Search results for "synthetic aperture radar"
showing 10 items of 61 documents
Synthetic Aperture Lensless Digital Holographic Microscopy (SALDHM) for Superresolved Biological Imaging
2013
Lensless digital holographic microscopy (LDHM) relates with the capability to achieve microscopic imaging working without lenses in the regime of holography. LDHM uses an extremely simplified setup and provides micron-range lateral and depth resolutions in three-dimensional (3D) imaging. Typically, LDHM uses a pinhole to provide spherical divergent illumination over the sample. Then, two different basic schemes are usually adopted for providing holographic recording. The first one assumes the interference between two in-line waves since diffraction by the sample can be considered as a perturbation of the reference wave. The second scheme uses an external reference beam in an off-line config…
Superresolved phase-shifting Gabor holography by CCD shift
2009
Holography in the Gabor regime is restricted to weak diffraction assumptions. Otherwise, diffraction prevents an accurate recovery of the object's complex wavefront. We have recently proposed a modified Gabor-like setup to extend Gabor's concept to any sample provided that it be non-diffusive. However, the resolution of the final image becomes limited as a consequence of the additional elements considered in the proposed setup. In this paper we present an experimental approach to overcome such a limitation in which the former configuration is used while the CCD camera is shifted to different off-axis positions in order to generate a synthetic aperture. Thus, once the whole image set is reco…
An integrated geodetic and InSAR technique for the monitoring and detection of active faulting in southwestern Sicily
2020
We present the results of the analysis of GNSS (Global Navigation Satellite System) and InSAR (Interferometric synthetic-aperture radar) data collected in the frame of a project financed by the “Struttura Terremoti” of INGV (Istituto Nazionale di Geofisica e Vulcanologia). Combined investigations pointed out for potential seismogenic sources for destructive earthquakes recorded in southwestern Sicily, including the 1968 Belice earthquake sequence and that supposed to have destroyed the Greek city of Selinunte which, according to geoarcheological data experienced two earthquakes in historical times. Our approach is aimed to evaluate the current deformation rate in SW Sicily and to improve th…
Sensitivity of the C-band SRTM DEM Vertical Accuracy to Terrain Characteristics and Spatial Resolution
2008
This work reports the results of a careful regional analysis of the SRTM DEM (Shuttle Radar Topography Mission – Digital Elevation Model) vertical accuracy as a function of both topography and Land-Use/Land Cover (LULC). Absolute vertical errors appear LULC-dependent, with some values greater than the stated accuracy of the SRTM dataset, mostly over forested areas. The results show that the structure of the errors is well modeled by a cosine power n of the local incidence angle (θloc). SRTM quality is further assessed using slope and topographical similarity indexes. The results show a lower relative accuracy on slope with a R2 = 0.5 and a moderate agreement (Kappa ≈ 0.4) between SRTM- and …
Monitoring peatland water table depth with optical and radar satellite imagery
2022
Peatland water table depth (WTD) and wetness have widely been monitored with optical and synthetic aperture radar (SAR) remote sensing but there is a lack of studies that have used multi-sensor data, i.e., combination of optical and SAR data. We assessed how well WTD can be monitored with remote sensing data, whether multi-sensor approach boosts explanatory capacity and whether there are differences in regression performance between data and peatland types. Our data consisted of continuous multiannual WTD data from altogether 50 restored and undrained Finnish peatlands, and optical (Landsat 5–8, Sentinel-2) and Sentinel-1 C-band SAR data processed in Google Earth Engine. We calculated rando…
Landslide Impacts on Agrigento’s Cathedral Imaged with Radar Interferometry
2013
ERS1/2 (1992–2000), ENVISAT (2002–2008) and RADARSAT1 (2003–2007) satellite data, processed with Persistent Scatterer Interferometry, are exploited to study the historic urban area of Agrigento, Italy, whose structural stability is threatened by retrogressive landslide processes. Up to 2–5mm/year of line-of-sight displacement are observed in 1992–2008 on the staircase and the left aisle of the Cathedral. Displacement acceleration to 13–15mm/year is measured in July 2006–May 2007, in the northern portion of the churchyard, in front of the left aisle. The areas moving at higher rates, located at the edge of the NW slope of Girgenti hill, correspond to those showing major structural damages. A…
Development of the International Severe Asthma Registry (ISAR): A Modified Delphi Study
2019
BACKGROUND: The lack of centralised data on severe asthma has resulted in a scarcity of information about the disease and its management. The development of a common data collection tool for the International Severe Asthma Registry (ISAR) will enable standardised data collection, subsequently enabling data interoperability.OBJECTIVES: To create a standardised list of variables for the first international registry for severe asthma via expert consensus.METHODS: A modified Delphi process was used to reach consensus on a minimum set of variables to capture in ISAR: the core variables. The Delphi panel brought together 27 international experts in the field of severe asthma research. The process…
Sensitivity analysis on the relationship between vegetation growth and multi-polarized radar data
2009
Spatially distributed soil moisture is required for watershed applications such as drought and flood prediction, crop irrigation scheduling, etc. In particular, an accurate assessment of the spatial and temporal variation of soil moisture is necessary to improve the predictive capability of runoff models, and for improving and validating hydrological processes forecasting. In recent years, several models have been developed in order to retrieve soil moisture using RADAR data. However, these models need precise prior knowledge about surface roughness. Within this framework, the present research aims to investigate the capabilities of multi polarimetric RADAR images to overcome the use of in …
Exceeding the resolving imaging power using environmental conditions
2007
We present two approaches that use the environmental conditions in order to exceed the classical Abbe's limit of resolution of an aperture-limited imaging system. At first we use water drops in order to improve the resolving capabilities of an imaging system using a time-multiplexing approach. The limit for the resolution improvement capabilities is equal to the size of the rain drops. The rain drops falling close to the imaged object act as a sparse and random high-resolution mask attached to it. By applying proper image processing, the center of each falling drop is located, and the parameters of the encoding grating are extracted from the captured set of images. The decoding is done digi…
SENTINEL-1 for wheat mapping and soil moisture retrieval
2015
The main objective of this study is to assess the use of Sentinel-1 (S-1) data for surface soil moisture (SSM) retrieval and wheat mapping (WM) at high spatial resolution (e.g. 100–500m), which constitute valuable information for improving crop yield forecast at large scale. A knowledge based classification method and a SSM retrieval algorithm, developed in view of the European Space Agency Sentinel-1 mission, have been applied to a time series of S-1A data collected from October 2014 to April 2015 over a well-documented agricultural site in southern Italy. In particular, observations of SSM content recorded by a network of ground stations deployed in an experimental farm have been used to …