Riccardo Lanari

Synthetic aperture radar processing

FUNDAMENTALS Introduction Historical Background Synthetic Aperture Radar Systems Modes Geometric Resolution Goemetric Distortions Synthetic Aperture Radar Signal Statistics InterferometricSynthetic Aperture Radar Phase Statistics Radiometric Resolution Ambiguity Considerations Power and Noise Considerations STRIP MODE TRANSFER FUNCTION Signal Analysis in Time Domain Synthetic Aperture Radar Transfer Function Squinted Geometry Earths Rotation and Sensor Orbit Effects Reflectivity Pattern STRIP MODE DATA PROCESSING Point Target Response Synthetic Aperture Radar Transfer Function and its Approximations Narrow Focus Synthetic Aperture Radar Processing Wide Focus Syntheric Aperture Radar Processing Efficient Wide Focus Synthetic Aperture Radar Processing Range-Doppler Synthetic Aperture Radar Processing Motion Compensation Multiple Look Synthetic Aperture Radar Image Generation Estimation Procedures for Synthetic Aperture Radar Parameters SYNTHETIC APERTURE RADAR INTERFEROMETRY Introduction Interferometric Synthetic Aperture Radar Processing Interferometric Phase Noise Image Registration Techniques Interferometric Phase Statistics Decorrelation Effects Digital Elevation Model Accuracy Phase Unwrapping Weighted Phase Unwrapping Via Finite Element Method Geocoding Differential Interfermetric Synthetic Aperture Radar SCAN MODE SIGNAL ANALYSIS AND DATA PROCESSING Time Domain Analysis Frequency Domain Analysis Point Target Image Generation Scan Mode Data Processing SPOT MODE SIGNAL ANALYSIS AND DATA PROCESSING Time Domain Analysis Frequency Domain Analysis Bandwidths Considerations Residual Video Phase Compensation Spot Mode Image Generation PROCESSING CODE EXAMPLE Code Presentation Processing Code INDEX

A small-baseline approach for investigating deformations on full-resolution differential SAR interferograms

This paper presents a differential synthetic aperture radar (SAR) interferometry (DIFSAR) approach for investigating deformation phenomena on full-resolution DIFSAR interferograms. In particular, our algorithm extends the capability of the small-baseline subset (SBAS) technique that relies on small-baseline DIFSAR interferograms only and is mainly focused on investigating large-scale deformations with spatial resolutions of about 100/spl times/100 m. The proposed technique is implemented by using two different sets of data generated at low (multilook data) and full (single-look data) spatial resolution, respectively. The former is used to identify and estimate, via the conventional SBAS technique, large spatial scale deformation patterns, topographic errors in the available digital elevation model, and possible atmospheric phase artifacts; the latter allows us to detect, on the full-resolution residual phase components, structures highly coherent over time (buildings, rocks, lava, structures, etc.), as well as their height and displacements. In particular, the estimation of the temporal evolution of these local deformations is easily implemented by applying the singular value decomposition technique. The proposed algorithm has been tested with data acquired by the European Remote Sensing satellites relative to the Campania area (Italy) and validated by using geodetic measurements.

On the Extension of the Minimum Cost Flow Algorithm for Phase Unwrapping of Multitemporal Differential SAR Interferograms

In this paper, an extension of the minimum cost flow (MCF) algorithm dealing with a sparse data grid, which allows the unwrapping of multitemporal differential synthetic aperture radar (SAR) interferograms for the generation of deformation time series, is presented. The proposed approach exploits both the spatial characteristics and the temporal relationships among multiple interferograms relevant to a properly chosen sequence. In particular, the presented solution involves two main steps: first of all, for each arc connecting neighboring pixels on the interferometric azimuth/range grid, the unwrapped phase gradients are estimated via the MCF technique applied in the temporal/perpendicular baseline plane. Following this step, these estimates are used as a starting point for the spatial-unwrapping operation implemented again via the MCF approach but carried out in the azimuth/range plane. The presented results, achieved on simulated and real European Remote Sensing satellite SAR data, confirm the effectiveness of the extended MCF unwrapping algorithm

