Special Issue "Exploitation of Synthetic Aperture Radar Targets Velocities"

A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Remote Sensing Image Processing".

Deadline for manuscript submissions: 31 December 2019.

Special Issue Editors

Prof. Thierry Bouwmans
E-Mail Website
Guest Editor
Universitè la Rochelle 17000 La Rochelle, France
Interests: Data and Sensor Fusion; Low rank plus sparse decomposition; Robust principal component analysis; Image processing; Radar Signal processing
Special Issues and Collections in MDPI journals
Dr. Filippo Biondi
E-Mail Website
Guest Editor
Joint Satellite Remote Sensing Center, Italian MoD, Rome RM, Italy
Interests: Synthetic Aperture Radar (SAR) Spotlight and Stripmap focusing; SAR Interferometry and Differential SAR interferometry; Coherent filtering of SAR images; Precise atmospheric phase error estimation; 3-D SAR and polarimetric SAR Tomography; Polarimetric SAR assisted by Multi Chromatic Analysis (MCA) for target future extraction; Advanced algorithms development for Oil-Spill detection; SAR video production using the single SAR image by MCA; SAR refocusing for maritime surveillance; Low rank plus sparse decomposition for automatic future extraction; Super Resolution by spectrum extrapolation; Polarimetric Permanent Scatterers (PS) for precise 3D reconstruction and precise geolocation (Polarimetric-3-D Targeting); Multidimensional subsidence estimation by multiple look-angles of satellite observations and precise velocity/acceleration estimation
Special Issues and Collections in MDPI journals
Dr. Pietro Milillo
E-Mail Website
Guest Editor
NASA, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
Interests: SAR; InSAR; multi-temporal analysis; cryosphere; natural hazards
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Velocity is a relative parameter that can be detected by synthetic aperture radar (SAR). The range of velocities estimable by SAR can vary from a few millimeters per year up to several meters per seconds and more. In this environment, the observations can be performed using several images or working on a single image. The estimation of target velocity can be assessed considering point targets that are detected inside a few resolution cells or using distributed targets that are detected over a huge number of resolution cells. This Special Issue has the objective of publishing works that explore the velocities generated by any nature of targets and spanned along a wide spectrum.

Millimeters and centimeters per year of velocity are usually generated by the Earth’s deformation, and this kind of activity can be detected by SAR in the Differential SAR Interferometry (DInSAR) configuration. In this environment, the persistent scatter interferometry (PSInSAR) signal processing technique can be successfully applied, processing long temporal series of InSAR data in order to track in time the Earth deformations in space, velocity, and acceleration. This technique is also very applicable for the monitoring of urban areas. The global interferometric SAR phase information is provided by different contributors due to topography, Earth deformation, atmospheric delays, orbit errors, phase ambiguities, and general noise. The estimation of the Earth’s deformations with millimeter precision is possible only by estimating a reliable atmospheric phase screen (APS) that is focused on the perform separation of the interferometric phase contribution due to the Earth’s deformation from all unwanted atmospheric effects. In the radar community, several techniques have been developed to retrieve this parameter, and estimation is possible only by processing a long temporal series of interferometric SAR images and under a special assumption of having temporal and spatial constraints.

Centimeter and decimeter per week velocities are hard to detect using the exploitation of the SAR interferometric phase only. Early detection and early warning are of great importance in giant landslide monitoring. In this context, the exploitation of hybrid-SAR techniques is very important. The technique combines both phase-based and amplitude-based information to detect and monitor large-scale landslides. This ratio of velocities is also held by glaciers, which are nowadays melting in a very fast ratio. In these environments, velocities can also be detected using the same hybrid solutions or non-tracking techniques.

Velocities of one or a few meters per day are detectable exploiting multi-temporal SAR data observed using interferometric geometry. Icebergs play an important role in the climate through the transfer of freshwater and heat between ice sheets and the oceans. In this case, synthetic aperture radar images also offer a robust means of observing and tracking in time icebergs in the often dark and cloud-covered polar areas. The tracking can be performed in some very rare cases by exploiting very short time DInSAR techniques and in most cases using tracking capabilities based on the magnitude exploitation.

