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1
Cavanagh, Patrick, and Yvan G. Leclerc. "Shape from shadows." Journal of Experimental Psychology: Human Perception and Performance 15, no. 1 (1989): 3–27. http://dx.doi.org/10.1037/0096-1523.15.1.3.
2
Hatzitheodorou, Michael. "Shape from Shadows." Journal of Complexity 14, no. 1 (March 1998): 63–84. http://dx.doi.org/10.1006/jcom.1997.0448.
3
Chappelow, J. E. "Simple impact crater shape determination from shadows." Meteoritics & Planetary Science 48, no. 10 (September 24, 2013): 1863–72. http://dx.doi.org/10.1111/maps.12201.
4
Cavanagh, Patrick, and Yvan G. Leclerc. ""Shape from shadows": Correction to Cavanagh and Leclerc (1989)." Journal of Experimental Psychology: Human Perception and Performance 16, no. 4 (1990): 910. http://dx.doi.org/10.1037/0096-1523.16.4.910.
5
Yamashita, Yukihiro, Fumihiko Sakaue, and Jun Sato. "Fast 3D Shape Recovery from Shadows Projected on Arbitrary Curved Surfaces." International Journal of Virtual Reality 9, no. 1 (January 1, 2010): 1–6. http://dx.doi.org/10.20870/ijvr.2010.9.1.2754.
Анотація:
The shadow based 3D surface reconstruction methods usually assume that shadows are projected on planar surfaces. However, shadows are often projected on curved surfaces in the real scene. Recently, the shadow graph has been proposed for representing shadow information efficiently, and for recovering 3D shapes from shadows projected on curved surfaces. Unfortunately, the method requires a large computational cost and is weak to the image intensity noises. In this paper, we introduce 1D shadow graphs which can represent shadow information quite efficiently, and can be used for recovering 3D shapes with much smaller computational costs than before. We also extend our method, so that we can recover 3D shape quite accurately by using shading information as well as shadow information. The proposed method is tested by using the real and synthetic images.
6
Norman, J. Farley, Thomas E. Dawson, and Shane R. Raines. "The Perception and Recognition of Natural Object Shape from Deforming and Static Shadows." Perception 29, no. 2 (February 2000): 135–48. http://dx.doi.org/10.1068/p2994.
Анотація:
In this study of the informativeness of shadows for the perception of object shape, observers viewed shadows cast by a set of natural solid objects and were required to discriminate between them. In some conditions the objects underwent rotation in depth while in other conditions they remained stationary, thus producing both deforming and static shadows. The orientation of the light source casting the shadows was also varied, leading to further alterations in the shape of the shadows. When deformations in the shadow boundary were present, the observers were able to reliably recognize and discriminate between the objects, invariant over the shadow distortions produced by movements of the light source. The recognition performance for the static shadows depended critically upon the content of the specific views that were shown. These results support the idea that there are invariant features of shadow boundaries that permit the recognition of shape (cf Koenderink, 1984 Perception13 321–330).
7
Castiello, Umberto, Dean Lusher, Carol Burton, and Peter Disler. "Shadows in the Brain." Journal of Cognitive Neuroscience 15, no. 6 (August 1, 2003): 862–72. http://dx.doi.org/10.1162/089892903322370780.
Анотація:
The aims of the present study were to investigate whether the processing of an object shadow occurs implicitly, that is without conscious awareness, and where physically within the human brain shadows are processed. Here we present neurological evidence, obtained from studies of brain-injured patients with visual neglect, that shadows are implicitly processed and that this processing may take place within the temporal lobe. Neglect patients with lesions that do not involve the right temporal lobe were still able to process shadows to optimize object shape perception. In contrast, shadow processing was not found to be as efficient in neglect patients with lesions that involve the right temporal lobe.
8
Norman, J. F., Y. l. Lee, F. Phillips, H. F. Norman, L. R. Jennings, and T. R. McBride. "The perception of 3-D shape from shadows cast onto curved surfaces." Journal of Vision 9, no. 8 (March 24, 2010): 60. http://dx.doi.org/10.1167/9.8.60.
9
Norman, J. Farley, Young-lim Lee, Flip Phillips, Hideko F. Norman, L. RaShae Jennings, and T. Ryan McBride. "The perception of 3-D shape from shadows cast onto curved surfaces." Acta Psychologica 131, no. 1 (May 2009): 1–11. http://dx.doi.org/10.1016/j.actpsy.2009.01.007.
10
Koizumi, Tomomi, Hiroyuki Ito, Shoji Sunaga, and Masaki Ogawa. "Directional Bias in the Perception of Cast Shadows." i-Perception 8, no. 1 (January 2017): 204166951668226. http://dx.doi.org/10.1177/2041669516682267.
Анотація:
Previous studies have demonstrated that the perception of shading is based upon assumptions about lighting direction, for example, light from above. However, it is not clear whether these assumptions are used in the perception of cast shadows. Moreover, it is unclear whether a perceptual interaction exists between shading and cast shadows because until now they have been studied separately. In this study, we investigated through three experiments whether the light-from-above (or another direction) assumption is used in interpreting ambiguous cast shadows, and whether shading information influences the interpretation of cast shadows. Our results indicate the existence of the light-from-above assumption in interpreting cast shadows. Consistent shading information enhanced the interpretation, and judgments of lighting direction were also based on both cast shadow and shading information. However, the perceptual determination of shape from shading was relatively independent of the cast shadow interpretation or the lighting direction judgments of the scene.
11
Maeda, Shinya, Yasuyuki Tomiyama, Hyoungseop Kim, Noriaki Miyake, Yoshinori Itai, Joo Kooi Tan, Seiji Ishikawa, and Akiyoshi Yamamoto. "Detection of Lung Nodules in Thoracic MDCT Images Based on Temporal Changes from Previous and Current Images." Journal of Advanced Computational Intelligence and Intelligent Informatics 15, no. 6 (August 20, 2011): 707–13. http://dx.doi.org/10.20965/jaciii.2011.p0707.
Анотація:
Temporal subtraction enhances temporal change by subtracting images captured at different times. Medical images captured currently (current images) and in previous examination (previous images) are subtracted to enhance new lesions and temporal change in existing lesion shadows. Temporal subtraction using chest MultiDetector-Row Computed Tomography (MDCT) images and currently being developed is to be applied to nodule detection in pulmonary regions. Nodule detection using conventional temporal subtraction, however, yields many false-positive results for those 20 mm or less in diameter, requiring improvement. We discuss improvements in nodule detection accuracy using temporal subtraction, first extracting rough nodules from temporal subtraction images as candidate shadows. Features are then acquired from current, previous, and temporal subtraction images. We use intensity features in previous images and shape features in the current images and in features used in conventional methods. Using acquired features, we build a neural network classifier, then extract final pulmonary candidates in unknown shadows.
12
HIRATSUKA, TOMOKAZU, KEIICHI HORIO, and TAKESHI YAMAKAWA. "SURFACE ROUGHNESS MEASUREMENT USING SHADOWS PRODUCED BY CIRCULATING LIGHT SOURCES." New Mathematics and Natural Computation 05, no. 01 (March 2009): 335–52. http://dx.doi.org/10.1142/s1793005709001349.
Анотація:
We propose a new measurement method for a degree of roughness of a given object surface. This method is not to measure the degree of roughness of the object surface directly, but to estimate the roughness from surface images. Named as circulating light sources (CLS), its multiple light sources aligned in a circle illuminate sequentially, and produce images including shadow of the object surface. As the shadows on the images reflect a shape of the object surface, the shapes of the surface, concavo-convex shape, can be estimated by these shadows. In this paper, features of surface roughness are extracted by a Wavelet Multiresolution Analysis (MRA) from the shadow images produced by the CLS, and are classified by a Self-Organizing Map (SOM). A roughness of an unknown surface can be estimated by the SOM after learning.
13
Fu, Haoyang, Tingting Zhou, and Chenglin Sun. "Object-Based Shadow Index via Illumination Intensity from High Resolution Satellite Images over Urban Areas." Sensors 20, no. 4 (February 17, 2020): 1077. http://dx.doi.org/10.3390/s20041077.
