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The primary objective of these studies was to quantitatively assess the ground deformation velocities and rates and their natural and man-made controlling factors as the potential risks along the seismically active 70 km section of buried Baku-Tbilisi-Ceyhan Oil, South Caucasus Gas, Western Route Oil and South Caucasus Pipeline Expansion Gas pipelines in Azerbaijan using Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique. PS-InSAR analysis showed that the continuous subsidence was prevailing in the kilometer range of 13-70 of pipelines crossing two active seismic faults. The ground uplift deformations were observed in the pipeline kilometer range of 0-13. The minimum and maximum vertical ground movement velocities were observed to be −21.3 mm/y and 14.1 mm/y along 70 km section of pipelines with 250 m buffer zone. Both of these sites were observed at the range of seismic faults. The spatial distribution of sites with ground deformation velocity less than −15 mm/y and more than 15 mm/y was diverse and random all along 70 km of pipelines without any cumulative spatial patterns. Based on the lower mean, variation and standard deviation of pixel values, the seismic fault in the kilometer range of 21-31 revealed its higher vulnerability to subsidence processes rather than the Seismic Fault in the kilometer range of 46-54. The ground deformation velocities within the range of Seismic Fault KP21-31 revealed the minimum and maximum values of −19.74 mm/y and 14.1 mm/y, respectively whereas at the Seismic Fault KP46-54, the minimum and maximum values were −17.07 mm/y and 9.29 mm/y, respectively. Encouraging level of agreement with the regression coefficients of 0.92 and 0.96 for known subsiding sites at KP28 + 500 and KP52 + 750 and 0.97 and 0.96 for known uplifting sites at KP04 + 900 and KP35 + 050 respectively was observed between the high-precision GPS and PS-InSAR measurements. The diverse spatial distribution and variation of ground movement processes along pipelines demonstrated that general geological and geotechnical understanding of the study area is not sufficient to find and mitigate all the critical sites of subsidence and uplifts for the pipeline operators. The prediction of the potential subsidence or uplift locations based on the field visual verifications holds a lot of uncertainties without broad and detailed scale airborne and satellite space observation technologies. The justification of the budget for the geotechnical maintenance activities along long-range oil and gas pipelines requires sophisticated prioritization and planning of the remediation sites and clear quantitative and qualitative risk assessment proving the activeness of these sites and effectiveness of the remediation measures. This means that the PS-InSAR – based approach outlined in this paper is a significant improvement over current ground-based monitoring practices or can significantly contribute them in the initial phase of risk assessment and prioritization. [ABSTRACT FROM AUTHOR]

The method based on the dual-frequency correlation function of reflected signals is one of the effective approaches for sea wave height estimation in radar altimetry. This method, however, has been applied for relatively low-altitude flights. As shown in our early studies, for the estimation of the sea wave heights using the dual-frequency correlation function, it is necessary to synthesize the array antennas, which are perpendicular to the flight direction. In this paper, we derived the limiting accuracy of the measurement of the sea wave heights using the dual-frequency microwave interferometry, and analyzed its dependence on the sea wave heights and the radar system parameters. Evaluation of the limiting accuracy of the measurement of the sea wave heights shown in the paper verified its high accuracy for sea status monitoring using a small remote sensing spacecraft. [ABSTRACT FROM AUTHOR]

In this article, satellite radar data are analysed to control the deformation of the buildings of Murcia City (SE Spain) affected by subsidence. This phenomenon has occurred as a result of groundwater overexploitation in drought periods, and special attention is paid to the most recent drought which occurred between 2005 and 2008. In the first part of this work, the study area is presented followed by a description of the characteristics and effects of subsidence on the buildings of the urban area. Persistent scatterer interferometry is used to process a satellite base radar dataset measuring the temporal and the spatial evolution of subsidence. These results are analysed with respect to several factors that control subsidence mechanisms: water table decrease, thickness of the compressible layer and the type of foundation of the buildings. To validate these results, a detailed structural damage analysis of several buildings is presented. According to the results presented in this work, it may be concluded that damage of buildings is triggered by soil consolidation due to groundwater overexploitation, demonstrating that the inclusion of this technique can be particularly interesting in structural monitoring framework of civil infrastructures, as a complementary tool to control subsidence damage. [ABSTRACT FROM PUBLISHER]

