A5082045575- Geophysics and Gravity Measurements
- GNSS positioning and interference
- Soil Moisture and Remote Sensing
- earthquake and tectonic studies
- Oceanographic and Atmospheric Processes
- Ionosphere and magnetosphere dynamics
- Climate variability and models
- Geophysical and Geoelectrical Methods
- Tropical and Extratropical Cyclones Research
- Geology and Paleoclimatology Research
- Inertial Sensor and Navigation
- Time Series Analysis and Forecasting
- Methane Hydrates and Related Phenomena
- Cryospheric studies and observations
- Ocean Waves and Remote Sensing
- Coastal and Marine Management
- Earthquake Detection and Analysis
- Atmospheric and Environmental Gas Dynamics
- Flood Risk Assessment and Management
- Child Abuse and Trauma
- Target Tracking and Data Fusion in Sensor Networks
- Scientific Research and Discoveries
- Radio Wave Propagation Studies
- Geological and Geochemical Analysis
- Synthetic Aperture Radar (SAR) Applications and Techniques
Cwm Taf University Health Board
2025
National Oceanography Centre
2015-2024
Douglas Mental Health University Institute
2024
Universidade Federal do Rio Grande do Sul
2021-2023
NOAA National Geodetic Survey
2022
University of New Brunswick
2022
IP Australia
2021
British Oceanographic Data Centre
2004-2019
Natural Environment Research Council
2016
Laboratoire des Sciences de l’Information et de la Communication
2002-2007
A total of 954 continuous GPS position time series from 414 individual sites in nine different solutions were analyzed for noise content using maximum likelihood estimation (MLE). The lengths the varied around 16 months to over 10 years. MLE was used analyze data two ways. In first analysis assumed be white only, a combination plus flicker noise, or random walk noise. For second spectral index and amplitude power law estimated simultaneously with where globally distributed, can best...
We analyze time series of daily positions estimated from data collected by 10 continuously monitoring Global Positioning System (GPS) sites in southern California during the 19‐month period between June 28, 1992 ( M w =7.3), Landers and January 17, 1994 =6.7), Northridge earthquakes. Each exhibits a linear tectonic signal significant colored noise. Spectral power at frequencies range 5 yr −1 to 0.5 d is dominated white noise or possibly fractal several orders magnitude higher than what would...
Abstract We use 2.5 to 14 years long position time series from >800 continuous Global Positioning System (GPS) stations study vertical deformation rates in the Euro‐Mediterranean region. estimate and remove common mode errors using a principal component analysis, obtaining significant gain signal‐to‐noise ratio of displacements data. Following results maximum likelihood estimation which gives mean spectral index ~ −0.7, we adopt power law + white noise stochastic model estimating final...
Interferometric synthetic aperture radar (INSAR), like other astronomic and space geodetic techniques, is limited by the spatially temporally variable delay of electromagnetic waves propagating through neutral atmosphere. Statistical analysis these variations, from a wide variety instruments, reveals power law dependence on frequency that characteristic elementary (Kolmogorov) turbulence. A statistical model for major component fluctuations, “wet” component, has previously been developed...
The results from a carefully implemented GPS analysis, using strategy adapted to determine accurate vertical station velocities, are presented. stochastic properties of our globally distributed position time series were inferred, allowing the computation reliable velocity uncertainties. Most uncertainties several times smaller than 1–3 mm/yr global sea level change, and hence velocities could be applied correct long tide gauge records for land motion. trends obtained in ITRF2005 reference...
The accuracy of Global Positioning System (GPS) time series is degraded by the presence offsets. To assess effectiveness methods that detect and remove these offsets, we designed managed Detection Offsets in GPS Experiment. We simulated mimicked realistic data consisting a velocity component, white flicker noises (1/f spectrum noises) composed an additive model. set was made available to analysis community without revealing several groups conducted blind tests with range detection...
[1] Bedrock uplift in Antarctica is dominated by a combination of glacial isostatic adjustment (GIA) and elastic response to contemporary mass change. Here, we present spatially extensive GPS observations Antarctic bedrock uplift, using 52% more stations than previous studies, giving enhanced coverage, with improved precision. We observe rapid the northern Peninsula. After considering rebound, data suggests that modeled or empirical GIA signals are often over-estimated, particularly...
This paper presents estimates of rates mean sea level (MSL) change around the UK, based on a larger tide gauge data set and more accurate analysis methods than have been employed so far. The spatial variation trend in MSL is found to be similar that inferred from geological information advanced geodetic techniques, which conclusion arrived at previous studies. trends for 1901 onwards are estimated 1.4 ± 0.2 mm yr−1 those geology or methods, suggesting regional rise climate origin several...
