Resolution Interferometric SAR Research Articles

Automated Extraction of Drainage Channels and Roads through Deep Learning

Abstract. The National Map provides geospatial data that support various uses such as resource management, disaster response, and science investigations. To properly support these needs, data themes of the National Map must be regularly updated and spatially integrated as the features on the ground change because of environmental or man-made events. The elevation theme of the National Map is managed through the 3D Elevation Program (3DEP), which is currently (2019) coordinating collection of high resolution (HR) elevation data for the United States over an eight-year period (Sugarbaker et al. 2014). Through this program, lidar point-cloud data are being collected for the conterminous United States, Hawaii, and U.S. territories, with coarser resolution interferometric synthetic aperture radar (ifsar) data being collected for the remote areas of Alaska. HR digital elevation models (DEMs) can be generated at 1 and 3 meter resolution from the lidar point-cloud data and are also furnished by 3DEP.This research develops automated methods to update the hydrography and transportation themes of the National Map in a manner that integrates with the HR elevation and image layers. Surface water drainage networks can be extracted from a HR DEM using flow-direction and flow-accumulation modelling, but results of these methods vary depending on environmental conditions and the existence of anthropogenic features that may affect the accuracy of the elevation model, such as vegetative cover, roads, bridges, and other urban structures. Hydrologic conditioning or enforcement of a HR DEM overcome some of these issues and improve flow modelling for drainage network extraction through techniques such as filtering (Passalaqua et al. 2010), filling sinks (Tarboton 1997), cutting channels through embankments at culvert and bridge locations (Poppenga et al. 2012), or burning-in existing streams (Maidment 1996). However, drainage network extraction results can vary substantially with these techniques and the methods generally require some manual intervention and/or tuning of parameters (Poppenga et al. 2013). Consequently, additional work is needed to streamline and further automate such methods for the various landscape conditions within the United States.

Shallow Creep Along the 1999 Izmit Earthquake Rupture (Turkey) From GPS and High Temporal Resolution Interferometric Synthetic Aperture Radar Data (2011–2017)

AbstractCharacterizing the spatiotemporal evolution of creep is essential to constrain fault slip budget and understand creep mechanism. Studies based on interferometric synthetic aperture radar and Global Positioning System (GPS) satellite observations until 2012 have shown that the central segment of the 17 August 1999 Mw 7.4 Izmit earthquake on the North Anatolian Fault began slipping aseismically following the event. In the present study, we combine new interferometric synthetic aperture radar time series, based on TerraSAR‐X and Sentinel 1A/B radar images acquired over the period 2011–2017, with near‐field GPS measurement campaigns performed every 6 months from 2014 to 2016. The mean velocity fields reveal that creep on the central segment of the 1999 Izmit fault rupture continues to decay, more than 19 years after the earthquake, in overall agreement with models of postseismic afterslip decaying logarithmically with time for a long period of time. Along the fault section that experienced supershear velocity rupture during the Izmit earthquake creep continues with a rate up to ~ 8 mm/year. A significant transient accelerating creep is detected in December 2016 on the Sentinel‐1 time series, near the maximum creep rate location, associated with a total surface slip of 10 mm released in 1 month only. Additional analyses of the vertical velocity fields show a persistent subsidence on the hanging wall block of the Golcuk normal fault that also ruptured during the Izmit earthquake. Our results demonstrate that afterslip processes along the North Anatolian Fault east‐southeast of Istanbul are more complex than previously proposed as they vary spatiotemporally along the fault.

SAR Interferometry for Sinkhole Early Warning and Susceptibility Assessment along the Dead Sea, Israel

During the past three decades, the Dead Sea (DS) water level has dropped at an average rate of ~1 m/year, resulting in the formation of thousands of sinkholes along its coastline that severely affect the economy and infrastructure of the region. The sinkholes are associated with gradual land subsidence, preceding their collapse by periods ranging from a few days to about five years. We present the results of over six years of systematic high temporal and spatial resolution interferometric synthetic aperture radar (InSAR) observations, incorporated with and refined by detailed Light Detection and Ranging (LiDAR) measurements. The combined data enable the utilization of interferometric pairs with a wide range of spatial baselines to detect minute precursory subsidence before the catastrophic collapse of the sinkholes and to map zones susceptible to future sinkhole formation. We present here four case studies that illustrate the timelines and effectiveness of our methodology as well as its limitations and complementary methodologies used for sinkhole monitoring and hazard assessment. Today, InSAR-derived subsidence maps have become fundamental for sinkhole early warning and mitigation along the DS coast in Israel and are incorporated in all sinkhole potential maps which are mandatory for the planning and licensing of new infrastructure.

Statistical modeling of a joint metric of SAR interferogram's magnitude and phase using Fisher distribution for texture

In this paper, aiming at the precise description of a recently proposed joint metric of SAR interferogram's magnitude and phase (IMP), especially for high resolution interferometric SAR images, a novel distribution denoted as S1 distribution is proposed. At first, under the framework of product model, the Fisher distribution is introduced for modeling the textural component and the closed-form PDF of the novel distribution is presented. The proposed distribution generalizes the existing S0 distribution which models the textural component by the inverse gamma distribution. Then, based on the Mellin transform, a parameter estimator of the proposed model is derived. Finally, the experimental results on real data have validated the efficiency of the proposed distribution and the parameter estimation.

