S. Quegan

S. Quegan
The University of Sheffield | Sheffield · School of Mathematics and Statistics

About

314
Publications
52,572
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12,025
Citations
Citations since 2017
46 Research Items
4664 Citations
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20172018201920202021202220230200400600800
20172018201920202021202220230200400600800
20172018201920202021202220230200400600800
Introduction
Skills and Expertise

Publications

Publications (314)
Article
Shaun Quegan discusses the upcoming ESA BIOMASS mission, charged with monitoring the health of Earth's forests.
Article
Full-text available
Forests contribute to climate change mitigation through carbon storage and uptake, but the extent to which this carbon pool varies in space and time is still poorly known. Several Earth Observation missions have been specifically designed to address this issue, e.g. NASA's GEDI, NASA-ISRO's NISAR and ESA's BIOMASS. Yet, all these missions' products...
Article
Full-text available
Space-based Earth observation (EO), in the form of long-term climate data records, has been crucial in the monitoring and quantification of slow changes in the climate system—from accumulating greenhouse gases (GHGs) in the atmosphere, increasing surface temperatures, and melting sea-ice, glaciers and ice sheets, to rising sea-level. In addition to...
Article
Statistically rigorous inferences in the form of confidence intervals for map-based estimates require model-based inferential methods. Model-based mean square errors (MSE) incorporate estimates of both residual variability and sampling variability, of which the latter includes population unit variance estimates and pairwise population unit covarian...
Article
Full-text available
Over the past decade, several global maps of above-ground biomass (AGB) have been produced, but they exhibit significant differences that reduce their value for climate and carbon cycle modelling, and also for national estimates of forest carbon stocks and their changes. The number of such maps is anticipated to increase because of new satellite mi...
Article
Full-text available
Tropical forests play a key role in the global carbon and hydrological cycles, maintaining biological diversity, slowing climate change, and supporting the global economy and local livelihoods. Yet, rapidly growing populations are driving continued degradation of tropical forests to supply wood products. The United Nations (UN) has developed the Re...
Article
Full-text available
Selective logging is the primary driver of forest degradation in the tropics and reduces the capacity of forests to harbour biodiversity, maintain key ecosystem processes, sequester carbon, and support human livelihoods. While the preceding decade has seen a tremendous improvement in the ability to monitor forest disturbances from space, large-scal...
Article
Full-text available
This paper analyses the effects of system distortions (crosstalk and channel imbalance), Faraday rotation and system noise on estimates of the cross-polarized backscattering coefficient, \mathbit{\sigma}_{\mathbit{hv}}^\mathbf{0}, by a spaceborne synthetic aperture radar (SAR). Modelling the unknown system errors and noise by a joint complex Gaussi...
Article
Aim The carbon sink in tropical forests is a highly uncertain component of the global carbon budget. An understanding of the processes controlling this sink requires better quantification of carbon allocation, stocks and turnover times. Location Tropical forests. Time period 2010–2017. Major taxa studied Tropical forest ecosystem. Methods We de...
Book
Full-text available
the full text can be found at: https://lpvs.gsfc.nasa.gov/PDF/CEOS_WGCV_LPV_Biomass_Protocol_2021_V1.0.pdf
Article
Full-text available
The terrestrial forest carbon pool is poorly quantified, in particular in regions with low forest inventory capacity. By combining multiple satellite observations of synthetic aperture radar (SAR) backscatter around the year 2010, we generated a global, spatially explicit dataset of above-ground live biomass (AGB; dry mass) stored in forests with a...
Article
Full-text available
This paper introduces the CASINO (CAnopy backscatter estimation, Subsampling, and Inhibited Nonlinear Optimisation) algorithm for above-ground biomass (AGB) estimation in tropical forests using P-band (435 MHz) synthetic aperture radar (SAR) data. The algorithm has been implemented in a prototype processor for European Space Agency's (ESA's) 7th Ea...
Article
Climate Data Records (CDRs) of Essential Climate Variables (ECVs) as defined by the Global Climate Observing System (GCOS) derived from satellite instruments help to characterize the main components of the Earth system, to identify the state and evolution of its processes, and to constrain the budgets of key cycles of water, carbon and energy. The...
