scholarly journals Generation of Complete SAR Geometric Distortion Maps Based on DEM and Neighbor Gradient Algorithm

2018 ◽  
Vol 8 (11) ◽  
pp. 2206 ◽  
Author(s):  
Xiaohong Chen ◽  
Qian Sun ◽  
Jun Hu
Keyword(s):  
Synthetic Aperture Radar ◽  
Negative Impact ◽  
Gradient Algorithm ◽  
Synthetic Aperture ◽  
Geometric Distortion ◽  
Landslide Monitoring ◽  
Mountainous Area ◽  
Geometric Distortions ◽  
Elevation Model ◽  
Aperture Radar

Radar-specific imaging geometric distortions (including foreshortening, layover, and shadow) that occur in synthetic aperture radar (SAR) images acquired over mountainous areas have a negative impact on the suitability of the interferometric SAR (InSAR) technique to monitor landslides. To address this issue, many distortion simulation methods have been presented to predict the areas in which distortions will occur before processing the SAR image. However, the layover and shadow regions are constituted by active as well as passive subregions. Since passive distortions are caused by active distortions and can occur in the flat area, it is difficult to distinguish the transition zone between passive distortion and non-distortion areas. In addition, passive distortion could cover part of the foreshortening or active layover/shadow areas but has generally been ignored. Therefore, failure to simulate passive distortion leads to incomplete simulated distortions. In this paper, an algorithm to define complete SAR geometric distortions and correct the boundaries among different distortions is presented based on the neighbor gradient between the passive and active distortions. It is an image-processing routine applied to a digital elevation model (DEM) of the terrain to be imaged by the available SAR data. The performance of the proposed method has been validated by the ascending and descending Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) images acquired over the Chongqing mountainous area of China. Through the investigation of passive distortion, we can have a deeper understanding of the formation and characteristics of these distortions. Moreover, it provides very meaningful information for research on areas such as landslide monitoring.

scholarly journals GEOREFERENCING ON SYNTHETIC APERTURE RADAR IMAGERY

2015 ◽  
Vol XL-1-W5 ◽  
pp. 179-184
Author(s):  
M. Esmaeilzade ◽  
J. Amini ◽  
S. Zakeri
Keyword(s):  
Synthetic Aperture Radar ◽  
Digital Elevation Model ◽  
Synthetic Aperture ◽  
Geometric Distortion ◽  
Original Image ◽  
Sar Images ◽  
Geometric Distortions ◽  
Digital Elevation ◽  
Elevation Model ◽  
Aperture Radar

Due to the SAR<sup>1</sup> geometry imaging, SAR images include geometric distortions that would be erroneous image information and the images should be geometrically calibrated. As the radar systems are side looking, geometric distortion such as shadow, foreshortening and layover are occurred. To compensate these geometric distortions, information about sensor position, imaging geometry and target altitude from ellipsoid should be available. In this paper, a method for geometric calibration of SAR images is proposed. The method uses Range-Doppler equations. In this method, for the image georeferencing, the DEM<sup>2</sup> of SRTM with 30m pixel size is used and also exact ephemeris data of the sensor is required. In the algorithm proposed in this paper, first digital elevation model transmit to range and azimuth direction. By applying this process, errors caused by topography such as foreshortening and layover are removed in the transferred DEM. Then, the position of the corners on original image is found base on the transferred DEM. Next, original image registered to transfer DEM by 8 parameters projective transformation. The output is the georeferenced image that its geometric distortions are removed. The advantage of the method described in this article is that it does not require any control point as well as the need to attitude and rotational parameters of the sensor. Since the ground range resolution of used images are about 30m, the geocoded images using the method described in this paper have an accuracy about 20m (subpixel) in planimetry and about 30m in altimetry. <br><br> <sup>1</sup> Synthetic Aperture Radar <br> <sup>2</sup> Digital Elevation Model

scholarly journals An Improved R-Index Model for Terrain Visibility Analysis for Landslide Monitoring with InSAR

