scholarly journals Urban Riverway Extraction from High-Resolution SAR Image Based on Blocking Segmentation and Discontinuity Connection

2020 ◽  
Vol 12 (24) ◽  
pp. 4014
Author(s):  
Yu Li ◽  
Yun Yang ◽  
Quanhua Zhao
Keyword(s):  
High Resolution ◽  
Signal To Noise Ratio ◽  
Bottom Layer ◽  
Speckle Reduction ◽  
Image Block ◽  
Sar Images ◽  
The Difference ◽  
Sar Imagery ◽  
Layer Region ◽  
Region Growth

An urban riverway extraction method is proposed for high-resolution synthetic aperture radar (SAR) images. First, the original image is partitioned into overlapping sub-image blocks, in which the sub-image blocks that do not cover riverways are regarded as background. Sub-image blocks covering riverways are then filtered using the iterative adaptive speckle reduction anisotropic diffusion (SRAD) that introduces the relative signal-to-noise ratio (RSNR). The filtered images are segmented quickly by the Sauvola algorithm, and the false riverway fragments are removed by the area and aspect ratio of the connected component in the segmentation results. Using the minimum convex hull of each riverway segment as the connection object, the seeds are automatically determined by the difference between adjacent pyramid layers, and the sub-image block riverway extraction result is used as the bottom layer. The discontinuity connection between river segments is achieved by multi-layer region growth. Finally, the processed sub-image blocks are stitched to get the riverway extraction results for the entire image. To verify the applicability and usefulness of the proposed approach, high-resolution SAR imagery obtained by the Gaofen-3 (GF-3) satellite was used in the assessment. The qualitative and quantitative evaluations of the experimental results show that the proposed method can effectively and completely extract complex urban riverways from high-resolution SAR images.

scholarly journals Onboard Digital Beamformer with Multi-Frequency and Multi-Group Time Delays for High-Resolution Wide-Swath SAR

2021 ◽  
Vol 13 (21) ◽  
pp. 4354
Author(s):  
Wei Xu ◽  
Qi Yu ◽  
Chonghua Fang ◽  
Pingping Huang ◽  
Weixian Tan ◽  
...  
Keyword(s):  
High Resolution ◽  
Time Delays ◽  
Signal To Noise Ratio ◽  
Sar Images ◽  
Digital Beamforming ◽  
Imaging Geometry ◽  
Group Time ◽  
Gain Loss ◽  
Long Pulse ◽  
Wide Swath

Scan-on-receive (SCORE) digital beamforming (DBF) in elevation can significantly improve the signal-to-noise ratio (SNR) and suppress range ambiguities in spaceborne synthetic aperture radar (SAR). It has been identified as one of the important methods to obtain high-resolution wide-swath (HRWS) SAR images. However, with the improvement of geometric resolution and swath width, the residual pulse extension loss (PEL) due to the long pulse duration in the conventional spaceborne onboard DBF processor must be considered and reduced. In this paper, according to the imaging geometry of the spaceborne DBF SAR system, the reason for the large attenuation of the receiving gain at the edge of the wide swath is analyzed, and two improved onboard DBF methods to mitigate the receive gain loss are given and analyzed. Taking account of both the advantages and drawbacks of the two improved DBF methods presented, a novel onboard DBF processor with multi-frequency and multi-group time delays in HRWS SAR is proposed. Compared with the DBF processor only with multi-group time delays, the downlink data rate was clearly reduced, while focusing performance degradation due to phase and amplitude errors between different frequency bands could be mitigated compared with the DBF processor only with multi-frequency time delays. The simulation results of both point and distributed targets validate the proposed DBF processor.