Анотація:
For multi-spectral remote sensing imagery, accurate shadow extraction is of great significance for overcoming the information loss caused by high buildings and the solar incidence angle in urban remote sensing. However, diverse solar illumination conditions, similarities between shadows, and other dark land features bring uncertainties and deviations to shadow extraction processes and results. In this paper, we classify shadows as either strong or weak based on the ratio between ambient light intensity and direct light intensity, and use the fractal net evolution approach (FNEA), which is a multi-scale segmentation method based on spectral and shape heterogeneity, to reduce the interference of salt and pepper noise and relieve the error of misdiagnosing land covers with high reflectivity in shaded regions as unshaded ones. Subsequently, an object-based shadow index (OSI) is presented according to the illumination intensities of different reflectance features, as well as using the normalized difference water index (NDWI) and near infrared (NIR) band to highlight shadows and eliminate water body interference. The data from three high-spatial-resolution satellites—WorldView-2 (WV-2), WorldView-3 (WV-3), and GaoFen-2 (GF-2)—were used to test the methods and verify the robustness of the OSI. The results show that the OSI index performed well regarding both strong and weak shadows with the user accuracy and the producer accuracy both above 90%, while the four other existing indexes that were tested were not effective at diverse solar illumination conditions. In addition, all the disturbances from water body were excluded well when using the OSI, except for the GF-2 data in weak shadows.
14
Yang, Lingyun, and Zilong Li. "Shadow of a dressed black hole and determination of spin and viewing angle." International Journal of Modern Physics D 25, no. 02 (February 2016): 1650026. http://dx.doi.org/10.1142/s0218271816500267.
Анотація:
Shadows of black holes surrounded by an optically thin emitting medium have been extensively discussed in the literature. The Hioki–Maeda algorithm is a simple recipe to characterize the shape of these shadows and determine the parameters of the system. Here, we extend their idea to the case of a dressed black hole, namely a black hole surrounded by a geometrically thin and optically thick accretion disk. While the boundary of the shadow of black holes surrounded by an optically thin emitting medium corresponds to the apparent photon capture sphere, that of dressed black holes corresponds to the apparent image of the innermost stable circular orbit (ISCO). Even in this case, we can characterize the shape of the shadow and infer the black hole spin and viewing angle. The shape and the size of the shadow of a dressed black hole are strongly affected by the black hole spin and inclination angle. Despite that, it seems that we cannot extract any additional information from it. Here, we study the possibility of testing the Kerr metric. Even with the full knowledge of the boundary of the shadow, those of Kerr and non-Kerr black holes are very similar and it is eventually very difficult to distinguish the two cases.
15
Warshawsky, H. "Enamel Crystal Shape: History of an Idea." Advances in Dental Research 1, no. 2 (December 1987): 322–29. http://dx.doi.org/10.1177/08959374870010022401.
Анотація:
The purpose of this paper is to review evidence which casts doubt on the interpretation universally applied to hexagonal images seen in sectioned enamel. The evidence is based on two possible models to explain the hexagonal profiles seen in mammalian enamel with transmission electron microscopy. The "hexagonal ribbon" model proposes that hexagonal profiles are true cross-sections of elongated hexagonal ribbons. The "rectangular ribbon" model proposes that hexagonal profiles are caused by three-dimensional segments that are parallelepipeds contained in the Epon section. Since shadow projections of such rectangular segments give angles that are inconsistent with the hexagonal unit cell, a model based on ribbons with rhomboidal cut ends and angles of 60 and 120° is proposed. The "rhomboidal ribbon" model projects shadows with angles that are predicted by the unit cell. It is suggested that segments of such crystallites in section project as opaque hexagons on the imaging plane in routine transmission electron microscopy. Morphological observations on crystallites in sections - together with predictions from the hexagonal, rectangular, and rhomboidal ribbon models - indicate that crystallites in rat incisor enamel are flat ribbons with rhomboidal cross-sectional shape. Hexagonal images in electron micrographs of thin-sectioned enamel can result from rhomboidal-ended, parallelepiped-shaped segments of these crystallites projected and viewed as two-dimensional shadows.
16
Afrin, Misba, Rahul Kumar, and Sushant G. Ghosh. "Parameter estimation of hairy Kerr black holes from its shadow and constraints from M87*." Monthly Notices of the Royal Astronomical Society 504, no. 4 (May 4, 2021): 5927–40. http://dx.doi.org/10.1093/mnras/stab1260.
Анотація:
ABSTRACT The recently obtained hairy Kerr black holes, due to additional sources or surrounding fluid, like dark matter, with conserved energy-momentum tensor, have a deviation α and primary hair l0, apart from rotation parameter a and mass M. In the wake of the Event Horizon Telescope (EHT) observations of the supermassive black hole M87*, a recent surge in interest in black hole shadows suggests comparing the black holes in general relativity and modified theories of gravity to assess these models’ differences. Motivated by this, we take on an extensive study of the rotating hairy Kerr black holes, which encompasses, in particular cases, the Kerr black hole (α = 0). We investigate ergosphere and shadows of the black holes to infer that their size and shape are affected due to the l0 and are found to harbour a richer chaotic structure. In particular, the hairy Kerr black holes possess smaller size but more distorted shadows when compared with Kerr black holes. We also estimate the parameters l0 and a associated with hairy Kerr black holes using the shadow observables. The inferred circularity deviation ΔC ≤ 0.1 for the M87* black hole is satisfied, whereas shadow angular diameter θd = 42 ± 3μas, within 1σ region, for a given choice of α, places bounds on the parameters a and l0. Interestingly, the shadow axial ratio obeying 1 < Dx ≲ 4/3 is in agreement with the EHT results and thus eventuates in the hairy Kerr black holes being suitable candidates for astrophysical black holes.
17
Hess, M., K. Wohlfarth, A. Grumpe, C. Wöhler, O. Ruesch, and B. Wu. "ATMOSPHERICALLY COMPENSATED SHAPE FROM SHADING ON THE MARTIAN SURFACE: TOWARDS THE PERFECT DIGITAL TERRAIN MODEL OF MARS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W13 (June 5, 2019): 1405–11. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w13-1405-2019.
Анотація:
<p><strong>Abstract.</strong> We have expanded our existing Shape and Albedo from Shading framework which has primarily been used to generate Digital Terrain Models (DTMs) of the Lunar Surface. The extension consists of an atmospheric model such that the approach can be applied to Mars which is covered by a thin atmosphere. The atmospheric model includes attenuation by the atmosphere, diffuse illumination of the surface and scattering from the atmosphere into the direction of the sensor with physically motivated parameters. To estimate the newly introduced atmospheric parameters without additional CRISM measurements, the radiance image and an initializing surface are used. The initial surface is derived from stereo images and serves two purposes. On the one hand, it is the height constraint of the SfS algorithm and on the other hand, it is used for estimating the atmospheric parameters. Relying on this estimation, the aforementioned Shape and Albedo from Shading method is carried out. The results show a considerable improvement compared to DTMs derived with stereo algorithms. The omnipresent stereo artifacts such as pixel locking and mismatches are smoothed out and small details are reconstructed convincingly. The procedure is then compared to the reconstruction without atmospheric compensation. Images in which shadows are present benefit from this method because shadows can now be described by the diffuse illumination of the surface. The reconstruction results indicate the viability of the approach since it can produce convincing DTMs compared to HiRISE ground truth.</p>
18
Ridene, Safa, Reda Yaagoubi, Imane Sebari, and Audrey Alajouanine. "Shadow detection and correction using a combined 3D GIS and image processing approach." Revue Internationale de Géomatique 29, no. 3-4 (July 2019): 241–53. http://dx.doi.org/10.3166/rig.2019.00091.
Анотація:
While shadow can give useful information about size and shape of objects, it can pose problems in feature detection and object detection, thereby, it represents one of the major perturbator phenomenons frequently occurring on images and unfortunately, it is inevitable. “Shadows may lead to the failure of image analysis processes and also cause a poor quality of information which in turn leads to problems in implementation of algorithms.” (Mahajan and Bajpayee, 2015). It also affects multiple image analysis applications, whereby shadow cast by buildings deteriorate the spectral values of the surfaces. Therefore, its presence causes a deterioration in the visual image's quality and limits the information that the former could give. Ignoring the existence of shadows in images may cause serious problems in various visual processing applications such as false objects detection. In this context, many researches have been conducted through years. However, it is still a challenge for analysts all over the world to find a fully automated and efficient method for shadow removal from images.
19
Johnston, Alan, Harold Hill, and Nicole Carman. "Recognising Faces: Effects of Lighting Direction, Inversion, and Brightness Reversal." Perception 21, no. 3 (June 1992): 365–75. http://dx.doi.org/10.1068/p210365.
Анотація:
When information about three-dimensional shape obtained from shading and shadows is ambiguous, the visual system favours an interpretation of surface geometry which is consistent with illumination from above. If pictures of top-lit faces are rotated the resulting stimulus is both figurally inverted and illuminated from below. In this study the question of whether the effects of figural inversion and lighting orientation on face recognition are independent or interactive is addressed. Although there was a clear inversion effect for faces illuminated from the front and above, the inversion effect was found to be reduced or eliminated for faces illuminated from below. A strong inversion effect for photographic negatives was also found but in this case the effect was not dependent on the direction of illumination. These findings are interpreted as evidence to suggest that lighting faces from below disrupts the formation of surface-based representations of facial shape.
