Radar Interferometry

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Didier Massonnet - One of the best experts on this subject based on the ideXlab platform.

  • Encyclopedia of Analytical Chemistry - Elevation Modeling and Displacement Mapping using Radar Interferometry
    Encyclopedia of Analytical Chemistry, 2006
    Co-Authors: Didier Massonnet
    Abstract:

    Topographic modeling consists of producing a digital description of the relief of a given area. This description is generally given on a regular grid in two coordinates. The product consists of the value of the altitude of the terrain for each position of the grid, with respect to a reference shape such as an ellipsoid (approximation of the shape of the Earth) or the geoid (shape of the potential of gravity at sea level). The grid itself is defined in a cartographic or a geographic coordinate system. Common systems include the Universal Transverse Mercator (UTM), Lambert or, alternatively, coordinates in latitude/longitude. Topographic data are used in a variety of applications, from the correction of geometric distortion in remote sensing images to the prediction of the volume of materials to be removed in public works. Their applications include military uses, such as collision avoidance for low-flying aircraft or missiles, or civilian ones, such as optimal positioning of transmitters to cover an area for mobile communications. Radar Interferometry is a promising technique for producing topographic maps on a large scale. It makes use of the very peculiar features of the images produced by synthetic aperture Radar (SAR) instruments placed on board satellites. Used in differential mode, this technique can also produce a unique product: the map of the displacements which occur in a given area between two passes by a Radar satellite. Again, the data can be organized as a digital file placed on a grid similar to the ones used for topographic mapping. However, in the case of displacement measurement, the useful piece of data placed on each node is the displacement experienced by the node, expressed in appropriate units of length. As for each new technique, there are a number of points to take care of before interpreting the data. The purpose of this article is to describe the Radar data, both historically and technically, and to detail their two main applications in topography and displacement mapping. The main issues of the interpretation and the availability of the data are covered. Finally, we compare the performance of Radar Interferometry with other techniques, in both domains, and we try to outline its future.

  • Remote Sensing of Active Volcanism - Remote sensing of volcano deformation by Radar Interferometry from various satellites
    Remote Sensing of Active Volcanism, 2000
    Co-Authors: Didier Massonnet, Freysteinn Sigmundsson
    Abstract:

    We describe the remote sensing tool known as satellite Radar Interferometry and its application for measuring crustal deformation at volcanoes, with about 1 cm accuracy. The technique relies on synthetic aperture Radar (SAR) images acquired by Radar satellites at different times. These images are combined into interferograms, which reveal information about the change in range from ground to satellite, expressed as interferometric fringes. We give numerous examples of Radar interferometric applications to volcanology that demonstrate that Interferometry has already been used to measure volcanic deformation throughout the eruptive cycle, using all available spaceborne Radar instruments. Radar Interferometry is an important tool for worldwide volcano monitoring, because basic volcanic phenomena are properly observed, with some caveats, in all climate types, from tropical to sub-polar.

  • Radar Interferometry and its application to changes in the earth s surface
    Reviews of Geophysics, 1998
    Co-Authors: Didier Massonnet, Kurt L Feigl
    Abstract:

    Geophysical applications of Radar Interferometry to measure changes in the Earth's surface have exploded in the early 1990s. This new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture Radar at two distinct times. The resulting interferogram is a contour map of the change in distance between the ground and the Radar instrument. These maps provide an unsurpassed spatial sampling density (∼100 pixels km−2), a competitive precision (∼1 cm), and a useful observation cadence (1 pass month−1). They record movements in the crust, perturbations in the atmosphere, dielectric modifications in the soil, and relief in the topography. They are also sensitive to technical effects, such as relative variations in the Radar's trajectory or variations in its frequency standard. We describe how all these phenomena contribute to an interferogram. Then a practical summary explains the techniques for calculating and manipulating interferograms from various Radar instruments, including the four satellites currently in orbit: ERS-1, ERS-2, JERS-1, and RadarSAT. The next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement: respecting the limits of the technique, assessing its uncertainty, recognizing artifacts, and discriminating different types of signal. We then review the geophysical applications published to date, most of which study deformation related to earthquakes, volcanoes, and glaciers using ERS-1 data. We also show examples of monitoring natural hazards and environmental alterations related to landslides, subsidence, and agriculture. In addition, we consider subtler geophysical signals such as postseismic relaxation, tidal loading of coastal areas, and interseismic strain accumulation. We conclude with our perspectives on the future of Radar Interferometry. The objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it.