Non-stationary speckle reduction in high resolution SAR images

2018 ◽  
Vol 73 ◽  
pp. 72-82 ◽  
Author(s):  
Zhihuo Xu ◽  
Quan Shi ◽  
Yunjin Chen ◽  
Wensen Feng ◽  
Yeqin Shao ◽  
...  
Keyword(s):  
High Resolution ◽  
Speckle Reduction ◽  
Sar Images

scholarly journals Novel Configurations of Ultrahigh Frequency (≤600 MHz) Analog Frontend for High Resolution Ultrasound Measurement

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2598
Author(s):  
Min Kim ◽  
Jinhyoung Park ◽  
Qifa Zhou ◽  
Koping Shung
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
Signal To Noise Ratio ◽  
Ultrahigh Frequency ◽  
Ultrasound Measurement ◽  
Functional Responses ◽  
Signal To Noise ◽  
Coded Excitation ◽  
Noise Ratio ◽  
The Difference

In this article, an approach to designing and developing an ultrahigh frequency (≤600 MHz) ultrasound analog frontend with Golay coded excitation sequence for high resolution imaging applications is presented. For the purpose of visualizing specific structures or measuring functional responses of micron-sized biological samples, a higher frequency ultrasound is needed to obtain a decent spatial resolution while it lowers the signal-to-noise ratio, the difference in decibels between the signal level and the background noise level, due to the higher attenuation coefficient. In order to enhance the signal-to-noise ratio, conventional approach was to increase the transmit voltage level. However, it may cause damaging the extremely thin piezoelectric material in the ultrahigh frequency range. In this paper, we present a novel design of ultrahigh frequency (≤600 MHz) frontend system capable of performing pseudo Golay coded excitation by configuring four independently operating pulse generators in parallel and the consecutive delayed transmission from each channel. Compared with the conventional monocycle pulse approach, the signal-to-noise ratio of the proposed approach was improved by 7–9 dB without compromising the spatial resolution. The measured axial and lateral resolutions of wire targets were 16.4 µm and 10.6 µm by using 156 MHz 4 bit pseudo Golay coded excitation, respectively and 4.5 µm and 7.7 µm by using 312 MHz 4 bit pseudo Golay coded excitation, respectively.

Building Damage Assessment Using High-Resolution Satellite SAR Images of the 2010 Haiti Earthquake

2016 ◽  
Vol 32 (1) ◽  
pp. 591-610 ◽  
Author(s):  
Hiroyuki Miura ◽  
Saburoh Midorikawa ◽  
Masashi Matsuoka
Keyword(s):  
High Resolution ◽  
Accuracy Assessment ◽  
Building Damage ◽  
Haiti Earthquake ◽  
Sar Images ◽  
Linear Discriminant ◽  
Intensity Images ◽  
Image Pixels ◽  
The Difference ◽  
Collapsed Buildings

Damage to individual buildings in an urban area of Port-au-Prince, Haiti, from the 2010 Haiti earthquake was assessed by means of high-resolution synthetic aperture radar (SAR) intensity images and ancillary building footprints. A comparison of pre- and post-event images and a building damage inventory showed that backscattering intensity between images was more significantly changed in collapsed buildings than in less damaged buildings. The linear discriminant function, based on the difference and correlation coefficient of the images was developed to detect collapsed buildings. The result showed that almost 75% of the buildings were correctly detected by discriminant analysis. An accuracy assessment revealed the difficulty of detecting small and congested buildings because the number of image pixels was too small and the buildings were obscured by neighboring buildings and other features in the images.

scholarly journals BUILDINGS IN HIGH RESOLUTION SAR IMAGES - IDENTIFICATION BASED ON CITYGML DATA

2015 ◽  
Vol II-3/W4 ◽  
pp. 9-16 ◽  
Author(s):  
S. Auer ◽  
A. Donaubauer
Keyword(s):  
High Resolution ◽  
City Center ◽  
Sar Images ◽  
Data Format ◽  
Building Geometry ◽  
First Results ◽  
Automated Processing ◽  
Urban Scene ◽  
System Data ◽  
Sar Imagery

Motivated by the distinct appearance of facades in high resolution SAR images with respect to signal incidence angles and polarizations, this paper introduces a way to fuse SAR imagery and 3D GIS (geoinformation system) data (format: CityGML) based on SAR simulation methods. To this end, the known building geometry is used to simulate the extent of building layover for identifying the related image parts in high resolution TerraSAR-X images. The simulated SAR images are generated and geocoded by an automated processing chain which is initialized by the automated parsing of the CityGML dataset and the TerraSAR-X orbit file. Confirming the functionality of the developed interface between simulation and CityGML, first results are presented for an urban scene in the Munich city center in order to discuss future opportunities in the context of change detection applications.