2021 ◽  
Vol 13 (10) ◽  
pp. 1938
Author(s):  
Tianhe Ren ◽  
Wenping Gong ◽  
Victor Mwango Bowa ◽  
Huiming Tang ◽  
Jun Chen ◽  
...  
Keyword(s):  
Synthetic Aperture Radar ◽  
Poor Performance ◽  
Synthetic Aperture ◽  
Landslide Monitoring ◽  
Sar Images ◽  
Index Model ◽  
Digital Elevation ◽  
Terrain Effect ◽  
Elevation Model ◽  
Aperture Radar

The interferometric synthetic aperture radar (InSAR) technique is widely adopted for detecting and monitoring landslides, but its effectiveness is often degraded in mountainous terrains, due to geometric distortions in the synthetic aperture radar (SAR) image input. To evaluate the terrain effect on the applicability of InSAR in landslide monitoring, a variety of visibility evaluation models have been developed, among which the R-index models are quite popular. In consideration of the poor performance of the existing R-index models in the passive layover region, this study presents an improved R-index model, in which a coefficient for improving the visibility evaluation in the far passive layover regions is incorporated. To demonstrate the applicability of the improved R-index model, the terrain visibility of SAR images in Fengjie, a county in the Three Gorges Reservoirs region, China, is studied. The effectiveness of the improved R-index model is demonstrated through comparing the visibility evaluation results with those obtained from the existing R-index models and P-NG method. Further, the effects of the line-of-sight (LOS) parameters of SAR images and the resolution of the digital elevation model (DEM) on the terrain visibility are discussed.

scholarly journals Data Correction Method of The Persistent Scatterer Interferometric Synthetic Aperture Radar Technique in Landslide Surface Monitoring

Mining Scince ◽  
2019 ◽  
Vol 26 ◽  
Author(s):  
Mowen Xie ◽  
Fuxia Lv ◽  
Liwei Wang
Keyword(s):  
Synthetic Aperture Radar ◽  
Single Point ◽  
Synthetic Aperture ◽  
Hydropower Station ◽  
Landslide Monitoring ◽  
Interferometric Synthetic Aperture Radar ◽  
Reservoir Area ◽  
Radar Technique ◽  
Aperture Radar

Landslides generally cause more damage than first predicted. Currently, many methods are available for monitoring landslides occurrence. Conventional methods are mainly based on single-point monitoring, which omits the aspect of variation in large-scale landslides. Due to the development of radar satellites, the differential interferometric synthetic aperture radar technique has been widely used for landslide monitoring. In this study, an experimental region in the Wudongde Hydropower Station reservoir area was studied using archived spaceborne synthetic aperture radar (SAR) data collected over many years. As the permanent scatterer interferometric SAR (PS-InSAR) technique is an advanced technology, it could be suitably used to overcome the time discontinuity in long time series. However, the accuracy of date processing obtained using the PS-InSAR technique is lower than that obtained using the single-point monitoring method. The monitoring results of the PS-InSAR technique only demonstrate the moving trend of landslides and do not present the actual displacement. The Advanced Land Observation Satellite and a high-precision total station were used for long-term landslide monitoring of the Jinpingzi landslide at the Wudongde Hydropower Station reservoir area. Based on a relationship analysis between the data obtained using the PS-InSAR technique and the total station, a revised method was proposed to reduce the errors in the PS-InSAR monitoring results. The method can not only enhance the monitoring precision of the PS-InSAR technology but also achieve long-term monitoring of landslide displacement from a bird’s-eye view.

scholarly journals Simulation of Three-Dimensional of coastal erosion using differential interferometric synthetic aperture radar

2013 ◽  
Vol 16 (1) ◽  
pp. 80-86
Keyword(s):  
Synthetic Aperture Radar ◽  
Three Dimensional ◽  
Shoreline Change ◽  
Synthetic Aperture ◽  
Interferometric Synthetic Aperture Radar ◽  
Envisat Asar ◽  
Digital Elevation ◽  
Elevation Model ◽  
Dimensional Object ◽  
Aperture Radar