20
Domokos, Gábor, Douglas J. Jerolmack, Ferenc Kun, and János Török. "Plato’s cube and the natural geometry of fragmentation." Proceedings of the National Academy of Sciences 117, no. 31 (July 17, 2020): 18178–85. http://dx.doi.org/10.1073/pnas.2001037117.
Анотація:
Plato envisioned Earth’s building blocks as cubes, a shape rarely found in nature. The solar system is littered, however, with distorted polyhedra—shards of rock and ice produced by ubiquitous fragmentation. We apply the theory of convex mosaics to show that the average geometry of natural two-dimensional (2D) fragments, from mud cracks to Earth’s tectonic plates, has two attractors: “Platonic” quadrangles and “Voronoi” hexagons. In three dimensions (3D), the Platonic attractor is dominant: Remarkably, the average shape of natural rock fragments is cuboid. When viewed through the lens of convex mosaics, natural fragments are indeed geometric shadows of Plato’s forms. Simulations show that generic binary breakup drives all mosaics toward the Platonic attractor, explaining the ubiquity of cuboid averages. Deviations from binary fracture produce more exotic patterns that are genetically linked to the formative stress field. We compute the universal pattern generator establishing this link, for 2D and 3D fragmentation.
21
Garcia-Fernandez, J., L. Medeiros, and J. Pernão. "REPRESENTATION OF SYNTHETIC SHADOWS ON 3D DIGITAL MODELS FOR THE VOLUMETRIC INTERPRETATION ON CONCAVE-CONVEX ARCHAEOLOGICAL ARTIFACTS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W9 (January 31, 2019): 355–59. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w9-355-2019.
Анотація:
<p><strong>Abstract.</strong> The representation of archaeological artefacts aims for the graphic description of relevant information from the object, to allow for the proper interpretation of evidences from the past. Concavities and convexities are elements often difficult to represent through classical (analogical) representation techniques, especially when these geometrical characteristics are neither continue nor parameterizable. Digital techniques have advanced on the accurate reconstruction of 3D shapes, while attaching real colour to the geometry. However, the perception of concave/convex shapes from photorealistic true-orthoimages continues to be limited, especially when rich and homogeneous textures camouflage slight slope changes or volumetric deformations. In this paper we first critically review the current practice on the representation of solid-of-revolution artefacts with concave-convex predominance, and alternative photorealistic representations aiming at a better understanding of volume and colour. Given the limitation targeted, we then propose a workflow for the creation of true-orthometric maps enhanced by customized shadows. The work-flow integrates considerations on: (i) The orientation of archaeological artefact; (ii) the creation of accurate orthometric images based on Digital photogrammetry techniques; and (iii) the application of synthetic attached and cast shadows according the shape (information) to be represented. The workflow is demonstrated with a sample of plates retrieved from the Rua-das-Madres archaeological site, in Portugal.</p>
22
Kay, E., M. Tisdall, and Malcolm Hill. "Policy Change under Devolution: The Prism of Children's Policy." Social Policy and Society 10, no. 1 (December 8, 2010): 29–40. http://dx.doi.org/10.1017/s1474746410000369.
Анотація:
Children's policy has emerged from the shadows of family and education policy over the last decade throughout the UK. The decade has also seen political and policy transformation, with the change of government from Conservatives to New Labour in 1997 and the latter's delivery on its promise of devolved administrations. Devolution has accompanied claims and attempts to move from ‘government to governance’, to recognise and support partnerships and encourage greater civic engagement.Scottish children's policy is a prism to review key questions of devolution and its impact on policy change. The article traces and considers policy trends, to conclude that distinctive government structures have interacted with other influences to shape change, allowing more and ‘new’ room for community interests, political parties and distinctive policies.
23
Zhang, Xiuming, Pratul P. Srinivasan, Boyang Deng, Paul Debevec, William T. Freeman, and Jonathan T. Barron. "NeRFactor." ACM Transactions on Graphics 40, no. 6 (December 2021): 1–18. http://dx.doi.org/10.1145/3478513.3480496.
Анотація:
We address the problem of recovering the shape and spatially-varying reflectance of an object from multi-view images (and their camera poses) of an object illuminated by one unknown lighting condition. This enables the rendering of novel views of the object under arbitrary environment lighting and editing of the object's material properties. The key to our approach, which we call Neural Radiance Factorization (NeRFactor), is to distill the volumetric geometry of a Neural Radiance Field (NeRF) [Mildenhall et al. 2020] representation of the object into a surface representation and then jointly refine the geometry while solving for the spatially-varying reflectance and environment lighting. Specifically, NeRFactor recovers 3D neural fields of surface normals, light visibility, albedo, and Bidirectional Reflectance Distribution Functions (BRDFs) without any supervision, using only a re-rendering loss, simple smoothness priors, and a data-driven BRDF prior learned from real-world BRDF measurements. By explicitly modeling light visibility, NeRFactor is able to separate shadows from albedo and synthesize realistic soft or hard shadows under arbitrary lighting conditions. NeRFactor is able to recover convincing 3D models for free-viewpoint relighting in this challenging and underconstrained capture setup for both synthetic and real scenes. Qualitative and quantitative experiments show that NeRFactor outperforms classic and deep learning-based state of the art across various tasks. Our videos, code, and data are available at people.csail.mit.edu/xiuming/projects/nerfactor/.
24
Lundgreen-Nielsen, Flemming. "Naar Skyggen er ligest..." Grundtvig-Studier 52, no. 1 (January 1, 2001): 58–69. http://dx.doi.org/10.7146/grs.v52i1.16396.
Анотація:
»When the Shadow comes nearest..« By Flemming Lundgreen-NielsenThis small contribution deals with two intricate lines from stanza 5 of Grundtvig’s 1824 poem .The Land of the Living.. They are usually taken to mean that when likeness in the shape of shadows comes nearest the real thing, the little ones observing them weep, because in human poetry and arts which strive to reflect eternity similarity is not and can never be identity. Chr. Thodberg has repeatedly since 1971 suggested a different understanding of the lines to the effect that »ligest« (i.e. .most similar to.) may be interpreted as »most vertical«, referring to the shrinkage or entire disappearance of shadows at noon, when the sun reaches zenith. Thodberg departs from an off-hand commentary by Grundtvig about this natural fact in a sermon delivered on 27 March 1823. The author tries to demonstrate that Grundtvig's varying usage of theword shadow (»Skygge«) both before and after 1824 makes it impossible to arrive at an unambiguous determination regarding the word in the said lines. Furthermore, the superlative degree »ligest« meaning »most vertical« neither seems to have been recorded in the language of Grundtvig and his contemporaries nor in older periods.Contrarily, »ligest« meaning »most similar to« can be found in ancient Danish proverbs which Grundtvig studied extensively from 1816 and until he edited and published a collection of them in 1845, and it can also be located in contemporary literature. Returning from there to the meaning of shadow, the author by means of quotes from Grundtvig’s brief but precise historical evaluations of Plato and his philosophy (in 1812 and 1833) is inclined to support the traditional interpretation that the shadows making little ones weep originate in the famous cave metaphor in the fifth book of Plato’s dialogue The Republic. Finally, two other details deriving from Grundtvig’s studies of Danish proverbs in the Peder Syv edition (1688) are mentioned to throw light on a couple of nebulous expressions in two other lyrical poems by him.
25
Polewski, P., W. Yao, M. Heurich, P. Krzystek, and U. Stilla. "DETECTION OF SINGLE STANDING DEAD TREES FROM AERIAL COLOR INFRARED IMAGERY BY SEGMENTATION WITH SHAPE AND INTENSITY PRIORS." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences II-3/W4 (March 11, 2015): 181–88. http://dx.doi.org/10.5194/isprsannals-ii-3-w4-181-2015.
