least squares (2‐D) network adjustments to angular measurements made in astronaut imagery (Hasselb...

Can GNSS reflectometry detect precipitation over oceans?

Asgarimehr, Milad ; Zavorotny, Valery ; Wickert, Jens ; Reich, Sebastian (2018-11-06)

For the first time, a rain signature in Global Navigation Satellite System Reflectometry (GNSS‐R) observations is demonstrated. Based on the argument that the forward quasi‐specular scattering relies upon surface gravity waves with lengths larger than several wavelengths of the reflected signal, a commonly made conclusion is that the scatterometric GNSS‐R measurements are not sensitive to the s...

Estimating integrated water vapor trends from VLBI, GPS,and numerical weather models: sensitivity totropospheric parameterization

Balidakis, Kyriakos ; Nilsson, Tobias ; Zus, Florian ; Glaser, Susanne ; Heinkelmann, Robert ; Deng, Zhiguo ; Schuh, Harald (2018-06-20)

In this study, we estimate integrated water vapor (IWV) trends from very long baseline interferometry (VLBI) and global navigation satellite systems (GNSS) data analysis, as well as from numerical weather models (NWMs). We study the impact of modeling and parameterization of the tropospheric delay from VLBI on IWV trends. We address the impact of the meteorological data source utilized to model...

A Decentralized Processing Schema for Efficient and Robust Real-time Multi-GNSS Satellite Clock Estimation

Jiang, Xinyuan ; Gu, Shengfeng ; Li, Pan ; Ge, Maorong ; Schuh, Harald (2019-11-05)

Real-time multi-GNSS precise point positioning (PPP) requires the support of high-rate satellite clock corrections. Due to the large number of ambiguity parameters, it is difficult to update clocks at high frequency in real-time for a large reference network. With the increasing number of satellites of multi-GNSS constellations and the number of stations, real-time high-rate clock estimation be...

The GFZ GRACE RL06 Monthly Gravity Field Time Series: Processing Details and Quality Assessment

Dahle, Christoph ; Murböck, Michael ; Flechtner, Frank ; Dobslaw, Henryk ; Michalak, Grzegorz ; Neumayer, Karl Hans ; Abrykosov, Oleh ; Reinhold, Anton ; König, Rolf ; Sulzbach, Roman ; Förste, Christoph (2019-09-11)

Time-variable gravity field models derived from observations of the Gravity Recovery and Climate Experiment (GRACE) mission, whose science operations phase ended in June 2017 after more than 15 years, enabled a multitude of studies of Earth’s surface mass transport processes and climate change. The German Research Centre for Geosciences (GFZ), routinely processing such monthly gravity fields as...

Mitigation of Unmodeled Error to Improve the Accuracy of Multi-GNSS PPP for Crustal Deformation Monitoring

Zheng, Kai ; Zhang, Xiaohong ; Li, Xingxing ; Li, Pan ; Chang, Xiao ; Sang, Jizhang ; Ge, Maorong ; Schuh, Harald (2019-09-25)

High-rate multi-constellation global navigation satellite system (GNSS) precise point positioning (PPP) has been recognized as an efficient and reliable technique for large earthquake monitoring. However, the displacements derived from PPP are often overwhelmed by the centimeter-level noise, therefore they are usually unable to detect slight deformations which could provide new findings for geo...

On the development and impact of propagation delay and geophysical loading on space geodetic technique data analysis

Balidakis, Kyriakos (2019)

This study contributes to the effort of space geodesy to reach the 1 mm accuracy level on a global scale. This stringent requirement is vital to realize a global reference system upon which phenomena such as sea-level rise can be reliably monitored. The study deals with two interrelated challenges: modeling geophysical loads imposed on the crust of the Earth and quantifying the atmospheric prop...

Observations of meteors in the Earth’s atmosphere: Reducing data from dedicated double-station wide-angle cameras

Margonis, Anastasios ; Christou, Apostolos ; Oberst, Jürgen (2018-10-17)

Meteoroids entering the Earth’s atmosphere can be observed as meteors, thereby providing useful information on their formation and hence on their parent bodies. We developed a data reduction software package for double station meteor data from the SPOSH camera, which includes event detection, image geometric and radiometric calibration, radiant and speed estimates, trajectory and orbit determin...

