A5046221138- GNSS positioning and interference
- Geophysics and Gravity Measurements
- Inertial Sensor and Navigation
- Ionosphere and magnetosphere dynamics
- Advanced Frequency and Time Standards
- Target Tracking and Data Fusion in Sensor Networks
- Seismology and Earthquake Studies
- Earthquake Detection and Analysis
- Cooperative Communication and Network Coding
- Spacecraft Design and Technology
- Advanced Wireless Communication Techniques
- Spaceflight effects on biology
- Geological and Geophysical Studies
- Radio Astronomy Observations and Technology
- Fungal Biology and Applications
- Advanced Electrical Measurement Techniques
- Mycorrhizal Fungi and Plant Interactions
- Methane Hydrates and Related Phenomena
- Health, Environment, Cognitive Aging
- Water Systems and Optimization
- Geomagnetism and Paleomagnetism Studies
- Advanced Statistical Methods and Models
- Advanced MIMO Systems Optimization
- Botanical Research and Applications
- Indoor and Outdoor Localization Technologies
GFZ Helmholtz Centre for Geosciences
2020-2024
Technische Universität Berlin
2021
Institut de physique du globe de Paris
2021
Technical University of Munich
2011-2020
Reconstructing the ionosphere with high precision is critical for understanding space weather and its impacts on satellite communications, navigation, radar systems. Traditionally, ionospheric studies rely ionosondes measurements as well ground based Total Electron Content derived from GNSS (Global Navigation Satellite System) local measurements, but also Radio Occultation (RO) insitu electron density Low Earth Orbiting Satellites (LEO) global measurements. While RO has been instrumental in...
Global navigation satellite systems (GNSS) are used for various applications in the Earth and atmospheric sciences, navigation, surveying mapping, as well early warning geo-hazards. Solutions often required to not only be of high accuracy, integrity, continuity, but also available real-time with a delay few seconds. A prerequisite precise point positioning (PPP) orbit clock products. While orbits can predicted precision, at least hours, clocks have estimated using GNSS data from global...
Abstract The use of the GLONASS legacy signals for real-time kinematic positioning is considered. Due to FDMA multiplexing scheme, conventional CDMA observation model has be modified restore integer estimability ambiguities. This modification a strong impact on capabilities. In particular, ambiguity resolution performance this clearly weaker than systems, so that fast and reliable full usually not feasible standalone GLONASS, adding data in multi-GNSS approach can reduce combined model....
In differential global navigation satellite system positioning applications with short to moderate observation time spans, carrier phase ambiguity resolution is required obtain precise coordinate estimates. Depending on the length of baseline, atmospheric delays between two receivers may have be considered, thus weakening underlying model. this contribution, we study single-, dual-, and triple-frequency, single- combined-system GPS/Galileo cases short, medium-length, long baselines an...
Abstract The GPS satellite transmitter antenna phase center offsets (PCOs) can be estimated in a global adjustment by constraining the ground station coordinates to current International Terrestrial Reference Frame (ITRF). Therefore, derived PCO values rest on terrestrial scale parameter of frame. Consequently, transfer this any subsequent GNSS solution. A method derive scale-independent PCOs without introducing frame is prerequisite an independent factor that contribute datum definition...
Global navigation satellite systems provide ranging based positioning and timing services. The use of the periodic carrier-phase signals is key to fast accurate solutions, given that inherent ambiguities measurements are correctly resolved. idea partial ambiguity resolution resolve a subset all ambiguities, which enables faster solutions but does not fully exploit high precision measurements. Theory, methods, algorithms for discussed analyzed with simulated real data.
Abstract Global navigation satellite system (GNSS) networks with multi‐frequency data can be used to monitor the activity of Earth's ionosphere and generate global maps vertical total electron content (VTEC). This article introduces evaluates operational GFZ VTEC maps. The processing is based on a rigorous least squares approach using uncombined code phase observations, does not entail leveling techniques. A single‐layer model spherical harmonic representation used. solutions are generated...
Abstract Ambiguity resolution enabled precise point positioning (PPP-AR or PPP-RTK) without atmospheric corrections requires the user to estimate tropospheric and ionospheric delay parameters. The presence of unconstrained ionosphere parameters impedes fast reliable ambiguity resolution, so a time-to-first-fix around 30 min for GPS-only solutions is generally reported, which can, some extent, be reduced when combining multiple GNSS. In this contribution, we investigate capabilities almost...
The key to high precision parameter estimation in global navigation satellite system (GNSS) applications is properly deal with the integer valued carrier-phase ambiguities. class of estimators fixes all ambiguities values. This can also decrease estimates non-ambiguity parameters, if fixing incorrect. best integer-equivariant (BIE) estimator optimal sense minimizing mean-squared error (MSE) both and real regardless float solution. However, BIE comprises a search space ambiguities, whose...
Satellites with dual-frequency Global Navigation Satellite Systems (GNSS) receivers can measure integrated electron density, known as slant Total Electron Content (sTEC), between the receiver and transmitter. Precise relative variations of sTEC are achievable using phase measurements on L1 L2 frequencies, yielding around 0.1 TECU or better.However, CubeSats like Spire LEMUR, simpler setups code noise in order several meters, face limitations absolute accuracy. Their accuracy, determined by...
Abstract Satellites with dual‐frequency Global Navigation Satellite Systems (GNSS) receivers can measure integrated electron density, known as slant Total Electron Content (sTEC), between the receiver and transmitter. Precise relative variations of sTEC are achievable using phase measurements on L1 L2 frequencies, yielding an accuracy around 0.1 TECU or better. However, CubeSats like Spire LEMUR, simpler setups (e.g., patch antennas) code noise in order several meters, face limitations...
Abstract The problem of integer or mixed integer/real valued parameter estimation in linear models is considered. It a well-known result that for zero-mean additive Gaussian measurement noise the least-squares estimator optimal sense maximizing probability correctly estimating full vector parameters. In applications such as global navigation satellite system ambiguity resolution, it can be beneficial to resolve only subset all We derive leads highest possible success rate given and compare...
Reliable real-time kinematic positioning requires the occurrence of incorrect integer ambiguity estimates to be limited a maximum tolerable rate. For long baselines this usually implies convergence times due presence atmospheric delay parameters. Several simulation studies have shown that partial resolution (PAR) techniques are beneficial in terms faster solutions, since it is more likely subset all ambiguities can reliably resolved rather than full set, but they also result precision...
Introducing atmospheric delays in the GNSS RTK positioning model significantly weakens ambiguity resolution performance, causing for instance long times to reliably fix ambiguities when differential ionospheric have be estimated. In order overcome this problem, combination of two strategies is proposed paper: joint processing five and partial resolution. For GLONASS, recently introduced integer estimable FDMA from [1] employed. We analyze different schemes, both with simulations real data an...
Over the past years, International GNSS Service (IGS) has been putting efforts into extending its service towards Multi-GNSS Experiment and Pilot Project (MGEX). Several MGEX Analysis Centers (ACs) contribute by providing solutions containing not only GPS GLONASS but also Galileo, BeiDou, QZSS. The orbit clock combination is a product that still consolidated inside IGS requires studies in order to provide consistent solution. In this contribution, we present least-squares framework for...