scholarly journals A Comparative Study of Target Reconstruction of Ultra-High-Resolution CT for Patients with Corona-Virus Disease 2019 (COVID-19)

2020 ◽  
Author(s):  
Shao-mao Lv ◽  
Yu Lin ◽  
Jiang-he Kang ◽  
Shao-yin Duan ◽  
Wei-guo Zhang ◽  
...  
Keyword(s):  
Regression Analysis ◽  
High Resolution ◽  
Blood Vessels ◽  
Virus Disease ◽  
Signal To Noise Ratio ◽  
Ground Glass ◽  
High Resolution Ct ◽  
Interlobular Septum ◽  
Corona Virus ◽  
The Difference

AbstractBackgroundThe corona-virus disease 2019 (COVID-19) pandemic has caused a serious public health risk. Compared with conventional high-resolution CT (C-HRCT, matrix 512), ultra-high resolution CT (U-HRCT, matrix 1024) can increase the effective pixel per unit volume by about 4 times. Our study is to evaluate the value of target reconstruction of U-HRCT in the accurate diagnosis of COVID-19.MethodsA total of 13 COVID-19 cases, 44 cases of other pneumonias, and 6 cases of ground-glass nodules were retrospectively analyzed. The data were categorized into groups A (C-HRCT) and B (U-HRCT), following which iDose4-3 and iDose4-5 were used for target reconstruction, respectively. CT value, noise, and signal-to-noise ratio (SNR) in different reconstructed images were measured. Two senior imaging doctors scored the image quality and the structure of the lesions on a 5-point scale. Chi-square test, variance analysis, and binarylogistic regression analysis were used for statistical analysis.ResultsU-HRCT image can reduce noise and improve SNR with an increase of the iterative reconstruction level. The SNR of U-HRCT image was lower than that of the C-HRCT image of the same iDose4level, and the noise of U-HRCT was higher than that of C-HRCT image; the difference was statistically significant (P< 0.05). Logistic regression analysis showed thatperipleural distribution, thickening of blood vessels and interlobular septum, and crazy-paving pattern were independent indictors of the COVID-19 on U-HRCT. U-HRCT was superior to C-HRCT in showing the blood vessels, bronchial wall, and interlobular septum in the ground-glass opacities; the difference was statistically significant (P < 0.05).ConclusionsPeripleural distribution, thickening of blood vessels and interlobular septum, and crazy-paving pattern on U-HRCT are favorable signs for COVID-19. U-HRCT is superior to C-HRCT in displaying the blood vessels, bronchial walls, and interlobular septum for evaluating COVID-19.

Development of Building Height Data in Peru from High-Resolution SAR Imagery

2014 ◽  
Vol 9 (6) ◽  
pp. 1042-1049 ◽  
Author(s):  
Wen Liu ◽  
◽  
Fumio Yamazaki ◽  
Bruno Adriano ◽  
Erick Mas ◽  
...  
Keyword(s):  
High Resolution ◽  
Satellite Image ◽  
Ground Surface ◽  
Sar Images ◽  
Building Height ◽  
Radar Sensors ◽  
Gis Data ◽  
Building Footprint ◽  
Image Displays ◽  
Sar Imagery

Building data, such as footprint and height, are important information for pre- and post-event damage assessments when natural disasters occur. However, these data are not easily available in many countries. Because of the remarkable improvements in radar sensors, high-resolution (HR) Synthetic Aperture Radar (SAR) images can provide detailed ground surface information. Thus, it is possible to observe a single building using HR SAR images. In this study, a new method is developed to detect building heights automatically from two-dimensional (2D) geographic information system (GIS) data and a single HR TerraSAR-X (TSX) intensity image. A building in a TSX image displays a layover from the actual position to the direction of the sensor, because of the side-looking nature of the SAR. Since the length of the layover on a ground-range SAR image is proportional to the building height, it can be used to estimate this height. We shift the building footprint obtained from 2D GIS data toward the sensor direction. The proposed method was applied to a TSX image of Lima, Peru in the HighSpot mode with a resolution of about 1 m. The results were compared with field survey photos and an optical satellite image, and a reasonable level of accuracy was achieved.