Article
Full-text available
Tropical forests harbour the highest biodiversity on the planet and are essential to human livelihoods and the global economy. However, continued loss and degradation of forested landscapes, coupled with a rapidly rising global population is placing incredible pressure on forests globally. The United Nations has developed the Reducing Emissions fro...
Article
Full-text available
The characterization of carbon stocks and dynamics at the national level is critical for countries engaging in climate change mitigation and adaptation strategies. However, several tropical countries, including Kenya, lack the essential information typically provided by a complete national forest inventory. Here we present the most detailed and rig...
Preprint
Full-text available
The terrestrial forest carbon pool is poorly quantified, in particular in regions with low forest inventory capacity. By combining multiple satellite observations of synthetic aperture radar (SAR) backscatter around the year 2010, we generated a global, spatially explicit dataset of above-ground forest biomass (dry mass, AGB) with a spatial resolut...
Article
Full-text available
Enhanced silicate rock weathering (ERW), deployable with croplands, has potential use for atmospheric carbon dioxide (CO2) removal (CDR), which is now necessary to mitigate anthropogenic climate change¹. ERW also has possible co-benefits for improved food and soil security, and reduced ocean acidification2–4. Here we use an integrated performance m...
Article
Full-text available
Climate Data Records (CDRs) of Essential Climate Variables (ECVs) as defined by the Global Climate Observing System (GCOS) derived from satellite instruments help to characterize the main components of the Earth system, to identify the state and evolution of its processes, and to constrain the budgets of key cycles of water, carbon and energy. The...
Article
Full-text available
Frequent cloud cover in the tropics significantly affects the observation of the surface by satellites. This has enormous implications for current approaches that estimate greenhouse gas (GHG) emissions from fires or map fire scars. These mainly employ data acquired in the visible to middle infrared bands to map fire scars or thermal data to estima...
Preprint
Full-text available
Selective logging is the primary driver of forest degradation in the tropics and reduces the capacity of forests to harbour biodiversity, maintain key ecosystem processes, sequester carbon, and support human livelihoods. While the preceding decade has seen a tremendous improvement in the ability to monitor forest disturbances from space, advances i...
Article
Full-text available
BIOMASS is ESA’s seventh Earth Explorer mission, scheduled for launch in 2022. The satellite will be the first P-band SAR sensor in space and will be operated in fully polarimetric interferometric and tomographic modes. The mission aim is to map forest above-ground biomass (AGB), forest height (FH) and severe forest disturbance (FD) globally with a...
Article
A new processing technique, i.e., ground cancellation, which removes the ground signal from a pair of interferometric synthetic aperture radar (SAR) images, is used to emphasize the response from above-ground targets. This technique is of particular interest when studying forest canopies using low-frequency signals able to reach the underlying grou...
Article
Full-text available
The amount and spatial distribution of forest aboveground biomass (AGB) were estimated using a range of regionally developed methods using Earth Observation data for Poland, Sweden and regions in Indonesia (Kalimantan), Mexico (Central Mexico and Yucatan peninsula), and South Africa (Eastern provinces) for the year 2010. These regions are represent...
Article
Full-text available
Secondary forests (SF) are important carbon sinks, removing CO2 from the atmosphere through the photosynthesis process and storing photosynthates in their aboveground live biomass (AGB). This process occurring at large-scales partially counteracts C emissions from land-use change, playing, hence, an important role in the global carbon cycle. The ab...
Article
This paper presents an analysis of a logarithmic relationship between P-band cross-polarized backscatter from synthetic aperture radar (SAR) and aboveground biomass (AGB) across different forest types based on multiple airborne datasets. It is found that the logarithmic function provides a statistically significant fit to the observed relationship...
Preprint
Full-text available
Secondary forests (SF) are important carbon sinks, removing CO2 from the atmosphere through the photosynthesis process and storing photosynthates in their aboveground live biomass (AGB). This process occurring at large-scales partially counteracts C emissions from land-use change, playing, hence, an important role in the global carbon cycle. The ab...