Анотація:
Standing dead trees, known as snags, are an essential factor in maintaining biodiversity in forest ecosystems. Combined with their role as carbon sinks, this makes for a compelling reason to study their spatial distribution. This paper presents an integrated method to detect and delineate individual dead tree crowns from color infrared aerial imagery. Our approach consists of two steps which incorporate statistical information about prior distributions of both the image intensities and the shapes of the target objects. In the first step, we perform a Gaussian Mixture Model clustering in the pixel color space with priors on the cluster means, obtaining up to 3 components corresponding to dead trees, living trees, and shadows. We then refine the dead tree regions using a level set segmentation method enriched with a generative model of the dead trees’ shape distribution as well as a discriminative model of their pixel intensity distribution. The iterative application of the statistical shape template yields the set of delineated dead crowns. The prior information enforces the consistency of the template’s shape variation with the shape manifold defined by manually labeled training examples, which makes it possible to separate crowns located in close proximity and prevents the formation of large crown clusters. Also, the statistical information built into the segmentation gives rise to an implicit detection scheme, because the shape template evolves towards an empty contour if not enough evidence for the object is present in the image. We test our method on 3 sample plots from the Bavarian Forest National Park with reference data obtained by manually marking individual dead tree polygons in the images. Our results are scenario-dependent and range from a correctness/completeness of 0.71/0.81 up to 0.77/1, with an average center-of-gravity displacement of 3-5 pixels between the detected and reference polygons.
26
Kurniawan, Aditya, and Kholilatul Wardani. "Kinect Structural Noise Elimination Technique For ITIS Mobile Robot Data Collector." International Journal of Engineering & Technology 7, no. 4.27 (November 30, 2018): 1. http://dx.doi.org/10.14419/ijet.v7i4.27.22425.
Анотація:
A contemporary study on the Kinect sensor as a visual sensor device for robots shows that the sensor has some fundamental flaws. One of them are shadows on the object edge that will affect the process of recognition of shape (shape recognition) spatially. If the Kinect sensor is used in the robot vision navigation system, the sensor may lead to errors in the robot's decision on the shape of the object sensed by the sensor. The previous research reports a positive influence on the variation of smoothing process by using neighborhood filtering. This research will use multiple neighborhood localized filtering (MNLF) method to eliminate structural noise generated by kinect sensor IR camera. The robot model that will be used for testing is 6WD Wild Thumper Mobile Robot Chassis from Dagu Robotics. The calculation of SSI (Structural Similarity Index) calculation based on ROI between image index 0 (original image) with index 6 (image result after multiple filtering process) results SSI index with value 0.999999930515914. This indicates that multiple filtering processes do not affect the quality of images produced by Kinect sensors. The number of 0.99 can be rounded to 1 so that the conclusion based on ROI image assessment shows no differences on image quality after process.
27
Bial, J., and C. A. Trepmann. "The microstructural record of porphyroclasts and matrix of partly serpentinized peridotite mylonites – from brittle and crystal-plastic deformation to dissolution–precipitation creep." Solid Earth 4, no. 2 (October 11, 2013): 315–30. http://dx.doi.org/10.5194/se-4-315-2013.
Анотація:
Abstract. We present microfabrics in high-pressure, metamorphic, partly serpentinized peridotite mylonites from the Voltri Massif, in which porphyroclasts and matrix record independent deformation events. The microfabrics are analysed using polarization microscopy and electron microscopy (SEM/EBSD, EMP). The mylonites contain diopside and olivine porphyroclasts originating from the mantle protolith embedded in a fine-grained matrix consisting mainly of antigorite and minor olivine and pyroxene. The porphyroclasts record brittle and crystal-plastic deformation of the peridotite at upper-mantle conditions and differential stresses of a few hundred MPa. After the peridotites became serpentinized, deformation occurred mainly by dissolution–precipitation creep resulting in a pronounced foliation of the antigorite matrix, crenulation cleavages and newly precipitated olivine and pyroxene from the pore fluid at sites of dilation, i.e. in strain shadows next to porphyroclasts and folded fine-grained antigorite layers. Antigorite reveals a pronounced associated shape preferred orientation (SPO) and crystallographic preferred orientation (CPO) with the basal (001) cleavage plane oriented in the foliation plane. In monomineralic antigorite aggregates at sites of stress concentration around porphyroclasts, a characteristically reduced grain size and deflecting CPO as well as sutured grain boundaries indicate also some contribution of crystal-plastic deformation and grain-boundary migration of antigorite. In contrast, the absence of any intragranular deformation features in newly precipitated olivine in strain shadows reveals that stresses were not sufficiently high to allow for significant dislocation creep of olivine at conditions at which antigorite is stable. The porphyroclast microstructures are not associated with the microstructures of the mylonitic matrix, but are inherited from an independent earlier deformation. The porphyroclasts record a high-stress deformation of the peridotite with dislocation creep of olivine in the upper mantle probably related to rifting processes, whereas the serpentinite matrix records dominantly dissolution–precipitation creep and low stresses during subduction and exhumation.
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Bergström, S. S., K.-A. Gustafsson, and T. Jakobsson. "A Colour Constancy Phenomenon Related to Perceived 3-D Shape." Perception 25, no. 1_suppl (August 1996): 11. http://dx.doi.org/10.1068/v96p0105.
Анотація:
Flat, rectangular displays consisting of 2, 3, 4, or 6 vertical grey stripes, alternately light and dark gray (NCS 3500 and NCS 6000, respectively) were presented one at a time illuminated by two identical projectors. One projector illuminated the upper half of the display through a yellowish colour filter (Strand Golden Amber), and the other one illuminated the lower half through a bluish colour filter (Kodak Wratten 80 A). The display appeared ambiguous, periodically and spontaneously shifting between two distinct 3-D shape percepts, A and B. Display A appeared vertically folded along the reflectance edges (‘shape from shading’, where the dark fields appeared to be attached shadows). The colours were quite saturated yellow and blue surface colours. There was no colour constancy; Display B appeared horizontally folded along the illumination edge like a roof (‘shape from shading’, where one of the illuminations appeared to be an attached shadow). The display now appeared very desaturated, even achromatic, but in a ‘warm’ illumination. The colour constancy was almost complete. The phenomenon is demonstrated with a slide, and some psychophysical data on the colour desaturation and on the frequency of shifts between the two percepts are reported as well as some observations on combinations of illuminant colours other than yellow and blue. The reported colour constancy phenomenon is discussed in relation to an earlier presented model for the perception of illumination, colour, and depth [S S Bergström, 1994, in Lightness, Brightness, and Transparency Ed. A Gilchrist (Hillsdale, NJ: Lawrence Erlbaum Associates)].
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Muro-Arena, G. A., M. Benisty, C. Ginski, C. Dominik, S. Facchini, M. Villenave, R. van Boekel, et al. "Shadowing and multiple rings in the protoplanetary disk of HD 139614." Astronomy & Astrophysics 635 (March 2020): A121. http://dx.doi.org/10.1051/0004-6361/201936509.
Анотація:
Context. Shadows in scattered light images of protoplanetary disks are a common feature and support the presence of warps or misalignments between disk regions. These warps are possibly caused by an inclined (sub-)stellar companion embedded in the disk. Aims. We aim to study the morphology of the protoplanetary disk around the Herbig Ae star HD 139614 based on the first scattered light observations of this disk, which we model with the radiative transfer code MCMax3D. Methods. We obtained J- and H-band observations that show strong azimuthal asymmetries in polarized scattered light with VLT/SPHERE. In the outer disk, beyond ~30 au, a broad shadow spans a range of ~240 deg in position angle, in the east. A bright ring at ~16 au also shows an azimuthally asymmetric brightness, with the faintest side roughly coincidental with the brightest region of the outer disk. Additionally, two arcs are detected at ~34 and ~50 au. We created a simple four-zone approximation to a warped disk model of HD 139614 in order to qualitatively reproduce these features. The location and misalignment of the disk components were constrained from the shape and location of the shadows they cast. Results. We find that the shadow on the outer disk covers a range of position angles too wide to be explained by a single inner misaligned component. Our model requires a minimum of two separate misaligned zones – or a continuously warped region – to cast this broad shadow on the outer disk. A small misalignment of ~4° between adjacent components can reproduce most of the observed shadow features. Conclusions. Multiple misaligned disk zones, potentially mimicking a warp, can explain the observed broad shadows in the HD 139614 disk. A planetary mass companion in the disk, located on an inclined orbit, could be responsible for such a feature and for the dust-depleted gap responsible for a dip in the SED.
30
Chen, Li, Qing Zhu, Xiao Xie, Han Hu, and Haowei Zeng. "Road Extraction from VHR Remote-Sensing Imagery via Object Segmentation Constrained by Gabor Features." ISPRS International Journal of Geo-Information 7, no. 9 (September 2, 2018): 362. http://dx.doi.org/10.3390/ijgi7090362.