The investigation here described is aimed at evaluating the actual capability of a Real Aperture Radar (RAR) interferometer to detect the natural vibration of urban buildings solely solicited by wind or environmental noise. The paper shortly reviews some of the most relevant non-contacting measurement techniques that can be employed for ambient vibration testing. Then it introduces the proposed RAR measurement technique. Some experimental results taken from a wide set of observations, carried out through a microwave sensor presently available on the market, are discussed. The main factors affecting the measurability of the vibration amplitude and frequency are singled out. The technique is proved to perform high sensitivity displacement measurements, down to a few microns. [ABSTRACT FROM PUBLISHER]

The geomorphologicalmap is an essential tool to performa proper urban planning inmountainous or hilly areas. In this paper amultidisciplinary approach to derive a 1:2000 geomorphologicalmap is described.The proposedmethodology consists of the integration between aerial photographs, acquired in 2003, and four datasets of Persistent Scatterer Interferometry (PSI) measures to update a pre-existing landslide inventory. The integrated data were used to achieve a validated geomorphological map by means of a geomorphological survey. The study area is located in southern Italy (Agrigento, Sicily). The city of Agrigento, included in the World Heritage List of UNESCO in 1997, is located on the Girgenti hill which is exposed on its northern side, to several landslide phenomena. The top of the hill is characterized by the presence of part of the cultural heritage of the city and is affected by rockfalls, rock topples and shallow-seated landslides, representing a serious risk for important historical buildings. The results demonstrate the validity of this method to achieve a suitable tool in landscape and cultural heritage management. [ABSTRACT FROM AUTHOR]

The prevailing complex geological and ecological conditions of Taiwan have drawn considerable attention from various geo-ecological communities because of their vulnerability to produce various natural hazards at different scales. Located in the tropical/subtropical zone of the Pacific Rim, its ecological and rugged mountainous properties are environmentally sensitive making monitoring and observation especially difficult because of the high population density. In this article, we have investigated the land deformation in two adjacent industrial parks, Jhong-Li and Guei-Shan, in northern Taiwan using radar interferometry. The Interferometric Synthetic Aperture Radar technique for processing a series of data sets was first validated by comparison with ground levelling measurements over a test site. Excellent agreement was obtained in both deformation pattern and magnitude of subsidence rate. The period of observation dated from 1993 to 2000 with Synthetic Aperture Radar images from ERS-1 and ERS-2. The results, after least-squares adjustment, revealed that the maximum subsidence reached 10 cm and the subsidence rates were about 1.8 cm year−1 (at epicentres) since 1993 at both parks. It was also found that the subsidence rate slowed down after 1998 at Jhong-Li park while continuing at Guei-Shan park. This was strongly associated with local groundwater extraction activities. [ABSTRACT FROM AUTHOR]

This research investigates the use of Interferometric Synthetic Aperture Radar (InSAR) to generate a time-series of snow water equivalent (SWE) for dry snow within the Kuparuk watershed, North Slope, Alaska, during the winter of 1993/1994. Maps depicting relative change in phase and the theoretical relative change in SWE between satellite acquisitions are created for 3-day periods at the end of March 1994 using both ascending and descending ERS-1 overpasses. The theoretical coefficient relating relative change in phase and relative change in SWE for C-band is found to be at least twice as large as what is expected when using a simple single-layer snow model for this study area and time period. Without any direct measurements of SWE on the ground, station measurements of snow depth and hourly wind are linked to each 3-day relative change in phase map. Along with a qualitative assessment, quantitative measures of the rate and magnitude of phase change around these stations are directly compared to the hourly wind data for a given 3-day period. InSAR-derived maps acquired around a measured precipitation event show a considerable relationship to the predominant direction of strong winds over each 3-day period while maps acquired around no measureable precipitation depict much less correlation between phase change and predominant direction of strong winds. Despite limited ground measurements to infer snowpack conditions, these results show continued promise for the InSAR technique to measure changes in snowpack conditions (e.g. SWE) at much higher resolutions than manual sampling methods or passive microwave remote sensing. The extension of this technique to current L-band InSAR satellite platforms is also discussed. [ABSTRACT FROM AUTHOR]

Recent progress in radar techniques and systems has led to the development of a microwave interferometer, potentially suitable for non-contact vibration monitoring of civil engineering structures. The main characteristic of the new radar system, named IBIS-S, is the possibility of simultaneously measuring the (static or dynamic) displacement at several points of a structure with high sensitivity. The paper first describes the technical characteristics of the microwave interferometer and the results of laboratory tests carried out to evaluate the actual displacement sensitivity of the equipment. Subsequently, the application of the sensor to the measurement of ambient vibration response on a concrete bridge is presented and discussed. [ABSTRACT FROM AUTHOR]