Characterisation of the Perseid meteoroid stream through SPOSH observations between 2010–2016

Margonis, Anastasios ; Christou, Apostolos ; Oberst, Jürgen (2019-06-07)

We have characterised the Perseid meteoroid stream from data acquired in a series of observing campaigns between 2010 and 2016. The data presented in this work were obtained by the Smart Panoramic Optical Sensor Head (SPOSH), an all-sky camera system designed to image faint transient noctilucent phenomena on dark planetary hemispheres. For the data reduction, a sophisticated software package wa...

Using Convective Available Potential Energy (CAPE) and Dew-Point Temperature to Characterize Rainfall-Extreme Events in the South-Central Andes

Ramezani Ziarani, Maryam ; Bookhagen, Bodo ; Schmidt, Torsten ; Wickert, Jens ; de la Torre, Alejandro ; Hierro, Rodrigo (2019-07-08)

The interactions between atmosphere and steep topography in the eastern south–central Andes result in complex relations with inhomogenous rainfall distributions. The atmospheric conditions leading to deep convection and extreme rainfall and their spatial patterns—both at the valley and mountain-belt scales—are not well understood. In this study, we aim to identify the dominant atmospheric condi...

The measurement- and model-based structural analysis for damage detection

Wu, Cheng-Chieh (2019)

The present work is intended to make a contribution to the monitoring of civil engineering structures. The detection of damage to structures is based on the evaluation of spatially and temporally distributed hybrid measurements. The acquired data can be evaluated purely geometrically or physically. It is preferable to do the latter, since the cause of damage can be determined by means of geomet...

Re-evaluation of Apollo 17 Lunar Seismic Profiling Experiment data

Heffels, Alexandra ; Knapmeyer, Martin ; Oberst, Jürgen ; Haase, Isabel (2016-12-10)

We re-analyzed Apollo 17 Lunar Seismic Profiling Experiment (LSPE) data to improve our knowledge of the subsurface structure of this landing site. We use new geometrically accurate 3-D positions of the seismic equipment deployed by the astronauts, which were previously derived using high-resolution images by Lunar Reconnaissance Orbiter (LRO) in combination with Apollo astronaut photography. Th...

Sea Ice Detection Based on Differential Delay-Doppler Maps from UK TechDemoSat-1

Zhu, Yongchao ; Yu, Kegen ; Zou, Jingui ; Wickert, Jens (2017-07-12)

Global Navigation Satellite System (GNSS) signals can be exploited to remotely sense atmosphere and land and ocean surface to retrieve a range of geophysical parameters. This paper proposes two new methods, termed as power-summation of differential Delay-Doppler Maps (PS-D) and pixel-number of differential Delay-Doppler Maps (PN-D), to distinguish between sea ice and sea water using differentia...

Validation and Assessment of Multi-GNSS Real-Time Precise Point Positioning in Simulated Kinematic Mode Using IGS Real-Time Service

Wang, Liang ; Li, Zishen ; Ge, Maorong ; Neitzel, Frank ; Wang, Zhiyu ; Yuan, Hong (2018-02-23)

Precise Point Positioning (PPP) is a popular technology for precise applications based on the Global Navigation Satellite System (GNSS). Multi-GNSS combined PPP has become a hot topic in recent years with the development of multiple GNSSs. Meanwhile, with the operation of the real-time service (RTS) of the International GNSS Service (IGS) agency that provides satellite orbit and clock correctio...

Assessment of Different Stochastic Models for Inter-System Bias between GPS and BDS

Jiang, Nan ; Xu, Tianhe ; Xu, Yan ; Xu, Guochang ; Schuh, Harald (2019-04-25)

Inter-system bias (ISB) will affect accuracy and processing time in integrated precise point positioning (PPP), and ISB stochastic models will largely determine the quality of ISB estimation. Thus, the impacts of four different stochastic models of ISB processing will be assessed and studied in detail to further reveal the influence of ISB in positioning. They are ISB-PW considering ISB as a pi...

Estimating the Impact of Global Navigation Satellite System Horizontal Delay Gradients in Variational Data Assimilation

Zus, Florian ; Douša, Jan ; Kačmařík, Michal ; Václavovic, Pavel ; Dick, Galina ; Wickert, Jens (2018-12-28)

We developed operators to assimilate Global Navigation Satellite System (GNSS) Zenith Total Delays (ZTDs) and horizontal delay gradients into a numerical weather model. In this study we experiment with refractivity fields derived from the Global Forecast System (GFS) available with a horizontal resolution of 0.5°. We begin our investigations with simulated observations. In essence, we extract t...