Анотація:
Automatic road extraction from remote-sensing imagery plays an important role in many applications. However, accurate and efficient extraction from very high-resolution (VHR) images remains difficult because of, for example, increased data size and superfluous details, the spatial and spectral diversity of road targets, disturbances (e.g., vehicles, shadows of trees, and buildings), the necessity of finding weak road edges while avoiding noise, and the fast-acquisition requirement of road information for crisis response. To solve these difficulties, a two-stage method combining edge information and region characteristics is presented. In the first stage, convolutions are executed by applying Gabor wavelets in the best scale to detect Gabor features with location and orientation information. The features are then merged into one response map for connection analysis. In the second stage, highly complete, connected Gabor features are used as edge constraints to facilitate stable object segmentation and limit region growing. Finally, segmented objects are evaluated by some fundamental shape features to eliminate nonroad objects. The results indicate the validity and superiority of the proposed method to efficiently extract accurate road targets from VHR remote-sensing images.
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Adams, Wendy J., Erich W. Graf, and Matt Anderson. "Disruptive coloration and binocular disparity: breaking camouflage." Proceedings of the Royal Society B: Biological Sciences 286, no. 1896 (February 13, 2019): 20182045. http://dx.doi.org/10.1098/rspb.2018.2045.
Анотація:
Many species employ camouflage to disguise their true shape and avoid detection or recognition. Disruptive coloration is a form of camouflage in which high-contrast patterns obscure internal features or break up an animal's outline. In particular, edge enhancement creates illusory, or ‘fake’ depth edges within the animal's body. Disruptive coloration often co-occurs with background matching, and together, these strategies make it difficult for an observer to visually segment an animal from its background. However, stereoscopic vision could provide a critical advantage in the arms race between perception and camouflage: the depth information provided by binocular disparities reveals the true three-dimensional layout of a scene, and might, therefore, help an observer to overcome the effects of disruptive coloration. Human observers located snake targets embedded in leafy backgrounds. We analysed performance (response time) as a function of edge enhancement, illumination conditions and the availability of binocular depth cues. We confirm that edge enhancement contributes to effective camouflage: observers were slower to find snakes whose patterning contains ‘fake’ depth edges. Importantly, however, this effect disappeared when binocular depth cues were available. Illumination also affected detection: under directional illumination, where both the leaves and snake produced strong cast shadows, snake targets were localized more quickly than in scenes rendered under ambient illumination. In summary, we show that illusory depth edges, created via disruptive coloration, help to conceal targets from human observers. However, cast shadows and binocular depth information improve detection by providing information about the true three-dimensional structure of a scene. Importantly, the strong interaction between disparity and edge enhancement suggests that stereoscopic vision has a critical role in breaking camouflage, enabling the observer to overcome the disruptive effects of edge enhancement.
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Verma, Niva Kiran, and David W. Lamb. "The use of shadows in high spatial resolution, remotely sensed, imagery to estimate the height of individual Eucalyptus trees on undulating land." Rangeland Journal 37, no. 5 (2015): 467. http://dx.doi.org/10.1071/rj15021.
Анотація:
The shadows cast by 180 individual Eucalyptus trees, of varying canopy condition, on undulating land in south-eastern Australia were used to infer their heights from 50-cm spatial resolution, multispectral aerial imagery (blue = 0.4–0.5 μm; green = 0.5–0.6 μm; red = 0.6–0.7 μm; near infrared = 0.7–1 μm). A geometrical shadow model was developed incorporating the local slope and aspect of the ground from a digital elevation model at each tree location. A method of deriving ‘local tree time’ to infer the solar elevation angle, in situations where the image acquisition time is not available, was also developed. Based on a measurement of the shadow length from the geometric centre of the tree crowns, and ignoring the role of the crown periphery in distorting the shadow shape, the tree heights were estimated with a root mean square error of ±5.6 m (~±27%) with some overestimated by as much as 50%. A geometric correction for shadow distortion assuming spherical crown geometry provided an improved estimate with a root mean square error of ±4.8 m (~±23%).
33
Michalak, Hubert, and Krzysztof Okarma. "Improvement of Image Binarization Methods Using Image Preprocessing with Local Entropy Filtering for Alphanumerical Character Recognition Purposes." Entropy 21, no. 6 (June 4, 2019): 562. http://dx.doi.org/10.3390/e21060562.
Анотація:
Automatic text recognition from the natural images acquired in uncontrolled lighting conditions is a challenging task due to the presence of shadows hindering the shape analysis and classification of individual characters. Since the optical character recognition methods require prior image binarization, the application of classical global thresholding methods in such case makes it impossible to preserve the visibility of all characters. Nevertheless, the use of adaptive binarization does not always lead to satisfactory results for heavily unevenly illuminated document images. In this paper, the image preprocessing methodology with the use of local image entropy filtering is proposed, allowing for the improvement of various commonly used image thresholding methods, which can be useful also for text recognition purposes. The proposed approach was verified using a dataset of 140 differently illuminated document images subjected to further text recognition. Experimental results, expressed as Levenshtein distances and F-Measure values for obtained text strings, are promising and confirm the usefulness of the proposed approach.
34
Chen, J., J. L. Hou, and M. Deng. "AN APPROACH TO ALLEVIATE THE FALSE ALARM IN BUILDING CHANGE DETECTION FROM URBAN VHR IMAGE." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (June 21, 2016): 459–65. http://dx.doi.org/10.5194/isprsarchives-xli-b7-459-2016.
Анотація:
Building change detection from very-high-resolution (VHR) urban remote sensing image frequently encounter the challenge of serious false alarm caused by different illumination or viewing angles in bi-temporal images. An approach to alleviate the false alarm in urban building change detection is proposed in this paper. Firstly, as shadows casted by urban buildings are of distinct spectral and shape feature, it adopts a supervised object-based classification technique to extract them in this paper. Secondly, on the opposite direction of sunlight illumination, a straight line is drawn along the principal orientation of building in every extracted shadow region. Starting from the straight line and moving toward the sunlight direction, a rectangular area is constructed to cover partial shadow and rooftop of each building. Thirdly, an algebra and geometry invariant based method is used to abstract the spatial topological relationship of the potential unchanged buildings from all central points of the rectangular area. Finally, based on an oriented texture curvature descriptor, an index is established to determine the actual false alarm in building change detection result. The experiment results validate that the proposed method can be used as an effective framework to alleviate the false alarm in building change detection from urban VHR image.
35
Chen, J., J. L. Hou, and M. Deng. "AN APPROACH TO ALLEVIATE THE FALSE ALARM IN BUILDING CHANGE DETECTION FROM URBAN VHR IMAGE." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (June 21, 2016): 459–65. http://dx.doi.org/10.5194/isprs-archives-xli-b7-459-2016.
Анотація:
Building change detection from very-high-resolution (VHR) urban remote sensing image frequently encounter the challenge of serious false alarm caused by different illumination or viewing angles in bi-temporal images. An approach to alleviate the false alarm in urban building change detection is proposed in this paper. Firstly, as shadows casted by urban buildings are of distinct spectral and shape feature, it adopts a supervised object-based classification technique to extract them in this paper. Secondly, on the opposite direction of sunlight illumination, a straight line is drawn along the principal orientation of building in every extracted shadow region. Starting from the straight line and moving toward the sunlight direction, a rectangular area is constructed to cover partial shadow and rooftop of each building. Thirdly, an algebra and geometry invariant based method is used to abstract the spatial topological relationship of the potential unchanged buildings from all central points of the rectangular area. Finally, based on an oriented texture curvature descriptor, an index is established to determine the actual false alarm in building change detection result. The experiment results validate that the proposed method can be used as an effective framework to alleviate the false alarm in building change detection from urban VHR image.
36
Li, Hao-xiang, María Rosendo-López, Yi-fan Zhu, Xu-dong Fan, Daniel Torrent, Bin Liang, Jian-chun Cheng, and Johan Christensen. "Ultrathin Acoustic Parity-Time Symmetric Metasurface Cloak." Research 2019 (August 19, 2019): 1–7. http://dx.doi.org/10.34133/2019/8345683.
Анотація:
Invisibility or unhearability cloaks have been made possible by using metamaterials enabling light or sound to flow around obstacle without the trace of reflections or shadows. Metamaterials are known for being flexible building units that can mimic a host of unusual and extreme material responses, which are essential when engineering artificial material properties to realize a coordinate transforming cloak. Bending and stretching the coordinate grid in space require stringent material parameters; therefore, small inaccuracies and inevitable material losses become sources for unwanted scattering that are decremental to the desired effect. These obstacles further limit the possibility of achieving a robust concealment of sizeable objects from either radar or sonar detection. By using an elaborate arrangement of gain and lossy acoustic media respecting parity-time symmetry, we built a one-way unhearability cloak able to hide objects seven times larger than the acoustic wavelength. Generally speaking, our approach has no limits in terms of working frequency, shape, or size, specifically though we demonstrate how, in principle, an object of the size of a human can be hidden from audible sound.
37
Goggin, Gerard, and Karen Soldatić. "Automated decision-making, digital inclusion and intersectional disabilities." New Media & Society 24, no. 2 (February 2022): 384–400. http://dx.doi.org/10.1177/14614448211063173.