Space-borne synthetic aperture radar interferometry (INSAR) is a well-known widely used remote sensing technique to get precise (to the millimeter) surface deformation measurements on large areas (thousands of square kilometers) and high spatial density of measurement points (hundreds per square kilometer). A short review of the INSAR basics is dedicated to the readers who are not INSAR specialists. Then, an analysis of the improvement of ground motion measurement offered by multiple repeated space-borne SAR observations gathered by the new generation of satellites is given and compared with ground-based radar results. Examples from Cosmo-SkyMed and TERRASAR-X are shown and compared with C-band or L-band systems. Finally, the impact of the forthcoming C-band satellites like Sentinel 1 A, B is discussed. [ABSTRACT FROM AUTHOR]

Interferometric synthetic aperture radar (InSAR) provides an all-weather imaging capability for measuring ground-surface deformation and inferring changes in land surface characteristics. InSAR enables scientists to monitor and characterize hazards posed by volcanic, seismic, and hydrogeologic processes, by landslides and wildfires, and by human activities such as mining and fluid extraction or injection. Measuring how a volcano's surface deforms before, during, and after eruptions provides essential information about magma dynamics and a basis for mitigating volcanic hazards. Measuring spatial and temporal patterns of surface deformation in seismically active regions is extraordinarily useful for understanding rupture dynamics and estimating seismic risks. Measuring how landslides develop and activate is a prerequisite to minimizing associated hazards. Mapping surface subsidence or uplift related to extraction or injection of fluids during exploitation of groundwater aquifers or petroleum reservoirs provides fundamental data on aquifer or reservoir properties and improves our ability to mitigate undesired consequences. Monitoring dynamic water-level changes in wetlands improves hydrological modeling predictions and the assessment of future flood impacts. In addition, InSAR imagery can provide near-real-time estimates of fire scar extents and fire severity for wildfire management and control. All-weather satellite radar imagery is critical for studying various natural processes and is playing an increasingly important role in understanding and forecasting natural hazards. [ABSTRACT FROM AUTHOR]

The interferometric synthetic aperture radar (InSAR) technique is used to detect surface deformations in the French Nord-Pas-de-Calais coal mining basin. Several subsiding areas had already been observed at the sites of Lens, Billy-Montigny, Courrieres and Ostricourt during the 1992-2000 period. InSAR deformation measurements are compared with ground-based levelling measurements and an analysis of the results shows a good agreement for the relative deformations. However, the InSAR study reveals a systematic bias of the absolute levelling values. Our interpretation is that the stability points of the ground-based monitoring network probably moved during the study period. Such cross-checking is particularly important considering the current legal value of the levelling measurements. [ABSTRACT FROM AUTHOR]

Phase unwrapping is a key step in extracting digital elevation models (DEMs) from interferometric synthetic aperture radar (InSAR) data. A new two-dimensional (2-D) phase unwrapping algorithm based on ant colony optimization (ACO) is proposed, which is used to configure the shortest path linking all residues in an interferogram. Using an optimization strategy to establish the branch cuts, the unwrapping error can be significantly reduced. Simulated and real InSAR image datasets are studied to evaluate the performance of the algorithm. The results of the simulated datasets show that the errors of the algorithm are lower than some conventional methods, and the results from a real InSAR image dataset demonstrate that the ACO approach has no isolated regions in comparison with some conventional approaches. It indicates that our ACO algorithm is an optional compromise strategy between preferable phase unwrapping precision and time-consuming computation. [ABSTRACT FROM AUTHOR]

The reflectance of geological materials to radar waves is used to estimate earth structure in Interferometric Synthetic Aperture Radar (InSAR) and Ground Penetrating Radar. Repeat use over a time window has great potential use in appraising the dynamic behaviour of geological, geotechnical or mining-related structures, such as subsidence profiles. Temporal changes in structure can be masked by temporal changes in physical properties due to changes in vegetative cover or in soil moisture of the reflecting surface overlying the structure of concern. The effect on reflectance of radar waves by seasonal soil moisture variations is demonstrated by numerical modelling using parametric models of soil conductivity and by dielectric/analytic modelling of the plane wave response of a half-space. More elaborate modelling using layered earth or periodic earth is also possible. This study demonstrates that the use of InSAR for subsidence studies is proscribed if soil moisture varies markedly between passes unless the variation in soil moisture can be removed. One technique would involve the use of inverse modelling to estimate the temporal variation of moisture and to correct for it. Inverse mixing bound theory takes an effective dielectric permittivity and uses it to estimate bounds on soil moistures. Testing this on field data represents a possible next step. Another technique would use artificial reflectors to baseline the reflectance of a specified area. [ABSTRACT FROM AUTHOR]