Abstract A standard geodetic GPS receiver and a conventional Aquatrak tide gauge, collocated at Friday Harbor, Washington, are used to assess the quality of 10 years water levels estimated from sea surface reflections. The results improved by accounting for (tidal) motion reflecting signal propagation delay troposphere. RMS error individual level estimates is about 12 cm. Lower measured slightly more accurately than higher levels. Forming daily mean reduces difference with gauge data...
It is well known that sea level variations exhibit temporal correlation. This sometimes ignored in the estimation process of rise or taken into account using a first-order autoregressive model. We have verified this stochastic model accurate for yearly tide gauge and reconstruction time-series but it underestimates real rate uncertainty satellite altimetry monthly data by factor 1.3–1.5 even 2. Similar results were found acceleration. An original finding 13–17 per cent data, we random walk...
Abstract Recent studies have demonstrated the utility of ground‐based Global Navigation Satellite Systems‐Multipath Reflectometry (GNSS‐MR) for sea level studies. Typical root‐mean‐square (RMS) differences GNSS‐MR‐derived time series with respect to nearby tide gauges are on order 6–40 cm, sufficiently accurate estimate tidal and secular variations but possibly biased due delay signal through troposphere. In this study we investigate tropospheric effect from more than 20 GNSS coastal sites...
A major challenge for managing impacts and implementing effective mitigation adaptation strategies coastal zones affected by future sea level (SL) rise is our very limited capacity to predict SL change on scales, over various timescales. Predicting requires the ability monitor simulate a multitude of physical processes affecting SL, from local effects wind waves river runoff remote influences large-scale ocean circulation coast. Here we assess current understanding causes variability...
Site velocities are a common product of continuous Global Positioning System (CGPS) networks. Estimation site from their time series can be biased if offsets present. If left uncorrected, dominate velocity uncertainties. Artificial (nontectonic) discontinuities may arise environmental and equipment changes or human intervention error. Analysis present GPS data sets reveals that on component by basis, one offset occurs every 9 years, although it could as frequent 2 years. The effect...
The southern California Permanent GPS Geodetic Array (PGGA) was established in 1990 across the Pacific‐North America plate boundary to continuously monitor crustal deformation. We describe development of array and time series daily positions estimated for its first 10 sites 19‐month period between June 28, 1992 ( M w =7.3), Landers January 17, 1994 =6.7), Northridge earthquakes. compare displacement rates at four site locations with those reported by Feigl et al. [1993], which were derived...
A total of 96 absolute gravity (AG) measurements at the Membach station and 221 Proudman Oceanographic Laboratory (POL) is analyzed for noise content. The lengths series were around 10 years 8 (Membach). First frequencies lower than 1 cpd studied. This consists in setup‐dependent offsets geophysical colored sources. setup white estimated using continuous relative superconducting (SG) Membach. environmental affecting both AG SG maximum likelihood estimation technique to fit two types...
GPS observations used in geophysical studies are not usually corrected for non‐tidal ocean loading (NTOL) displacement. Here we investigate NTOL effects on 3–4 year height time series from 17 sites around the southern North Sea, and compute displacement according to two models; global ECCO model a high resolution regional model, POLSSM, which covers northwest European continental shelf. To assess susceptibility of estimates NTOL, reprocessed GIPSY PPP daily solutions resulting displacement,...
Previous GRACE-derived ice mass trends and accelerations have almost entirely been based on an assumption that the residuals to a regression model (including also semi-annual, annual tidal aliasing terms) are not serially correlated. We consider change time series for Antarctica show significant autocorrelation is, in fact, present. examine power-law autoregressive models compare them those assume white (uncorrelated) noise. The data do let us separate but both indicate noise uncertainties...
Long‐running, short (≪1 km) GPS baselines offer an insight into the accuracy budget of geophysical estimates inferred from coordinate time series. In this paper, we report on analysis 10 using data spanning several years and examine deviations a constant baseline length. Annual signals with amplitude >0.5 mm are evident in various components at 6 sites, amplitudes exceeding 2.5 two baselines. These largely invariant to elevation cutoff angle. Multipath phase center model errors shown...
We investigate spatial variations in the shape of spectrum sea level variability based on a homogeneously sampled 12 year gridded altimeter data set. present method plotting spectral information as color, focusing periods between 2 and 24 weeks, which shows that significant exist contain useful dynamical information. Using Bayesian Information Criterion, we determine that, typically, fifth‐order autoregressive model is needed to capture structure spectrum. this model, show statistical errors...