  • Readjustment of the Krafla Spreading Segment to crustal rifting measured by satellite Radar Interferometry
    Geophysical Research Letters, 1997
    Co-Authors: Freysteinn Sigmundsson, Helene Vadon, Didier Massonnet
    Abstract:

    Readjustment of the Krafla spreading segment on the Mid-Atlantic Ridge in Iceland, after a rifting episode from 1975 to 1984, is detected by Radar Interferometry. Crustal deformation from 1992 to 1995 is dominated by ∼24 mm/year subsidence above a shallow magma chamber at Krafla, superimposed on ∼7 mm/year along-axis subsidence of the spreading segment relative to its flanks. The deformation is caused by cooling contraction at ∼3 km depth and ductile flow of material away from the spreading axis, at a rate decreasing with time.

  • Reduction of the need for phase unwrapping in Radar Interferometry
    IEEE Transactions on Geoscience and Remote Sensing, 1996
    Co-Authors: Didier Massonnet, Helene Vadon, Marc Rossi
    Abstract:

    Monitoring of a small change by synthetic aperture Radar (SAR) has previously been demonstrated for several sites, We derive two methods for detecting small displacements in the general case of differential Interferometry: (1) the topographic elimination method and (2) the three-pass method. We explain the reasons which make us favor the former method. Validation and calibration of both methods are described. The topographic elimination method is preferred because of the limited need for phase unwrapping. Although phase unwrapping is usually considered to be a key component of Radar Interferometry, we show that it can be avoided most of the time by using a rough digital elevation model available throughout the world and a new technique, the integer interferometric combination (IIC). Several examples validating the IIC technique are presented as well as considerations about the probability and cost of having a successful study on a given site, which is not a site of opportunity. We conclude with some examples of topography-free, map-registered interferograms, which were produced automatically from SAR raw data and digital elevation models of various quality using the above methods. This validates these methods from an operational point of view.

Eric J. Fielding - One of the best experts on this subject based on the ideXlab platform.

  • Triggered slip: Observations of the 17 August 1999 Izmit (Turkey) earthquake using Radar Interferometry
    Geophysical Research Letters, 2001
    Co-Authors: T Wright, Eric J. Fielding, B. Parsons
    Abstract:

    We use Synthetic Aperture Radar Interferometry (InSAR) to map the\ndisplacement field of the 17 August 1999 Izmit earthquake, which\nlargely conforms to that predicted for an elastic upper crust. We\ndetermine the earthquake source parameters and show that slip continues\nfarther west than the mapped fault ruptures. We also show that additional\nsub-surface displacements occurred on parallel strands of the North\nAnatolian Fault Zone. We argue that this was caused by changes in\nstatic stress accompanying the mainshock, or by the dynamic release\nof regional stresses.

  • synthetic aperture Radar Interferometry to measure earth s surface topography and its deformation
    Annual Review of Earth and Planetary Sciences, 2000
    Co-Authors: Roland Burgmann, Paul A Rosen, Eric J. Fielding
    Abstract:

    Synthetic aperture Radar Interferometry (InSAR) from Earth-orbiting spacecraft provides a new tool to map global topography and deformation of the Earth's surface. Radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter-scale accuracy. These data sets aid in the analysis and interpretation of tectonic and volcanic landscapes. If the Earth's surface deformed between two Radar image acquisitions, a map of the surface dis- placement with tens-of-meters resolution and subcentimeter accuracy can be con- structed. This review gives a basic overview of InSAR for Earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of InSAR for mapping the topography and deformation of the Earth.

Sean Buckley - One of the best experts on this subject based on the ideXlab platform.

  • Assessing Collapse Risk in Evaporite Sinkhole-prone Areas Using Microgravimetry and Radar Interferometry
    Journal of Environmental & Engineering Geophysics, 2012
    Co-Authors: Jeffrey G. Paine, Sean Buckley, Edward W. Collins, Clark R. Wilson
    Abstract:

    Geophysical and remote-sensing methods were applied to better understand sinkhole precursor movement and assess the potential for sinkhole development in evaporitic areas. The approach is illustrated with two examples over bedded salt deposits and a salt dome in Texas, USA. Large sinkholes (90 to 200 m in diameter) formed over Permian bedded salt near Wink in western Texas in June 1980 and May 2002, and on the flank of a coastal-plain salt dome in Daisetta in May 2008. Residents, government officials, and industry representatives wish to better understand the potential for sinkhole formation and growth in both areas. At Wink, limited spatial and temporal data on vertical ground movement from standard surveying has been greatly extended by satellite-based Radar Interferometry, which was used to delineate areas having recent movement and determine rates of movement. Results from Interferometry guided site-specific investigations that included acquisition of high-resolution gravity data, which identified shallow-source mass deficits that indicate potential for continued subsidence or sinkhole formation. At Daisetta, Interferometry was used to determine that no detectable subsidence preceded sinkhole collapse (indicating sudden collapse once the upward-migrating void reached a depth that allowed the cohesiveness of overlying semiconsolidated sediments to be overcome), and gravimetry was used to identify other areas where shallow mass deficits exist across the salt dome. Data from both areas can be used to construct risk maps, design comprehensive subsurface investigations, and develop monitoring programs based on repeat Radar Interferometry and geodetic GPS measurements.