Velocities of hundreds of meters to some kilometers per day determine the limit for migrating from a multi-temporal to a single-pass SAR acquisition approach. In this case, the targets can be coherent or distributed. In most cases, this gamma of velocities is estimable using along-track interferometry, which is able to detect the range component of the two-dimensional range-azimuth velocity vector of the targets. Measuring velocities in this spectrum can also be performed by Doppler sub-apertures and pixel tracking. Several applications can be exploited starting from maritime surveillance, terrain surveillance and border monitoring, sea current estimation, rivers velocity estimation, and many other applications.

Velocities of meters and several meters per seconds are produced by man-made objects moving on the ground, sailing on the sea or flying in the sky. The applications devoted to this are moving-target indication (MTI) or ground-MTI (GMTI) radars and data fusion observed by different sensors. Some typical applications are wide-area traffic monitoring, using the scan-MTI mode of some airborne radar sensors or using flexible GMTI mode radars, which may be designed for rapidly monitoring wide areas for moving targets. These kinds of remote sensing will scan environments with different natures to perform target detection from a different aspect and angles with a high revisit rate. An important role in this field is the micro-motion estimation of targets. Bistatic SAR (BSAR) provides strategic advantages in radar imaging. The motions and micro-motions of objects under SAR observations generate Doppler and micro-Doppler effects observable in the received radar echoes. The micro-Doppler effect is typically derived for some vibrating targets observed by bistatic SAR. The corresponding bistatic factor is shown to be a function of the bistatic acquisition geometry. The effect of the target vibration on the focused image has also been shown to be influenced by the acquisition geometry. Deriving reliable vibrational models is useful for the micro-Doppler classification of different targets. Micro-motion observations can be performed observing targets in different electromagnetic bands like X, Ku, Ka and more.

The kilometers per second gamma of velocities is devoted to air and space surveillance. In this environment applications can be well-fitted to track small targets like satellites and debris. Inverse SAR (ISAR) is also welcome in order to image satellites and other types of space equipment detected from the Earth and/or space.

In this SAR investigation environment, we welcome the exploitation of new and innovative techniques:

According to the high-resolution wide swath (HRWS) technique, the exploitation of different strategies for generating separation and the orthogonality of signal ambiguities is a crucial task. In this environment, synthetic aperture radars can be also tailored for future multiple-input multiple-output solutions equipped with multichannel antennas to enable wide-area and high-resolution imaging.

Low-PRF radars: According to the minimum antenna area constraint, synthetic aperture radar systems require a low-pulse repetition frequency (PRF) to image the wide swaths in ocean surface monitoring scenarios. This low PRF solution, if set lower than the Doppler bandwidth, will cause azimuth ambiguities. Several methods can be devoted to mitigating azimuth ambiguities when using an under-sampled SAR system for ship detection and velocity estimation over the open sea. In this context, it appears that several methods are only appropriate for detecting bright targets over the dark backgrounds in which residual energy loss occurs for useful signals. Innovative signal processing techniques are welcome to exploit this interesting task.

GeoSAR: This Earth observation technique uses the motion generated by the orbital interference existing on geosynchronous orbits. The nearly fixed position of the geosynchronous platforms makes GeoSAR systems suitable for continuous monitoring applications. However, using high transmitted powers and large antenna sizes over very long integration times, which can be hours long, can cause signals to decorrelate significantly due to atmospheric changes. As a result, an efficient and precise APS is highly necessary. A reliable strategy for avoiding signal aberrations due to atmospheric parameter variations can be the short-term periodic acquisitions based on Doppler sub-apertures.

This Special Issue invites contributions on the above processes and phenomena and include but are not restricted to the following topics:

  • Earth deformation monitoring;
  • Urban area 3D/4D reconstruction and deformation monitoring;
  • Atmospheric phase screed estimation techniques;
  • Glacier monitoring;
  • Iceberg drift monitoring;
  • Maritime surveillance;
  • Micro-motion estimation of targets;
  • Terrain surveillance and border monitoring;
  • Data fusion;
  • Space situational awareness (SSA);
  • Satellite debris detection and tracking;
  • Target detection and tracking.