Article
A significant amount of the data acquired by sun-synchronous space-borne low-frequency synthetic aperture radars (SARs) through the postsunset equatorial sector are distorted by the ionospheric scintillations due to the presence of plasma irregularities and their zonal and vertical drift. In the focused SAR images, the distortions due to the postsu...
Article
Full-text available
The global carbon cycle is an important component of the Earth system and it interacts with the hydrology, energy and nutrient cycles as well as ecosystem dynamics. A better understanding of the global carbon cycle is required for improved projections of climate change including corresponding changes in water and food resources and for the verifica...
Article
Full-text available
The magnitude of the global terrestrial carbon pool and related fluxes to and from the atmosphere are still poorly known. The European Space Agency P-band radar BIOMASS mission will help to reduce this uncertainty by providing unprecedented information on the distribution of forest above-ground biomass (AGB), particularly in the tropics where the g...
Article
Full-text available
Turnover concepts in state-of-the-art global vegetation models (GVMs) account for various processes, but are often highly simplified and may not include an adequate representation of the dominant processes that shape vegetation carbon turnover rates in real forest ecosystems at a large spatial scale. Here, we evaluate vegetation carbon turnover pro...
Article
Turnover concepts in state-of-the-art global vegetation models (GVMs) account for various processes, but are often highly simplified and may not include an adequate representation of the dominant processes that shape vegetation carbon turnover rates in real forest ecosystems at a large spatial scale. Here, we evaluate vegetation carbon turnover pro...
Technical Report
Full-text available
This plan describes the proposed implementation of a global observing system for climate, building on current actions. It sets out a way forward for science and technological innovations for the earth observation programmes of space agencies, and for the national implementation of climate observing systems and networks.
Article
Full-text available
Atmospheric haze causes visibility to drop, therefore affecting data acquired using optical sensors on board remote sensing satellites. Haze modifies the spectral signatures of land cover classes and reduces classification accuracy so causing problems to users of remote sensing data. This paper addresses general concepts of haze removal from remote...
Article
A correction methodology for distortions induced by ionospheric scintillation on fully polarimetric synthetic aperture radar (SAR) data is proposed. The correction is based on deriving the phase distortion induced by the ionosphere from Faraday rotation estimates. The estimated phase distortion is then used for correction. In order to compensate th...
Article
Full-text available
Fire provides an impulsive and stochastic pathway for carbon from the terrestrial biosphere to enter the atmosphere. Despite fire emissions being of similar magnitude to net ecosystem exchange in many biomes, even the most complex dynamic vegetation models (DVMs) embedded in general circulation models contain poor representations of fire behaviour...
Article
Full-text available
Radio waves traversing the Earth's ionosphere suffer from Faraday rotation with noticeable effects on measurements from lower frequency space-based radars, but these effects can be easily corrected given estimates of the Faraday rotation angle, i.e., $Omega$. Several methods to derive $Omega$ from polarimetric measurements are known, but they are a...
Article
Full-text available
For long-wavelength space-based radars, such as the P-band radar on the recently selected European Space Agency BIOMASS mission, system distortions (crosstalk and channel imbalance), Faraday rotation, and system noise all combine to degrade the measurements. A first-order analysis of these effects on the measurements of the polarimetric scattering...
Research
Full-text available
Enhanced SAR detection of deforestation by including textural information (variability of adjacent pixels).
Article
Tropical coverage by Envisat ASAR is sparse in space and time and has limited value for monitoring deforestation. The only available dual-polarized multitemporal dataset over Riau province, Indonesia (nine images in a single year), is used to distinguish and monitor tropical plantations and their dynamics and is compared with annual L-band PALSAR d...
Conference Paper
Full-text available
This is a selection of results of the North State project, that demonstrate how innovative methods applied to the new Sentinel data streams can be combined with models to monitor carbon and water fluxes for pan-boreal Europe.
Book
Full-text available
In 2009, Thales Alenia Space and Suds-Concepts issued a book called “Climate Change and Satellites”, bringing together an international network of scientists, users, and representatives of major space agencies. With a circulation of over 15,000, mainly in the scientific, governmental and CC community, it was recognized as a leading publication in i...