Анотація:
Disability is a long-standing area of digital inclusion finally emerging out of the shadows. In this article, we argue that a critical understanding of digital media from the perspectives of disability and intersectionality will offer generative insights for framing the terms and agenda of digital inclusion in the next decade. With a focus on the area of automated decision-making (ADM) in social and welfare services, we reflect upon the controversial 2015–2020 Australian government programme widely known as ‘Robodebt’ that recovers putative debts from support recipients – and we discuss implications for Indigenous Australians with disabilities in particular. We contrast the ‘Robodebt’ programme with explicit digital inclusion policy on disability in Australia, noting that such digital inclusion policy does not specifically acknowledge yet alone address ADM or other aspects of automation. Here, there is a major opportunity for overdue acknowledgement of disability and intersectionality to spur and shape an affirmative and just agenda on people with disabilities’ digital inclusion, ADM and other associated areas of automated technologies.
38
Wang, Yanjun, Shaochun Li, Yunhao Lin, and Mengjie Wang. "Lightweight Deep Neural Network Method for Water Body Extraction from High-Resolution Remote Sensing Images with Multisensors." Sensors 21, no. 21 (November 7, 2021): 7397. http://dx.doi.org/10.3390/s21217397.
Анотація:
Rapid and accurate extraction of water bodies from high-spatial-resolution remote sensing images is of great value for water resource management, water quality monitoring and natural disaster emergency response. For traditional water body extraction methods, it is difficult to select image texture and features, the shadows of buildings and other ground objects are in the same spectrum as water bodies, the existing deep convolutional neural network is difficult to train, the consumption of computing resources is large, and the methods cannot meet real-time requirements. In this paper, a water body extraction method based on lightweight MobileNetV2 is proposed and applied to multisensor high-resolution remote sensing images, such as GF-2, WorldView-2 and UAV orthoimages. This method was validated in two typical complex geographical scenes: water bodies for farmland irrigation, which have a broken shape and long and narrow area and are surrounded by many buildings in towns and villages; and water bodies in mountainous areas, which have undulating topography, vegetation coverage and mountain shadows all over. The results were compared with those of the support vector machine, random forest and U-Net models and also verified by generalization tests and the influence of spatial resolution changes. First, the results show that the F1-score and Kappa coefficients of the MobileNetV2 model extracting water bodies from three different high-resolution images were 0.75 and 0.72 for GF-2, 0.86 and 0.85 for Worldview-2 and 0.98 and 0.98 for UAV, respectively, which are higher than those of traditional machine learning models and U-Net. Second, the training time, number of parameters and calculation amount of the MobileNetV2 model were much lower than those of the U-Net model, which greatly improves the water body extraction efficiency. Third, in other more complex surface areas, the MobileNetV2 model still maintained relatively high accuracy of water body extraction. Finally, we tested the effects of multisensor models and found that training with lower and higher spatial resolution images combined can be beneficial, but that using just lower resolution imagery is ineffective. This study provides a reference for the efficient automation of water body classification and extraction under complex geographical environment conditions and can be extended to water resource investigation, management and planning.
39
Jang, Seok-Woo. "Environmental Factor-Based Segmentation of Images in Natural Environments." Journal of Computational and Theoretical Nanoscience 18, no. 5 (May 1, 2021): 1566–71. http://dx.doi.org/10.1166/jctn.2021.9583.
Анотація:
The robust segmentation of color images in a natural environment without specific constraints such as lighting or background is very important in the field of image processing and computer vision. In this paper, an environmentally adaptive image segmentation method using color invariant is proposed. The proposed method introduces a number of color invariant, such as W, C, U, N, and H, and automatically detects factors in the surrounding environment in which images such as lighting, shading, and highlights are taken. The image is then effectively split based on the edge by selecting the color invariant optimal for the detected environmental factors. In the experiment, we implemented the proposed edge-based image segmentation algorithm. Various image data taken in general environments without specific constraints were utilized as input images of the suggested system. In this study, various kinds of color images taken in different environments were tested, and each color invariant was extracted from the experiments that best expressed the environmental changes around them. As a result, a largest number of images were determined to have a change in the intensity of lighting, followed by highlights and shadows. In addition, there were a few images that determined that no special state environmental changes existed. As the results of the experiment show visually, the existing method did not correctly remove shadows and did not detect some areas of the circular shape. In addition, the existing method can also be found to be partially inaccurate in edge detection in many areas. On the other hand, the proposed method confirmed stable segmentation of images. The proposed color invariant-based image segmentation algorithm is expected to be useful in various pattern recognition areas such as face tracking, mobile object detection, gesture recognition, motion understanding, etc.
40
Jang, Seok-Woo. "Environmental Factor-Based Segmentation of Images in Natural Environments." Journal of Computational and Theoretical Nanoscience 18, no. 5 (May 1, 2021): 1566–71. http://dx.doi.org/10.1166/jctn.2021.9583.
Анотація:
The robust segmentation of color images in a natural environment without specific constraints such as lighting or background is very important in the field of image processing and computer vision. In this paper, an environmentally adaptive image segmentation method using color invariant is proposed. The proposed method introduces a number of color invariant, such as W, C, U, N, and H, and automatically detects factors in the surrounding environment in which images such as lighting, shading, and highlights are taken. The image is then effectively split based on the edge by selecting the color invariant optimal for the detected environmental factors. In the experiment, we implemented the proposed edge-based image segmentation algorithm. Various image data taken in general environments without specific constraints were utilized as input images of the suggested system. In this study, various kinds of color images taken in different environments were tested, and each color invariant was extracted from the experiments that best expressed the environmental changes around them. As a result, a largest number of images were determined to have a change in the intensity of lighting, followed by highlights and shadows. In addition, there were a few images that determined that no special state environmental changes existed. As the results of the experiment show visually, the existing method did not correctly remove shadows and did not detect some areas of the circular shape. In addition, the existing method can also be found to be partially inaccurate in edge detection in many areas. On the other hand, the proposed method confirmed stable segmentation of images. The proposed color invariant-based image segmentation algorithm is expected to be useful in various pattern recognition areas such as face tracking, mobile object detection, gesture recognition, motion understanding, etc.
41
Adeline, Karine R. M., Xavier Briottet, Sidonie Lefebvre, Nicolas Rivière, Jean-Philippe Gastellu-Etchegorry, and Fabrice Vinatier. "Impact of Tree Crown Transmittance on Surface Reflectance Retrieval in the Shade for High Spatial Resolution Imaging Spectroscopy: A Simulation Analysis Based on Tree Modeling Scenarios." Remote Sensing 13, no. 5 (March 2, 2021): 931. http://dx.doi.org/10.3390/rs13050931.
Анотація:
With the advancement of high spatial resolution imaging spectroscopy, an accurate surface reflectance retrieval is needed to derive relevant physical variables for land cover mapping, soil, and vegetation monitoring. One challenge is to deal with tree shadows using atmospheric correction models if the tree crown transmittance Tc is not properly taken into account. This requires knowledge of the complex radiation mechanisms that occur in tree crowns, which can be provided by coupling the physical modeling of canopy radiative transfer codes (here DART) and the 3D representations of trees. First in this study, a sensitivity analysis carried out on DART simulations with an empirical 3D tree model led to a statistical regression predicting Tc from the tree leaf area index (LAI) and the solar zenith angle with good performances (RMSE ≤ 4.3% and R2 ≥ 0.91 for LAI ≤ 4 m2.m−2). Secondly, more realistic 3D voxel-grid tree models derived from terrestrial LiDAR measurements over two trees were considered. The comparison of DART-simulated Tc from these models with the previous predicted Tc over 0.4–2.5 µm showed three main sources of inaccuracy quoted in order of importance: (1) the global tree geometry shape (mean bias up to 21.5%), (2) the transmittance fraction associated to multiple scattering, Tscat (maximum bias up to 13%), and (3) the degree of realism of the tree representation (mean bias up to 7.5%). Results showed that neglecting Tc leads to very inaccurate reflectance retrieval (mean bias > 0.04), particularly if the background reflectance is high, and in the near and shortwave infrared – NIR and SWIR – due to Tscat. The transmittance fraction associated to the non-intercepted transmitted light, Tdir, can reach up to 95% in the SWIR, and Tscat up to 20% in the NIR. Their spatial contributions computed in the tree shadow have a maximum dispersion of 27% and 8% respectively. Investigating how to approximate Tdir and Tscat spectral and spatial variability along with the most appropriate tree 3D modeling is crucial to improve reflectance retrieval in tree shadows when using atmospheric correction models.