The problem of interferometric SAR (InSAR) image co-registration is addressed. Classical InSAR matching considers only the translation shift between two complex images. However, for accurate radar image matching (different swaths, paths, or aspects angles), other shift parameters would be useful. For two-dimensional images, the application of the Symmetric Phase Only Matching Filtering (SPOMF) to the Fourier-Mellin Invariant (FMI) descriptors allows an accurate and efficient registration of translated, rotated and scaled images. This paper discusses the utility and feasibility of the SPOMF technique on the FMI descriptors of two interferometric SAR images. The FMI-SPOMF technique is applied on different pairs of InSAR data corresponding to areas with different relief types, in France, Nepal and Tunisia. The results are compared with those of classical cross-correlation registration techniques. We find that the FMI-SPOMF descriptors of an interferometric pair of images allows more precise co-registration and moreover could decide on the exploitability of a given interferometric pair. [ABSTRACT FROM AUTHOR]

On 26 December 2003 a 6.5 Mw earthquake took place near the city of Barn, in south-eastern Iran. In order to detect the surface displacement field due to the Barn earthquake, we used satellite sensor images from the new European C-band Envisat Advanced Synthetic Aperture Radar (ASAR). The displacement pattern from InSAR (SAR Interferometry) is well defined. It evidences a north-south high fringe gradient stream located 4km west of the Barn fault. This result represents an important contribution to knowledge of the rupture process of this event and can be useful for improving and revising the interpretations of geological, geodetic and seismological data. [ABSTRACT FROM AUTHOR]

In this paper three different techniques for detecting and quantifying mountain permafrost creep are compared: (1) rock glacier inventory and characterization from in situ indicators, (2) space-borne radar interferometry, and (3) digital processing of repeated airborne imagery. The specific characteristics of the three methods and their complementarity are investigated for the Fletschhorn mountain range in the Simplon/Saas valley region, Swiss Alps. We found that radar interferometry is suitable to quantify the degree of activity and the order of surface velocity of rock glaciers over large areas in one process, with the possibility to also detect very small movements of inactive and relict rock glaciers. On the other hand, aero-photogrammetry represents a valuable base for additional interpretation of the three-dimensional surface flow field (including speed, direction and change in thickness) of the most active rock glaciers. Results from radar interferometry can also form the basis for further detailed in situ investigations. [ABSTRACT FROM AUTHOR]

The coherent combination of several radar images can both improve their resolution and provide accurate geometric information through the technique of radar interferometry. In this paper, we propose a constellation of passive receivers placed around a special elliptical orbit configuration, the interferometric cartwheel, which could fully exploit radar capabilities by using an existing radar satellite as the transmitting source. This orbital configuration ensures a constant interferometric baseline during the entire orbit. The proposed constellation is economical because it is passive. It can be totally independent of the source. For each type of coherent combination, we first review the principle of the measurement, using simple modelling. The principles are adapted for a passive receiver. We introduce the notion of interferometric area to select the orbital configurations. The data processing and management required for the receivers are described. We conclude with examples of constellations and their applications. We show, in particular, that the interferometric cartwheel can easily be used jointly for civilian and defence applications. [ABSTRACT FROM AUTHOR]

Interferometric Synthetic Aperture Radar (InSAR) allows production of high resolution DEM and detection of small earth motions using multiple pass SAR data sets obtained by remote sensing satellite. But the whole process has not yet reached sufficient robustness to warrant automated DEM production as commonly produced by stereovision with optical images. The automatic algorithm for precision registration is one of the bottlenecks in InSAR data processing. In this paper, an automatic approach with multi-step image matching algorithm is presented. All procedures are automatically implemented. The experiment is carried out successfully with SIR-C/L-band InSAR data. The triangular piecewise rectification is also advanced in reducing local distortion between the images and processing the large scene image. The primary result has prospect in the precision registration for the repeat-track InSAR data and reveals the potential of the presented automatic strategy. [ABSTRACT FROM AUTHOR]