Article
The P-band synthetic aperture radar of the European Space Agency BIOMASS mission will be affected by ionospheric phase scintillation at high latitudes, which introduces a random high-order azimuth phase error. The dependence of the performance of the phase gradient autofocus (PGA) algorithm for scintillation compensation on the strength of ionosphe...
Conference Paper
Full-text available
The objective of project North State, funded by Framework Program 7 of the European Union, is to develop innovative data fusion methods that exploit the new generation of multi-source data from Sentinels and other satellites in an intelligent, self-learning framework. The remote sensing outputs are interfaced with state-of-the-art carbon and water...
Article
Full-text available
Fire provides an impulsive and stochastic pathway for carbon from the terrestrial biosphere to enter the atmosphere. Despite fire emissions being of similar magnitude to Net Ecosystem Exchange in many biomes, even the most complex Dynamic Vegetation Models (DVMs) embedded in General Circulation Models contain poor representations of fire behaviour...
Article
Full-text available
Remote sensing data have long been the primary source for land cover map derivation. Nevertheless, for countries within haze-affected regions such as Malaysia, the existence of haze in the atmosphere tends to degrade the data quality. Such scenario is due to attenuation of recorded reflectances in which consequently affects the land cover classific...
Conference Paper
The paper studies tropical deforestation detection in Riau province, Indonesia with L-band ALOS PALSAR and Cband ENVISAT ASAR data. Multiple change measures as SAR image intensity, texture, and temporal variations of ScanSAR time series are extracted and employed for deforestation detection. These measures are then combined for improving the detect...
Article
Spaceborne linearly polarimetric synthetic aperture radar (SAR) provides information about surface properties and scatterer types by measuring the covariances between images formed using orthogonally polarized radio waves. However, ionospheric Faraday rotation (FR) and system calibration errors alter the balance in the polarimetric channels and dis...
Article
Full-text available
A globally integrated carbon observation and analysis system is needed to improve the fundamental understanding of the global carbon cycle, to improve our ability to project future changes, and to verify the effectiveness of policies aiming to reduce greenhouse gas emissions and increase carbon sequestration. Building an integrated carbon observati...
Article
ALOS PALSAR has provided a five-year archive of systematic global tropical forest coverage, released as slope-corrected and ortho-rectified 50 m mosaic products by JAXA, which are of great help to monitor forest changes. Based on the mosaics, a map of deforestation between the years 2007 and 2008 is built for Riau province, Indonesia, achieving a d...
Article
Full-text available
An increasing number of studies have demonstrated significant climatic and ecological changes occurring in the northern latitudes over the past decades. As coupled Earth-system models attempt to describe and simulate the dynamics and complex feedbacks of the Arctic environment, it is important to reduce their uncertainties in short-term predicti...
Article
Full-text available
The European Space Agency is conducting studies for a low-earth orbiting polarimetric synthetic aperture radar called BIOMASS to provide global measurements of forest biomass and tree height. Phase scintillation across the synthetic aperture caused by ionospheric irregularities can degrade the impulse response function (IRF) and cause squinting, an...
Article
Full-text available
The aims of this study are to investigate the spectral properties of cloud and to carry out cloud detection and masking using MODIS (Moderate-resolution Imaging Spectroradiometer) data. To do this we make use of the spectrally rich satellite data provided by MODIS sensor, which is equipped with 36 bands ranging from visible to thermal wavelengths....
Article
Full-text available
Haze occurs almost every year in Malaysia and is caused by smoke which originates from forest fire in Indonesia. It causes visibility to drop, therefore affecting the data acquired for this area using optical sensor such as that on board Landsat satellite. The effects of haze on the data can be observed from the spectral and statistical properties...
Article
Full-text available
In atmospheric haze studies, it is almost impossible to obtain remote sensing data which have the required haze concentration levels. This problem can be overcome if we can generate haze layer based on the properties of real haze to be integrated with remote sensing data. This work aims to generate remote sensing datasets that have been degraded wi...