Prof. Thierry Bouwmans
Dr. Filippo Biondi
Dr. Pietro Milillo
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


  • Synthetic Aperture Radar (SAR)
  • Inverse SAR (ISAR)
  • Polarimetric SAR (PolSAR)
  • Interferometric Synthetic Aperture Radar (InSAR)
  • Polarimetric InSAR (PolInSAR)
  • Differential InSAR (DInSAR)
  • 4D SAR Tomography (4D-TomoSAR)
  • Ice and Glaciers monitoring
  • Pixel Tracking
  • Target detection
  • Along-Track SAR Interferometry ATI-SAR
  • Multi Chromatic Analysis (MCA)
  • Doppler Sub-apertures
  • Space situational Awareness (SSA)

Published Papers (2 papers)

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Open AccessArticle
SBAS-InSAR Based Deformation Detection of Urban Land, Created from Mega-Scale Mountain Excavating and Valley Filling in the Loess Plateau: The Case Study of Yan’an City
Remote Sens. 2019, 11(14), 1673; https://doi.org/10.3390/rs11141673 - 14 Jul 2019
Yan’an new district (YND) is one of the largest civil engineering projects for land creation in Loess Plateau, of which the amount of earthwork exceeds 600 million m3, to create 78.5 km2 of flat land. Such mega-scale engineering activities and [...] Read more.
Yan’an new district (YND) is one of the largest civil engineering projects for land creation in Loess Plateau, of which the amount of earthwork exceeds 600 million m3, to create 78.5 km2 of flat land. Such mega-scale engineering activities and complex geological characteristics have induced wide land deformation in the region. Small baseline subset synthetic aperture radar interferometry (SBAS-InSAR) method and 55 Sentinel-1A (S-1A) images were utilized in the present work to investigate the urban surface deformation in the Yan’an urban area and Yan’an new airport (YNA) from 2015 to 2019. The results were validated by the ground leveling measurements in the YNA. It is found that significant uneven surface deformation existed in both YND and YNA areas with maximum accumulative subsidence of 300 and 217 mm, respectively. Moreover, the average subsidence rate of the YND and YNA areas ranged from −70 to 30 mm/year and −50 to 25 mm/year, respectively. The present work shows that the land deformation suffered two periods (from 2015 to 2017 and from 2017 to 2019) and expanded from urban center to surrounding resettlement area, which are highly relevant with urban earthwork process. It is found that more than 60% of land subsidence occurs at filled areas, while more than 65% of surface uplifting occurs at excavation areas. The present work shows that the subsidence originates from the earth filling and the load of urban buildings, while the release of stress is the major factor for the land uplift. Moreover, it is found that the collapsibility of loess and concentrated precipitation deteriorates the degree of local land subsidence. The deformation discovered by this paper shows that the city may suffer a long period of subsidence, and huge challenges may exist in the period of urban maintaining buildings and infrastructure facilities. Full article
(This article belongs to the Special Issue Exploitation of Synthetic Aperture Radar Targets Velocities)
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Open AccessTechnical Note
Micro-Motion Estimation of Maritime Targets Using Pixel Tracking in Cosmo-Skymed Synthetic Aperture Radar Data—An Operative Assessment
Remote Sens. 2019, 11(14), 1637; https://doi.org/10.3390/rs11141637 - 10 Jul 2019
In this paper, we propose a novel strategy to estimate the micro-motion (m-m) of ships from synthetic aperture radar (SAR) images. To this end, observe that the problem of motion and m-m detection of targets is usually solved using synthetic aperture radar (SAR) [...] Read more.
In this paper, we propose a novel strategy to estimate the micro-motion (m-m) of ships from synthetic aperture radar (SAR) images. To this end, observe that the problem of motion and m-m detection of targets is usually solved using synthetic aperture radar (SAR) along-track interferometry through two radars spatially separated by a baseline along the azimuth direction. The approach proposed in this paper for m-m estimation of ships, occupying thousands of pixels, processes the information generated during the coregistration of several re-synthesized time-domain and not overlapped Doppler sub-apertures. Specifically, the SAR products are generated by splitting the raw data according to a temporally small baseline using one single wide-band staring spotlight (ST) SAR image. The predominant vibrational modes of different ships are then estimated. The performance analysis is conducted on one ST SAR image recorded by COSMO-SkyMed satellite system. Finally, the newly proposed approach paves the way for application to the surveillance of land-based industry activities. Full article
(This article belongs to the Special Issue Exploitation of Synthetic Aperture Radar Targets Velocities)
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