<p>This study aims at modelling three-dimensional shoreline change rates using differential interferometric synthetic aperture radar (DInSAR) techinuqe. Neverthless, decorrelation plays significant role to control the accuracy of three dimensional object reconstruction using DInSAR. To solve this problem, multichannel MAP height estimator algorithm is implemented with in ENVISAT ASAR data. Therefore, the proposed method has been applied to coastaline of Johor, Malaysia. The study shows the critical erosion of -3.5 m y-1 with accuracy (RMSE) of &plusmn;0.05 m. In addition, the volume rate of shoreline changes of -2343.42 m3 y-1 corresponds to the lowest digital elevation model (DEM) of 7.4 m. It can be said that accurate rate of shoreline change can be achieved with root mean square error (RMSE) of &plusmn;0.05 m using multichannel MAP height estimator algorithm.</p>

Glacier displacement on Comfortlessbreen, Svalbard, using 2-pass differential SAR interferometry (DInSAR) with a digital elevation model

Polar Record ◽  
2011 ◽  
Vol 48 (1) ◽  
pp. 17-25 ◽  
Author(s):  
Nora Jennifer Schneevoigt ◽  
Monica Sund ◽  
Wiley Bogren ◽  
Andreas Kääb ◽  
Dan Johan Weydahl
Keyword(s):  
Synthetic Aperture Radar ◽  
Digital Elevation Model ◽  
Sar Interferometry ◽  
Synthetic Aperture ◽  
Synthetic Aperture Radar Interferometry ◽  
Glacier Terminus ◽  
Digital Elevation ◽  
Reference Images ◽  
Elevation Model ◽  
Aperture Radar

ABSTRACTDifferential synthetic aperture radar interferometry (DInSAR) exploits the coherence between the phases of two or more satellite synthetic aperture radar (SAR) scenes taken from the same orbit to separate the phase contributions from topography and movement by subtracting either phase. Hence pure terrain displacement can be derived without residual height information in it, but only the component of movement in line-of-sight direction is represented in a differential interferogram. Comfortlessbreen, a recently surging glacier, flows predominantly in this direction with respect to the European Remote Sensing satellites ERS-1 and ERS-2. Four C-band SAR scenes from spring 1996 were selected because of the high coherence between the respective pairs of the 1-day repeat-pass tandem mission of the ERS sensors. 2-pass DInSAR is performed in combination with a SPOT5 (Satéllite pour l'Observation de la Terre 5) SPIRIT (SPOT5 stereoscopic survey of Polar Ice: Reference Images and Topography) digital elevation model (DEM) from 2007. The different processing steps and intermediate image products, including unwrapping and generation of displacement maps, are detailed in order to convey the DInSAR processing chain to the beginner in the field of interferometry. Maximum horizontal displacements of 18 to 20 cm d−1 in ground range direction can be detected at the glacier terminus, while a few centimetres per day characterised most of the middle and upper portions of Comfortlessbreen in spring 1996.

scholarly journals Surge-related topographic change of the glacier Sortebræ, East Greenland, derived from synthetic aperture radar interferometry

2003 ◽  
Vol 49 (166) ◽  
pp. 381-390 ◽  
Author(s):  
Hamish Pritchard ◽  
Tavi Murray ◽  
Tazio Strozzi ◽  
Stuart Barr ◽  
Adrian Luckman
Keyword(s):  
Synthetic Aperture Radar ◽  
Radar Interferometry ◽  
Synthetic Aperture ◽  
East Greenland ◽  
Synthetic Aperture Radar Interferometry ◽  
Vertical Error ◽  
Elevation Model ◽  
Map Data ◽  
The Impact ◽  
Aperture Radar

AbstractA major surge of the glacier complex of Sortebræ, East Greenland, occurred between 1992 and 1995. The impact of this surge on the topography of Sortebræ was examined through the production of a pre-surge (1981) digital elevation model (DEM) from interpolated digital map data, and a post-surge DEM from differential synthetic aperture radar interferometry using European Remote-sensing Satellite (ERS) imagery. The combined vertical error is typically 30–40 m; however, downdraw of up to 270 m in the reservoir zone, and uplift of up to 145 m in the receiving zone were measured. The upper glacier reservoir area discharged in excess of 24.3 ± 9.5 km3 volume over the surge, of which ∼12.5 km3 was stored in the advanced lower glacier, the balance being lost, predominantly to calving.

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