scholarly journals A Bayesian Joint Decorrelation and Despeckling approach for speckle reduction of SAR Images

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
Caifeng Wang ◽  
LinLin Xu ◽  
David Clausi ◽  
Alexander Wong
Keyword(s):  
State Of The Art ◽  
Speckle Noise ◽  
Synthetic Aperture ◽  
Speckle Reduction ◽  
Sar Images ◽  
Novel Approach ◽  
Maximum A Posterior ◽  
Sar Data ◽  
Sar Imagery ◽  
Posterior Estimation

<p>In this paper, we present a novel approach for joint decorrelation<br />and despeckling of synthetic aperture radar (SAR) imagery. An iterative<br />maximum a posterior estimation is performed to obtain the<br />correlation and speckle-free SAR data, which incorporates a correlation<br />model which realistically explores the physical correlated<br />process of speckle noise on signal in SAR imaging. The correlation<br />model is determined automatically via Bayesian estimation in the<br />log-Fourier domain and patch-wise computation is used to account<br />for spatial nonstationarities existing in SAR data. The proposed<br />approach is compared to a state-of-the-art despeckling technique<br />using both simulated and real SAR data. Experimental results illustrate<br />its improvement in preserving the structural detail, especially<br />the sharpness of the edges, when suppressing speckle noise.</p>

Progress in high-resolution CRYO-SEM imaging of viral particles

1996 ◽  
Vol 54 ◽  
pp. 818-819
Author(s):  
Ya Chen ◽  
Geoffrey Letchworth ◽  
John White
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Structural Information ◽  
Signal To Noise Ratio ◽  
Flexible Structures ◽  
Simian Virus ◽  
Topographic Features ◽  
Viral Particles ◽  
Scanning Electron

Low-temperature high-resolution scanning electron microscopy (cryo-HRSEM) has been successfully utilized to image biological macromolecular complexes at nanometer resolution. Recently, imaging of individual viral particles such as reovirus using cryo-HRSEM or simian virus (SIV) using HRSEM, HV-STEM and AFM have been reported. Although conventional electron microscopy (e.g., negative staining, replica, embedding and section), or cryo-TEM technique are widely used in studying of the architectures of viral particles, scanning electron microscopy presents two major advantages. First, secondary electron signal of SEM represents mostly surface topographic features. The topographic details of a biological assembly can be viewed directly and will not be obscured by signals from the opposite surface or from internal structures. Second, SEM may produce high contrast and signal-to-noise ratio images. As a result of this important feature, it is capable of visualizing not only individual virus particles, but also asymmetric or flexible structures. The 2-3 nm resolution obtained using high resolution cryo-SEM made it possible to provide useful surface structural information of macromolecule complexes within cells and tissues. In this study, cryo-HRSEM is utilized to visualize the distribution of glycoproteins of a herpesvirus.

Origin of the alternate bright/dark contrast in HREM images of hexagonal crystals, particularly 6H-SiC

1993 ◽  
Vol 51 ◽  
pp. 914-915
Author(s):  
J.S. Bow ◽  
R.W. Carpenter ◽  
M.J. Kim
Keyword(s):  
High Resolution ◽  
Incident Beam ◽  
Hexagonal Crystal ◽  
Detailed Explanation ◽  
Similar Character ◽  
High Resolution Images ◽  
The Difference ◽  
Zigzag Shape ◽  
Hexagonal Crystals ◽  
Dark Contrast

A prominent characteristic of high-resolution images of 6H-SiC viewed from [110] is a zigzag shape with a period of 6 layers as shown in Fig.1. Sometimes the contrast is same through the 6 layers of (0006) planes (Fig.1a), but in most cases it appears as in Fig.1b -- alternate bright/dark contrast among every three (0006) planes. Alternate bright/dark contrast is most common for the thicker specimens. The SAD patterns of these two types of image are almost same, and there is no indication that the difference results from compositional ordering. O’Keefe et al. concluded this type of alternate contrast was due to crystal tilt in thick parts of the specimen. However, no detailed explanation was given. Images of similar character from Ti3Al, which is also a hexagonal crystal, were reported by Howe et al. Howe attributed the bright/dark contrast among alternate (0002) Ti3Al planes to phase shifts produced by incident beam tilt.

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