Spotlight SAR data focusing based on a two-step processing approach

The authors present a new spotlight SAR data-focusing algorithm based on a two-step processing strategy that combines the advantages of two commonly adopted processing approaches: the efficiency of SPECAN algorithms and the precision of stripmap focusing techniques. The first step of the proposed algorithm implements a linear and space-invariant azimuth filtering that is carried out via a deramping-based technique representing a simplified version of the SPECAN approach. This operation allows the authors to perform a bulk azimuth raw data compression and to achieve a pixel spacing smaller than (or equal to) the expected azimuth resolution of the fully focused image. Thus, the azimuth spectral folding phenomenon, typically affecting the spotlight data, is overcome, and the space-variant characteristics of the stripmap system transfer function are preserved. Accordingly, the residual and precise focusing of the SAR data is achieved by applying a conventional stripmap processing procedure requiring a minor modification and implemented in the frequency domain. The extension of the proposed technique to the case of high bandwidth transmitted chirp signals is also discussed. Experiments carried out on real and simulated data confirm the validity of the presented approach, which is mainly focused on spaceborne systems.

Generation of digital elevation models by using SIR-C/X-SAR multifrequency two-pass interferometry: the Etna case study

The authors exploit the interferometric multifrequency potentiality of the SIR-C/X-SAR system which is equipped with an L-, C-, and X-band sensor. They present a solution to improve the unwrapping performance of the C- and X-band data by considering the L-band unwrapped pattern. A new algorithm for the generation of a single digital elevation model (DEM) combining L-, C-, and X-band information is presented. This solution is based on the fusion of the unwrapped phase patterns by using a Kalman filter. The proposed fusion operation also accounts for the coherence characteristics of the three data sets. The selected test site is the Mt. Etna region in Italy which is very interesting from the volcanological and geological point of view. Numerical assessments of the achieved results are provided by evaluating the height accuracy with respect to a reference DEM.

Interferometric SAR phase unwrapping using Green's formulation

Any method that permits retrieving full range (unwrapped) phase values starting from their (-/spl pi/,/spl pi/) determination (wrapped phase) can be defined as a phase unwrapping technique. This paper addresses a new procedure for phase unwrapping especially designed for interferometric synthetic aperture radar applications. The proposed algorithm is based on use of Greens first identity. Results on simulated as well as on real data are presented. They both confirm the excellent performance of the procedure.

On the generation of ERS/ENVISAT DInSAR time-series via the SBAS technique

We exploit the small baseline subset (SBAS) algorithm for generating deformation time-series from SAR data acquired by sensors with different characteristics but with the same illumination geometry. In particular, our approach is focused on the use of European Remote Sensing (ERS) and ENVISAT satellite data, the latter acquired by the Advanced Synthetic Aperture Radar sensor on the IS2 swath. The proposed solution is oriented to investigate large-scale displacements with a relatively low spatial resolution (about 100/spl times/100 m) and implements an easy but effective combination of ERS and ENVISAT multilook interferograms which benefits of the temporal overlap between the acquisitions of the two sensors. Moreover, the algorithm does not rely on specific hypothesis on the spatial or temporal characteristics of the investigated deformations. Presented results, achieved on a synthetic aperture radar dataset relevant to the Napoli city area (Italy), confirm the validity of the approach.

Actively growing anticlines beneath catania from the distal motion of Mount Etna's Decollement measured by SAR interferometry and GPS

We used SAR interferometry and GPS to measure the rise of an anticline beneath the urban area of Catania (Italy), which originates from outward thrusting above the basal decollement of Etna volcano. The anticline grows at a rate of over 0.015 m a−1 of SE thrusting and about 0.007 m a−1 of relative uplift. By relating this growth to the simultaneous extension measured at the summit of the volcano, we demonstrate the occurrence of active volcanic spreading. This process may exert a control on eruptions, earthquakes, sector collapses, and landslides.

Deformation and eruptions at Mt. Etna (Italy): A lesson from 15 years of observations

This work was partly funded by INGV and the Italian DPC and was supported by ASI, the Preview Project and CRdC-AMRA. DPC-INGV Flank project providing the funds for the publication fees.

A new method for the compensation of the SAR range cell migration based on the chirp z-transform

Precision synthetic aperture radar (SAR) data processing requires the compensation of the range-dependent range cell migration (RDRCM) phenomenon. This paper describes a new method that permits the compensation of the RDRCM effect using a nonstandard Fourier transform (FT). This operation is applied, in the two-dimensional Fourier domain, to the range signal spectrum and allows the compensation of the azimuth frequency-dependent scaling factor due to the RDRCM. The nonstandard FT is performed via a chirp z-transform that is carried out with one convolution operation and two phase multiplications. >