42
Qu, Shenming, Huafei Zhou, Bo Zhang, and Shengbin Liang. "MSPNet: Multi-Scale Strip Pooling Network for Road Extraction from Remote Sensing Images." Applied Sciences 12, no. 8 (April 18, 2022): 4068. http://dx.doi.org/10.3390/app12084068.
Анотація:
Extracting roads from remote sensing images can support a range of geo-information applications. However, it is challenging due to factors such as the complex distribution of ground objects and occlusion of buildings, trees, shadows, etc. Pixel-wise classification often fails to predict road connectivity and thus produces fragmented road segments. In this paper, we propose a multi-scale strip pooling network (MSPNet) to learn the linear features of roads. Motivated by the strip pooling being more aligned with the shape of roads, which are long-span and narrow, we develop a multi-scale strip pooling (MSP) module that utilizes strip pooling layers with long but narrow kernel shapes to capture multi-scale long-range context from horizontal and vertical directions. The proposed MSP module focuses on establishing relationships along the road region to guarantee the connectivity of roads. Considering the complex distribution of ground objects, the spatial pyramid pooling is applied to enhance the learning ability of complex features in different sub-regions. In addition, to alleviate the problem caused by an imbalanced distribution of road and non-road pixels, we use binary cross-entropy and dice-coefficient loss functions to jointly train our proposed deep learning model. Then, we perform ablation experiments to adjust the loss contributions to suit the task of road extraction. Comparative experiments on a popular benchmark DeepGlobe dataset demonstrate that our proposed MSPNet establishes new competitive results in both IoU and F1-score.
43
Yuan, Hua, Robert E. Dickinson, Yongjiu Dai, Muhammad J. Shaikh, Liming Zhou, Wei Shangguan, and Duoying Ji. "A 3D Canopy Radiative Transfer Model for Global Climate Modeling: Description, Validation, and Application." Journal of Climate 27, no. 3 (January 24, 2014): 1168–92. http://dx.doi.org/10.1175/jcli-d-13-00155.1.
Анотація:
Abstract The process of solar radiative transfer at the land surface is important to energy, water, and carbon balance, especially for vegetated areas. Currently the most commonly used two-stream model considers the plant functional types (PFTs) within a grid to be independent of each other and their leaves to be horizontally homogeneous. This assumption is unrealistic in most cases. To consider canopy three-dimensional (3D) structural effects, a new framework of 3D canopy radiative transfer model was developed and validated by numerical simulations and shows a good agreement. A comparison with the two-stream model in the offline Community Land Model (CLM4.0) shows that an increase of canopy absorption mainly happens with sparse vegetation or with multilayer canopies with a large sun zenith angle θsun and is due to increases of the ground and sky shadows and of the optical pathlength because of the shadow overlapping between bushes and canopy layers. A decrease of canopy absorption occurs in densely vegetated areas with small θsun. For a one-layer canopy, these decreases are due to crown shape effects that enhance the transmission through the canopy edge. For a multilayer canopy, aside from these shape effects, transmission is also increased by the decreased ground shadow due to the shadow overlapping between layers. Ground absorption usually changes with opposite sign as that of the canopy absorption. Somewhat lower albedos are found over most vegetated areas throughout the year. The 3D model also affects the calculation of the fraction of sunlit leaves and their corresponding absorption.
44
Nagano, Mikinori, Fumiya Yamaga, Dai Yamazaki, Ryuji Maruyama, Kauhiko Soyama, and Kazuya Yamamura. "Quadruple Stacked Elliptical Supermirror Device for One Dimensional Neutron Focusing." Key Engineering Materials 523-524 (November 2012): 272–75. http://dx.doi.org/10.4028/www.scientific.net/kem.523-524.272.
Анотація:
Focusing neutron beam with wide wavelength range is an indispensable technique used to compensate for weak signals from tiny samples in various experiments using pulsed neutron beam generated from high intensity proton accelerator facilities, such as J-PARC. Aspherical supermirror device is one of the most effective optical devices for focusing neutron beam with wide wavelength range since it has no chromatic aberration. Stack of aspherical supermirror enables us to focus neutron beams with wide divergence. Thin mirrors with a millimeter thickness are required to minimize the absorption loss of incident neutron beams since the thickness of a mirror shadows the reflective area of the other mirrors. Previously, we developed a fabrication process of a precise millimeter-thick elliptical supermirror. This process consists of noncontact figuring by the numerically controlled local wet etching technique, the finishing of surface without degrading mirror shape by low-pressure polishing, and the ion beam sputter deposition of NiC/Ti multilayers on both sides of the mirror substrate to compensate for film stress. In this paper, we report fabrication of elliptical supermirror with a thickness of 1 mm and development of multiply-arranged neutron focusing mirror device using stacked 4 fabricated elliptical supermirror with a thickness of 1mm.
45
Chapman, Hazel, Norbert J. Cordeiro, Paul Dutton, Dan Wenny, Shumpei Kitamura, Beth Kaplin, Felipe P. L. Melo, and Michael J. Lawes. "Seed-dispersal ecology of tropical montane forests." Journal of Tropical Ecology 32, no. 5 (August 3, 2016): 437–54. http://dx.doi.org/10.1017/s0266467416000389.
Анотація:
Abstract:Seed-dispersal ecology in tropical montane forests (TMF) differs in some predictable ways from tropical lowland forests (TLF). Environmental, biogeographic and biotic factors together shape dispersal syndromes which in turn influence forest structure and community composition. Data on diaspore traits along five elevational gradients from forests in Thailand, the Philippines, Tanzania, Malawi and Nigeria showed that diaspore size decreases with increasing altitude, fleshy fruits remain the most common fruit type but the relative proportion of wind-dispersed diaspores increases with altitude. Probably corresponding to diaspore size decreasing with increasing elevation, we also provide evidence that avian body size and gape width decrease with increasing altitude. Among other notable changes in the frugivorous fauna across elevational gradients, we found quantitative evidence illustrating that the proportion of bird versus mammalian frugivores increases with altitude, while TMF primates decrease in diversity and density, and switch diets to include less fruit and more leaf proportionately. A paucity of studies on dispersal distance and seed shadows, the dispersal/predation balance and density-dependent mortality thwart much-needed conclusive comparisons of seed dispersal ecology between TMF and TLF, especially from understudied Asian forests. We examine the available evidence, reveal knowledge gaps and recommend research to enhance our understanding of seed dispersal ecology in tropical forests. This review demonstrates that seed dispersal is a more deterministic and important process in tropical montane forests than has been previously appreciated.
46
Ma, Weixuan, Youchuan Wan, Jiayi Li, Sa Zhu, and Mingwei Wang. "An Automatic Morphological Attribute Building Extraction Approach for Satellite High Spatial Resolution Imagery." Remote Sensing 11, no. 3 (February 8, 2019): 337. http://dx.doi.org/10.3390/rs11030337.
Анотація:
A new morphological attribute building index (MABI) and shadow index (MASI) are proposed here for automatically extracting building features from very high-resolution (VHR) remote sensing satellite images. By investigating the associated attributes in morphological attribute filters (AFs), the proposed method establishes a relationship between AFs and the characteristics of buildings/shadows in VHR images (e.g., high local contrast, internal homogeneity, shape, and size). In the pre-processing step of the proposed work, attribute filtering was conducted on the original VHR spectral reflectance data to obtain the input, which has a high homogeneity, and to suppress elongated objects (potential non-buildings). Then, the MABI and MASI were calculated by taking the obtained input as a base image. The dark buildings were considered separately in the MABI to reduce the omission of the dark roofs. To better detect buildings from the MABI feature image, an object-oriented analysis and building-shadow concurrence relationships were utilized to further filter out non-building land covers, such as roads and bare ground, that are confused for buildings. Three VHR datasets from two satellite sensors, i.e., Worldview-2 and QuickBird, were tested to determine the detection performance. In view of both the visual inspection and quantitative assessment, the results of the proposed work are superior to recent automatic building index and supervised binary classification approach results.
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Erkelens, Casper J. "Perspective on Canaletto’s Paintings of Piazza San Marco in Venice." Art and Perception 8, no. 1 (March 4, 2020): 49–67. http://dx.doi.org/10.1163/22134913-20191131.
