48 research outputs found
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Monitoring aquifer-system response to groundwater pumping and artificial recharge
No full textJohn W. Bell, Falk Amelung, Alessandro Ferretti, Marco Bianchi and Fabrizio Novali present a new satellite methodology for detecting and measuring long-term and seasonal aquifer-system response to pumping and recharge which potentially could be used for oil and/or gas reservoir monitoring
High resolution CSK data for emergency response
No full textOn January 13, 2012, the Italian vessel Costa Concordia wrecked offshore the Giglio Island, along the coast of
Tuscany (Italy). The ship partially sunk, lying on the starboard side on a steep rocky seabed, creating also pernicious
conditions for divers involved in the search and rescue operations. Starting from January 19, the Italian
COSMO-SkyMed (CSK) constellation of was tasked to acquire high resolution images of the wreck. Thanks to
CSK’s short response and revisiting time and its capability to acquire high resolution images in spotlight mode,
satellite data were integrated within the real time, ground-based monitoring system already installed, in order to
provide the Civil Protection authorities with a regular update on the ship stability
Monitoring and understanding crustal deformation by means of GPS and InSAR data
No full textMonitoring deformation of the Earth’s crust by using data acquired by both the GNSS and SAR techniques allows
describing crustal movements with high spatial and temporal resolution. This is a key contribution for achieving a
deeper and better insight of geodynamic processes. Combination of the two techniques provides a very powerful
means, however, before combing the different data sets it is important to properly understand their respective
contribution. For this purpose, strictly simultaneous and long time series would be necessary. This is not, in
general, a common case due to the relatively long SAR satellites revisit time. A positive exception is represented
by the data set of COSMO SKYMed (CSK) images made available for this study by the Italian Space Agency
(ASI). The flyover area encompass the city of Bologna and the smaller nearby town of Medicina where permanent
GPS stations are operational.
At the times of the CSK flyovers, we compared the GPS and SAR Up and East coordinates of a few stations as
well as differential tropospheric delays derived by both techniques. The GPS time series were carefully screened
and corrected for the presence of discontinuities by adopting a dedicated statistical procedure. The comparisons
of both the estimated deformation and the tropospheric delays are encouraging and highlight the need for having
available a more evenly sampled SAR data set
Moving from PS to Slowly Decorrelating Targets: A Prospective View
No full textDuring the last 8 years Permanent Scatterer interferometry (PSInSAR) has been widely used as a powerful tool for
surface deformation monitoring both for scientific and commercial projects. A few years after the introduction of this
technology, it was highlighted how the constraints on the stability of the radar signature of the targets used as opportunistic
measurement points could be too tight. Forcing the PS to be coherent in all interferometric pairs used in the analysis
could cause the loss of information coming from scatterers exhibiting PS behavior only in a subset of SAR images.
Another concern was related to the estimation of the DEM reconstruction: the problem here is to take advantage of the PS
framework trying to extend the set of image pixels where an estimation of the elevation is possible. Apart from geometrical
decorrelation and variations of the Doppler centroid values of the acquisitions, temporal decorrelation phenomena strongly
limit the coherence values of many scatterers within the area of interest. The question arising is whether the presence of
radar scatterers exhibiting high or moderate coherence levels at low temporal baselines (typically one month) can be useful
for real life applications and, in case of positive answer, which algorithms are most suited to extract useful information
from slowly decorrelating scatterers. Although this topic is still the subject of extensive research activities, this paper
summarizes some facts that, in the authors’ opinion, will be the base of any future algorithm. In particular, the analysis
of the coherence matrix computed on a pixel-by-pixel basis is shown to be a key-element of any study of decorrelating
targets. Its modeling can be extremely useful to extract feature parameters for image segmentatio
The COSMO-SkyMed Constellation Monitors the Costa Concordia Wreck
No full textOn 13 January 2012, the Italian vessel, Costa Concordia, wrecked offshore Giglio Island, along the coast of Tuscany (Italy). The ship partially sunk, lying on the starboard side on a 22° steep rocky seabed, making the stability conditions of the ship critically in danger of sliding, shifting and settling. The tilted position of the ship created also pernicious conditions for the divers involved in the search and rescue operations. It became immediately clear that a continuous monitoring of the position and movements of the ship was of paramount importance to guarantee the security of the people working around and within the wreck. Starting from January 19, the Italian constellation of synthetic aperture radar (SAR) satellites, COSMO-SkyMed (CSK), was tasked to acquire high resolution images of the wreck. Thanks to CSK’s short response and revisiting time and its capability to acquire high resolution images in Spotlight mode, satellite data were integrated within the real time, ground-based monitoring system implemented to provide the civil protection authorities with a regular update on the ship stability. Exploitation of both the phase (satellite radar interferometry, InSAR) and amplitude (speckle tracking) information from CSK images, taken along the acquisition orbit, Enhanced Spotlight (ES)-29, revealed a general movement of the translation of the vessel, consistent with sliding toward the east of the hull on the seabed. A total displacement, with respect to the coastline, of 1666 mm and 345 mm of the bow and stern, respectively, was recorded, over the time period of 19 January–23 March 2012
Submillimeter Accuracy of InSAR Time Series: Experimental Validation
No full textAbstract—This paper presents the results of a blind experiment
that is performed using two pairs of dihedral reflectors. The
aim of the experiment was to demonstrate that interferometric
synthetic aperture radar (InSAR) measurements can indeed allow
a displacement time series estimation with submillimeter accuracy
(both in horizontal and vertical directions), provided that the
data are properly processed and the impact of in situ as well as
atmospheric effects is minimized. One pair of dihedral reflectors
was moved a few millimeters between SAR acquisitions, in the
vertical and east–west (EW) directions, and the ground truth was
compared with the InSAR data. The experiment was designed to
allow a multiplatform and multigeometry analysis, i.e., each reflector
was carefully pointed in order to be visible in both Envisat
and Radarsat acquisitions. Moreover, two pairs of reflectors were
used to allow the combination of data gathered along ascending
and descending orbits. The standard deviation of the error is 0.75
mm in the vertical direction and 0.58 mm in the horizontal (EW)
direction. GPS data were also collected during this experiment in
order to cross-check the SAR results
Continuous, semi-automatic monitoring of ground deformation using Sentinel-1 satellites
No full textWe present the continuous monitoring of ground deformation at regional scale using ESA (European Space Agency) Sentinel-1constellation of satellites. We discuss this operational monitoring service through the case study of the Tuscany Region (Central Italy), selected due to its peculiar geological setting prone to ground instability phenomena. We set up a systematic processing chain of Sentinel-1 acquisitions to create continuously updated ground deformation data to mark the transition from static satellite analysis, based on the analysis of archive images, to dynamic monitoring of ground displacement. Displacement time series, systematically updated with the most recent available Sentinel-1 acquisition, are analysed to identify anomalous points (i.e., points where a change in the dynamic of motion is occurring). The presence of a cluster of persistent anomalies affecting elements at risk determines a significant level of risk, with the necessity of further analysis. Here, we show that the Sentinel-1 constellation can be used for continuous and systematic tracking of ground deformation phenomena at the regional scale. Our results demonstrate how satellite data, acquired with short revisiting times and promptly processed, can contribute to the detection of changes in ground deformation patterns and can act as a key information layer for risk mitigation