  • ASSESSING SINKHOLE POTENTIAL AT WINK AND DAISETTA, TEXAS USING GRAVIMETRY AND Radar Interferometry
    22nd EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems, 2009
    Co-Authors: Jeffrey G. Paine, Sean Buckley, Edward W. Collins, Clark R. Wilson, Wade Kress
    Abstract:

    Large sinkholes (50 to 200 m in diameter) formed over Permian bedded salt near Wink in western Texas in June 1980 and May 2002 and on the flank of a salt dome at Daisetta, Texas in May 2008. Residents, government officials, and industry representatives would like to better understand the potential for sinkhole formation and growth. We are applying several geophysical methods to better understand sinkhole precursors and assess the potential for future sinkhole development. At Wink, limited data on vertical ground movement from standard surveying has been greatly extended by satellite-based Radar Interferometry, which we are using to delineate areas having recent movement and determine rates of movement. Results from Interferometry are guiding acquisition of high-resolution gravity data, which has identified shallow-source mass deficits that indicate potential for continued subsidence or sinkhole formation. At Daisetta, we are using Interferometry to determine whether vertical movement preceded sinkhole collapse and gravimetry to identify areas where shallow mass deficits exist across the salt dome. These initial data are helping to design a more comprehensive subsurface investigation and develop a monitoring program based on Radar Interferometry and geodetic GPS measurements.

  • land subsidence in houston texas measured by Radar Interferometry and constrained by extensometers
    Journal of Geophysical Research, 2003
    Co-Authors: Sean Buckley, Scott Hensley, Paul A Rosen, Byron D Tapley
    Abstract:

    [1] We present results from a Radar Interferometry study over the Houston-Galveston, Texas Gulf Coast region. From the nearly 60 potential interferograms considered, an atmospheric artifact assessment is performed and a tractable set of interferograms selected for detailed processing and error analysis. The subsequent interferogram time series spanning 1996–1998 is constrained by coincident extensometer data with root-mean-square error less than 2.5 mm. The interferogram time series confirms that historic subsidence in east Houston has stopped. Consistent with current groundwater use patterns, broad-scale subsidence bowls are observed in west and northwest Houston, where maximum subsidence rates are in excess of 2 and 4 cm yr−1, respectively. Linear interferogram phase signatures associated with approximately 1 cm of differential subsidence across faults, including the Long Point fault in northwest Houston, are observed. Near the Seabrook extensometer, a hereto-unidentified subsidence bowl with a maximum subsidence rate in excess of 3 cm yr−1 is revealed. This study demonstrates that when used in conjunction with a set of traditional geodetic measurements, Radar Interferometry can measure the spatial and temporal evolution of urban land subsidence within even the most challenging of environments.

Ian Joughin - One of the best experts on this subject based on the ideXlab platform.

  • synthetic aperture Radar Interferometry
    Proceedings of the IEEE, 2000
    Co-Authors: P A Rosen, Scott Hensley, Ian Joughin, F K Li, S N Madsen, Ernesto Rodriguez, Richard M. Goldstein
    Abstract:

    Synthetic aperture Radar Interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristic of the surface. By exploiting the phase of the coherent Radar signal, Interferometry has transformed Radar remote sensing from a largely interpretive science to a quantitative tool, with applications in cartography, geodesy, land cover characterization, and natural hazards. This paper reviews the techniques of Interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.

  • A Mini-Surge on the Ryder Glacier, Greenland, Observed by Satellite Radar Interferometry
    Science, 1996
    Co-Authors: Ian Joughin, S. Tulaczyk, Mark Fahnestock, Ron Kwok
    Abstract:

    Satellite Radar Interferometry reveals that the speed of the Ryder Glacier increased roughly threefold and then returned to normal (100 to 500 meters/year) over a 7-week period near the end of the 1995 melt season. The accelerated flow represents a substantial, though short-lived, change in ice discharge. During the period of rapid motion, meltwater-filled supraglacial lakes may have drained, which could have increased basal water pressure and caused the mini-surge. There are too few velocity measurements on other large outlet glaciers to determine whether this type of event is a widespread phenomenon in Greenland, but because most other outlet glaciers are at lower latitudes, they should experience more extensive melting, making them more susceptible to meltwater-induced surges.