Анотація:
Perspective plays an important role in the creation and appreciation of depth on paper and canvas. Paintings of extant scenes are interesting objects for studying perspective, because such paintings provide insight into how painters apply different aspects of perspective in creating highly admired paintings. In this regard the paintings of the Piazza San Marco in Venice by Canaletto in the eighteenth century are of particular interest because of the Piazza’s extraordinary geometry, and the fact that Canaletto produced a number of paintings from similar but not identical viewing positions throughout his career. Canaletto is generally regarded as a great master of linear perspective. Analysis of nine paintings shows that Canaletto almost perfectly constructed perspective lines and vanishing points in his paintings. Accurate reconstruction is virtually impossible from observation alone because of the irregular quadrilateral shape of the Piazza. Use of constructive tools is discussed. The geometry of Piazza San Marco is misjudged in three paintings, questioning their authenticity. Sizes of buildings and human figures deviate from the rules of linear perspective in many of the analysed paintings. Shadows are stereotypical in all and even impossible in two of the analysed paintings. The precise perspective lines and vanishing points in combination with the variety of sizes for buildings and human figures may provide insight in the employed production method and the perceptual experience of a given scene.
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Baranov, Dmitry. "DEPERSONALIZED OBJECTS: PARADOXES OF ETHNOGRAPHIC COLLECTIONS." Antropologicheskij forum 16, no. 47 (December 2020): 113–36. http://dx.doi.org/10.31250/1815-8870-2020-16-47-113-136.
Анотація:
In ethnographic studies of material culture, things are described primarily as signs of social phenomena; but things themselves remain in the shadows. Even when it comes to museum research, a material object is considered either as an element of the classification series, or as an example of the manufacturing and living techniques in the local tradition, or as a representative of the cultural contexts from which it was removed. The very collection format of museum storage hides the uniqueness of a thing, because the collection is not able to accommodate its singular nature, since each thing is really a “universe of individuality”. The article examines possible ways for museum ethnography to go beyond its inherent anonymous and depersonalizing discourse. As an alternative to the latter, a “biographical” focus is proposed, which allows one to see subjectivity and individuality in things. The uniqueness of a thing is manifested not only in its biography, but also in its very materiality: material, shape, design, texture, color, weight, smell, etc. The close attention of the ethnographic museum to specific objects and the people to whom they belonged makes it possible to highlight those details and particulars, without which it is impossible to understand culture as a whole.
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Tian, Qiuyue, Qiang Liu, Jie Guang, Leiku Yang, Hanwei Zhang, Cheng Fan, Yahui Che, and Zhengqiang Li. "The Estimation of Surface Albedo from DSCOVR EPIC." Remote Sensing 12, no. 11 (June 11, 2020): 1897. http://dx.doi.org/10.3390/rs12111897.
Анотація:
Surface albedo is an important parameter in climate models. The main way to obtain continuous surface albedo for large areas is satellite remote sensing. However, the existing albedo products rarely meet daily-scale requirements, which has a large impact on climate change research and rapid dynamic changes of surface analysis. The Earth Polychromatic Imaging Camera (EPIC) on the Deep Space Climate Observatory (DSCOVR) platform, which was launched into the Sun–Earth’s first Lagrange Point (L1) orbit, can provide spectral images of the entire sunlit face of Earth with 10 narrow channels (from 317 to 780 nm). As EPIC can provide high-temporal resolution data, it is beneficial to explore the feasibility of EPIC to estimate high-temporal resolution surface albedo. In this study, hourly surface albedo was calculated based on EPIC observation data. Then, the estimated albedo results were validated by ground-based observations of different land cover types. The results show that the EPIC albedo is basically consistent with the trend of the ground-based observations in the whole time series variation. The diurnal variation of the surface albedo from the hourly EPIC albedo exhibits a “U” shape curve, which has the same trend as the ground-based observations. Therefore, EPIC is helpful to enhance the temporal resolution of surface albedo to diurnal. Surfaces with a three-dimensional structure that casts shadows display the hotspot effect, producing a reflectance peak in the retro-solar direction and lower reflectance at viewing angles away from the solar direction. DSCOVR observes the entire sunlit face of the Earth, which is helpful to make up for the deficiency in the observations of traditional satellites in the hotspot direction in bidirectional reflectance distribution function (BRDF) research, and can help to improve the underestimation of albedo in the direction of hotspot observation.
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Çöltekin, Arzu, Gianna Hartung, and Martina Meyer. "Deconstructing the relief inversion effect: Contributors of the problem and its solutions." Abstracts of the ICA 1 (July 15, 2019): 1–2. http://dx.doi.org/10.5194/ica-abs-1-48-2019.
Анотація:
<p><strong>Abstract.</strong> <i>Terrain reversal</i> (also known as <i>relief inversion</i>) effect is a common and well-known illusion encountered in shaded relief maps and satellite imagery where the main depth cue is shading/shadows (Imhof, 1967; Bernabe-Poveda, Callejo, & Ballari, 2005; Saraf, Das, Agarwal, & Sundaram, 1996; Biland & Çöltekin, 2016; Çöltekin, Rautenbach, Coetzee, & Mokwena, 2018). This illusion interferes with our perception of <i>shape from shading</i> (e.g., see Kleffner & Ramachandran, 1992; Prados & Faugeras, 2006). If the light shines from below, the shadows are then above, and this conflicts with the human mind’s ‘unconscious statistics’, that is, our minds assume that the light is more or less always above. This cognitive phenomenon is termed <i>light from above prior</i> (Kleffner & Ramachandran, 1992). When the prior is violated, we see three-dimensional (3D) shapes ambiguously, or inverted; such that a valley looks like a ridge in a terrain representation and vice versa (Bernabé-Poveda, Sánchez-Ortega, & Çöltekin, 2011; Bernabé-Poveda & Çöltekin, 2014). In a recent study, we demonstrated that adding texture and color as opposed to the shading alone (as in the shaded relief maps) affect 3D shape identification performance (Çöltekin & Biland, 2018). More precisely, when texture is present, success rates are higher in correctly identifying valleys and ridges, as well as other 3D spatial relationships. This is possibly a result of interpreting the spatial relationships between terrain features because people can recognize them more easily (e.g., a river is easier to identify on a photo than on a shaded relief map). Somewhat surprisingly, we also observed that people are better with 3D shape identification with grayscale images than with the color images; which we interpreted as the result of more pronounced contrast in grayscale images (Çöltekin & Biland, 2018). Because we see that presence of other visual cues do interfere with the relief inversion effect, in this study, we explore other additional factors (depth cues, labels, terrain types, task types, expertise levels and spatial abilities) that may contribute to, or alleviate, the relief inversion effect. Understanding how other factors contribute to the strength of the illusion can help develop better-informed use of the displays that contain this illusion and lead to better solutions. In this vein, in a series of experiments, we examined effects of stereoscopic viewing vs. monoscopic viewing, terrain types (highly rugged vs. subtly rugged), task types (3D shape identification vs. land cover identification; simple vs. complex), expertise levels, and spatial abilities. In a second experiment, we examined how well various solutions function for correcting the illusion in various combinations of variables (labels, motion, stereo). Figure 1 shows an example of the shape identification tasks used in the first study.</p><p>We are developing full papers reporting the effects of each tested factor in detail, which would be beyond the scope of this short paper. In this short paper, we focus on the effects of stereo on the strength of the relief inversion experience (does showing the terrain in stereo make the relief inversion effect stronger or weaker?), and on the solutions for satellite images (if we combine a ‘solution’ with stereo viewing, do shape perception and land cover identification success improve?). The second question, especially the mention of land cover identification, is related to the fact that a common solution to terrain reversal effect is to overlay a semi-transparent shaded relief map (SRM overlay) on top of the image that has the perceptual problem (Bernabé-Poveda, Sánchez-Ortega, & Çöltekin, 2011; Saraf, Das, Agarwal, & Sundaram, 1996b).</p><p> Our initial findings suggest that stereo viewing does help against the issues in 3D shape perception; although it does not entirely remove it: 3D shape perception accuracy is &sim;15% with original images, &sim;32% with the stereo. When stereoscopic viewing is combined with an SRM overlay solution, it improves the 3D shape perception: 3D shape perception accuracy with the SRM overlay solution alone is &sim;40%, with added stereo &sim;68%, but impairs the land cover identification (accuracy is &sim;78% with the SRM overlay, and drops to &sim;44% when stereo is added). These findings are based on two controlled experiments with 33 and 35 participants respectively, and the differences are statistically significant based on analysis of variance (<i>p</i>&thinsp;&lt;&thinsp;0.05). We believe the impairment of the land cover identification is linked to the stereoscopic viewing method, as the tests were conducted with anaglyph stereo, where color perception is strongly affected. These observations, taken together, provide us the initial clues that providing the viewers with an additional depth cue (in this case stereopsis) is indeed helpful; but also suggest that the success of the solution depends on how it is implemented, and the nature of the task; for example, if color is important for the task or not.</p><p> We believe our findings are of key importance in understanding the relief inversion effect, and its future solutions, and will guide cartographers towards a more nuanced comprehension and work practices.</p></p>