Rapid Estimate and Modeling of Permanent Coseismic Displacements for Large Earthquakes Using High-Rate Global Positioning System Data

Online Material: Figures showing application of fitting window approach, residual displacements and trade‐off curves, and finite fault‐slip models. More and more of the Earth’s active plate boundaries are instrumented with continuous Global Positioning System (cGPS) networks that provide both the earthquake research and response communities with the opportunity to observe coseismic surface deformation in much greater detail and rapidity than was possible a decade ago. These measurements of 3D displacements with high temporal resolution are critical for understanding the kinematics and dynamics of events and are complementary to seismic acceleration observations and high spatial resolution Interferometric Synthetic Aperture Radar observations. In addition, low‐latency GPS has been tested for use in rapid hazard assessment (e.g., Blewitt et al. , 2006, 2009; Allen and Ziv, 2011; Ohta et al. , 2012). CGPS data from dense networks with hundreds to thousands of stations (e.g., GEONET in Japan, EarthScope/PBO in western United States) are now routinely available on a variety of time scales, from daily download to real time. Advances in GPS processing capability enable the estimates of high‐rate (e.g., 5 min, 30 s, 1 Hz or higher) GPS positions very rapidly, even for large networks. As part of the Advanced Rapid Imaging and Analysis (ARIA) team’s response to the M w 9.0 Tohoku‐Oki earthquake, we generated and posted online the first coseismic offset values based on Japan’s dense GEONET cGPS network (Owen et al. , 2011) within 48 hours of the event. These offsets were used in the 26 peer‐reviewed publications that had modeled the Tohoku‐Oki event at the time of this publication. Given the heavy usage of this rapidly available data set for scientific studies, and because many algorithms to model earthquakes are better constrained when they have static coseismic displacements to model the event (in particular in the region of the seismogenic fault …

Geodetic slip rates in the southern San Andreas Fault system: Effects of elastic heterogeneity and fault geometry

We use high resolution interferometric synthetic aperture radar and GPS measurements of crustal motion across the southern San Andreas Fault system to investigate the effects of elastic heterogeneity and fault geometry on inferred slip rates and locking depths. Geodetically measured strain rates are asymmetric with respect to the mapped traces of both the southern San Andreas and San Jacinto faults. Two possibilities have been proposed to explain this observation: large contrasts in crustal rigidity across the faults, or an alternate fault geometry such as a dipping San Andreas fault or a blind segment of the San Jacinto Fault. We evaluate these possibilities using a two‐dimensional elastic model accounting for heterogeneous structure computed from the Southern California Earthquake Center crustal velocity model CVM‐H 6.3. The results demonstrate that moderate variations in elastic properties of the crust do not produce a significant strain rate asymmetry and have only a minor effect on the inferred slip rates. However, we find that small changes in the location of faults at depth can strongly impact the results. Our preferred model includes a San Andreas Fault dipping northeast at 60°, and two active branches of the San Jacinto fault zone. In this case, we infer nearly equal slip rates of 18 ± 1 and 19 ± 2 mm/yr for the San Andreas and San Jacinto fault zones, respectively. These values are in good agreement with geologic measurements representing average slip rates over the last 104–106 years, implying steady long‐term motion on these faults.

Calibration of two‐dimensional floodplain modeling in the central Atchafalaya Basin Floodway System using SAR interferometry

Two‐dimensional (2‐D) satellite imagery has been increasingly employed to improve prediction of floodplain inundation models. However, most focus has been on validation of inundation extent, with little attention on the spatial variations of water elevation and slope. The availability of high resolution Interferometric Synthetic Aperture Radar (InSAR) imagery offers unprecedented opportunity for quantitative validation of surface water heights and slopes derived from 2D hydrodynamic models. In this study, the LISFLOOD‐ACC hydrodynamic model is applied to the central Atchafalaya Basin Floodway System, Louisiana, during high flows typical of spring floods in the Mississippi Delta region, for the purpose of demonstrating the utility of InSAR in 2‐D floodplain model calibration. Two schemes calibrating Manning's roughness in channels and floodplains are compared. First, the model is calibrated in terms of water elevations at a single in situ gage during a 62‐d simulation period from 1 April 2008 to 1 June 2008. Second, the model is calibrated in terms of water elevation changes calculated from ALOS PALSAR 2D imagery acquired on 16 April 2008 and 1 June 2009, an interval of 46 d. The best‐fit model shows that the mean absolute error is 5.7 cm/46 d for InSAR water level calibration. Daily storage changes within the ∼230‐km2 model area are also calculated to be on the order of 107 m3 d−1 during high water of the modeled period. The favorable comparison between both approaches demonstrates the feasibility of SAR interferometry for 2‐D hydrodynamic model calibration and for improved understanding of complex floodplain hydrodynamics.

Water vapour distribution at urban scale using high-resolution numerical weather model and spaceborne SAR interferometric data

Abstract. The local distribution of water vapour in the urban area of Rome has been studied using both a high resolution mesoscale model (MM5) and Earth Remote Sensing-1 (ERS-1) satellite radar data. Interferometric Synthetic Aperture Radar (InSAR) techniques, after the removal of all other geometric effects, estimate excess path length variation between two different SAR acquisitions (Atmospheric Phase Screen: APS). APS are strictly related to the variations of the water vapour content along the radar line of sight. To the aim of assessing the MM5 ability to reproduce the gross features of the Integrated Water Vapour (IWV) spatial distribution, as a first step ECMWF IWV has been used as benchmark against which the high resolution MM5 model and InSAR APS maps have been compared. As a following step, the high resolution IWV MM5 maps have been compared with both InSAR and surface meteorological data. The results show that the high resolution IWV model maps compare well with the InSAR ones. Support to this finding is obtained by semivariogram analysis that clearly shows good agreement beside from a model bias.