  • measurement of ice sheet topography using satellite Radar Interferometry
    Journal of Glaciology, 1996
    Co-Authors: Ian Joughin, R. Kwok, Mark Fahnestock, Dale P Winebrenner, William B. Krabill
    Abstract:

    Detailed digital elevation models (DEMs) do not exist for much of the Greenland and Antarctic ice sheets. Radar altimetry is at present the primary, in many cases the only, source of topographic data over the ice sheets, but the horizontal resolution of such data is coarse. Satellite-Radar Interferometry uses the phase difference between pairs of synthetic aperture Radar (SAR) images to measure both ice-sheet topography and surface displacement. We have applied this technique using ERS-1 SAR data to make detailed (i.e. 80 m horizontal resolution) maps of surface topography in a 100 km by 300 km strip in West Greenland. extending northward from just above Jakobshavns Isbrae. Comparison with a 76 km long line of airborne laser-altimeter data shows that we have achieved a relative accuracy of 2.5m along the profile. These observations provide a detailed view of dynamically supported topography near the margin of an ice sheet. In the final section we compare our estimate of topography with phase contours due to motion, and confirm our earlier analysis concerning vertical ice-sheet motion and complexity in ERS-1 SAR interferograms.

Scott Hensley - One of the best experts on this subject based on the ideXlab platform.

  • Radar Interferometry
    2008 IEEE Radar Conference, 2008
    Co-Authors: Scott Hensley
    Abstract:

    Since its inception 30 years ago perhaps no innovation in Radar technology has made such a tremendous impact on the field as that of Radar Interferometry. Radar Interferometry uses two or more observations separated in either time or space to measure fraction of a wavelength scale range differences between the two observations. Radar Interferometry is used by scientific, commercial and government institutions for numerous applications including topographic map generation, surface deformation mapping, landslide monitoring, current velocity measurement, vegetation structure determination and change detection. Radar interferometers can be flown on either spaceborne or airborne platforms or be fixed observing systems. This course is designed to provide an overview of the basic concepts of Radar Interferometry and an introduction to some of its applications. The course will cover basic Radar imaging principles, a geometric and imaging signal perspective of the interferometric phase, interferometric correlation, basic sensitivity equations, phase unwrapping, topographic mapping and repeat pass Interferometry for deformation measurements. The principles will be illustrated with examples from both spaceborne and airborne interferometric data sets. An overview of some of the major applications of Radar Interferometry will be presented with an emphasis on topographic and deformation mapping. The course will also briefly touch upon permanent scatter methods and polarimetric Interferometry.

  • land subsidence in houston texas measured by Radar Interferometry and constrained by extensometers
    Journal of Geophysical Research, 2003
    Co-Authors: Sean Buckley, Scott Hensley, Paul A Rosen, Byron D Tapley
    Abstract:

    [1] We present results from a Radar Interferometry study over the Houston-Galveston, Texas Gulf Coast region. From the nearly 60 potential interferograms considered, an atmospheric artifact assessment is performed and a tractable set of interferograms selected for detailed processing and error analysis. The subsequent interferogram time series spanning 1996–1998 is constrained by coincident extensometer data with root-mean-square error less than 2.5 mm. The interferogram time series confirms that historic subsidence in east Houston has stopped. Consistent with current groundwater use patterns, broad-scale subsidence bowls are observed in west and northwest Houston, where maximum subsidence rates are in excess of 2 and 4 cm yr−1, respectively. Linear interferogram phase signatures associated with approximately 1 cm of differential subsidence across faults, including the Long Point fault in northwest Houston, are observed. Near the Seabrook extensometer, a hereto-unidentified subsidence bowl with a maximum subsidence rate in excess of 3 cm yr−1 is revealed. This study demonstrates that when used in conjunction with a set of traditional geodetic measurements, Radar Interferometry can measure the spatial and temporal evolution of urban land subsidence within even the most challenging of environments.

  • synthetic aperture Radar Interferometry
    Proceedings of the IEEE, 2000
    Co-Authors: P A Rosen, Scott Hensley, Ian Joughin, F K Li, S N Madsen, Ernesto Rodriguez, Richard M. Goldstein
    Abstract:

    Synthetic aperture Radar Interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristic of the surface. By exploiting the phase of the coherent Radar signal, Interferometry has transformed Radar remote sensing from a largely interpretive science to a quantitative tool, with applications in cartography, geodesy, land cover characterization, and natural hazards. This paper reviews the techniques of Interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.