Bistatic-ISAR cross-range scaling and distortion correction

2021 ◽  
Author(s):  
Likang Deng ◽  
Shuanghui Zhang ◽  
Yongxiang Liu
Keyword(s):  
Distortion Correction

SPECTRA: A program for processing electron images of crystals

1992 ◽  
Vol 50 (1) ◽  
pp. 132-133
Author(s):  
M.F. Schmid ◽  
R. Dargahi ◽  
M. W. Tam
Keyword(s):  
Lattice Distortion ◽  
Data Transfer ◽  
Reciprocal Lattice ◽  
Data Entry ◽  
Image Data ◽  
Distortion Correction ◽  
Specimen Preparation ◽  
Electron Image ◽  
Computer Controlled ◽  
Program Modules

Electron crystallography is an emerging field for structure determination as evidenced by a number of membrane proteins that have been solved to near-atomic resolution. Advances in specimen preparation and in data acquisition with a 400kV microscope by computer controlled spot scanning mean that our ability to record electron image data will outstrip our capacity to analyze it. The computed fourier transform of these images must be processed in order to provide a direct measurement of amplitudes and phases needed for 3-D reconstruction.In anticipation of this processing bottleneck, we have written a program that incorporates a menu-and mouse-driven procedure for auto-indexing and refining the reciprocal lattice parameters in the computed transform from an image of a crystal. It is linked to subsequent steps of image processing by a system of data bases and spawned child processes; data transfer between different program modules no longer requires manual data entry. The progress of the reciprocal lattice refinement is monitored visually and quantitatively. If desired, the processing is carried through the lattice distortion correction (unbending) steps automatically.

scholarly journals A Tree Ring Measurement Method Based on Error Correction in Digital Image of Stem Analysis Disk

Forests ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 464
Author(s):  
Wenjie Zhang ◽  
Tianzhong Zhao ◽  
Xiaohui Su ◽  
Baoguo Wu ◽  
Zhiqiang Min ◽  
...  
Keyword(s):  
Error Correction ◽  
Tree Ring ◽  
Tree Rings ◽  
Digital Image ◽  
Regression Equation ◽  
Distortion Correction ◽  
Geometric Distortion ◽  
Stem Analysis ◽  
Correction Model ◽  
Ring Radius

Stem analysis is an essential aspect in forestry investigation and forest management, as it is a primary method to study the growth law of trees. Stem analysis requires measuring the width and number of tree rings to ensure the accurate measurement, expand applicable tree species, and reduce operation cost. This study explores the use of Open Source Computer Vision Library (Open CV) to measure the ring radius of analytic wood disk digital images, and establish a regression equation of ring radius based on image geometric distortion correction. Here, a digital camera was used to photograph the stem disks’ tree rings to obtain digital images. The images were preprocessed with Open CV to measure the disk’s annual ring radius. The error correction model based on the least-square polynomial fitting method was established for digital image geometric distortion correction. Finally, a regression equation for tree ring radius based on the error correction model was established. Through the above steps, click the intersection point between the radius line and each ring to get the pixel distance from the ring to the pith, then the size of ring radius can be calculated by the regression equation of ring radius. The study’s method was used to measure the digital image of the Chinese fir stem disk and compare it with the actual value. The results showed that the maximum error of this method was 0.15 cm, the average error was 0.04 cm, and the average detection accuracy reached 99.34%, which met the requirements for measuring the tree ring radius by stem disk analysis. This method is simple, accurate, and suitable for coniferous and broad-leaved species, which allows researchers to analyze tree ring radius measurement, and is of great significance for analyzing the tree growth process.

scholarly journals Correcting for Static Shift of Magnetotelluric Data with Airborne Electromagnetic Measurements: A Case Study from Rathlin Basin, Northern Ireland

2016 ◽  
Author(s):  
Robert Delhaye ◽  
Volker Rath ◽  
Alan G. Jones ◽  
Mark R. Muller ◽  
Derek Reay
Keyword(s):  
Distortion Correction ◽  
Vertical Scaling ◽  
Spatial Density ◽  
Target Area ◽  
Resistivity Structure ◽  
Static Shift ◽  
Magnetotelluric Data ◽  
Archie’S Law ◽  
Order Of Magnitude ◽  
Resistivity Variation

Abstract. Galvanic distortions of magnetotelluric (MT) data, such as the static shift effect, are a known problem that can lead to incorrect estimation of resistivities and erroneous modelling of geometries with resulting misinterpretation of subsurface electrical resistivity structure. A wide variety of approaches have been proposed to account for these galvanic distortions, some depending on the target area, with varying degrees of success. The natural laboratory for our study is a hydraulically permeable volume of conductive sediment at depth, the internal resistivity structure of which can be used to estimate reservoir viability for geothermal purposes, however static shift correction is required in order to ensure robust and precise modelling accuracy. We propose a method employing frequency–domain electromagnetic data for static shift correction, which in our case are regionally available with high spatial density. The spatial distributions of the derived static shift corrections are analysed and applied to the uncorrected MT data prior to inversion. Two comparative inversion models are derived, one with and one without static shift corrections, with instructive results. As expected from the one–dimensional analogy of static shift correction, at shallow model depths, where the structure is controlled by a single local MT site, the correction of static shift effects leads to vertical scaling of resistivity-thickness products in the model, with the corrected model showing improved correlation to existing borehole wireline resistivity data. In turn, as these vertical scalings are effectively independent of adjacent sites, lateral resistivity distributions are also affected, with up to half a decade of resistivity variation between the models estimated at depths down to 2000 m. Simple estimation of differences in bulk porosity, derived using Archie’s Law, between the two models reinforces our conclusion that the sub–order of magnitude resistivity contrasts induced by correction of static shifts correspond to similar contrasts in estimated porosities, and hence, for purposes of reservoir investigation or similar cases requiring accurate absolute resistivity estimates, galvanic distortion correction, especially static shift correction, is essential.

Scale distortion correction of a digital micromirror device using diffraction caustics

2020 ◽  
Vol 134 ◽  
pp. 106122
Author(s):  
Jadze Princeton C. Narag ◽  
Niña Angelica F. Zambale ◽  
Nathaniel Hermosa
Keyword(s):  
Distortion Correction ◽  
Digital Micromirror Device

Fringe-Distortion-Correction for Polarized Low-Coherence Interferometry With Phosphor-Based LED

2019 ◽  
Vol 37 (14) ◽  
pp. 3557-3562
Author(s):  
Rundong Wang ◽  
Shuang Wang ◽  
Junfeng Jiang ◽  
Kun Liu ◽  
Xue Wang ◽  
...  
Keyword(s):  
Distortion Correction ◽  
Low Coherence ◽  
Low Coherence Interferometry
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