Use Of Shadow Research Articles

Use of shadows for extracting buildings in aerial images

Two new methods integrating region growing and edge detection are presented to extract buildings in aerial images. In the domain we are considering, building shadows play an important role in enhancing the detection accuracy and reliability. In both methods, interpretations of buildings are only based on the reliable features (shadows and shapes of buildings in our case) obtained by segmentation and are not affected by artifacts or sementation errors. We also propose algorithms to correct the segmentation errors or to enhance resultant contours based on local edge information (contrast and smoothness along contours) and global shape information. In the first method we start with an edge detection to loacte shadowed boundaries, then combine region growing to find boundaries without shadows. In the second method, we use region growing to obtain a primary segmentation. Edge information is then used to eliminate false boundaries or to modify the contours. Further modification of contour artifacts can be achieved by using domain knowledge (most boundaries are smooth enough to be approximated by straight segments.)

Use of shadows for extracting buildings in aerial images

Use of shadows for extracting buildings in aerial images

Neolithic Blind Statues and Balkan Folklore of the Blind

PREHISTORIC representations of divinities present some problems and phenomena which have not been sufficiently scientifically analysed and understood. This group includes certain blind statues (idols) of the Neolithic epoch of the Central Balkans. We shall try to analyse them from a paleoethnological point of view, and draw comparisons with the attitude towards blindness in modern Balkan folklore. Blind idols of the Neolithic epoch in the Central Balkans, as far as we know, mostly originate from Kosovo and especially Titova Mitrovica (sites Karagai at itkovac, and Fafos), and from the Pavlovac site in South Serbia. One statue of a blind idol or god was found on the Karagac site at Titova Mitrovica (Figure 1). It was made in a naturalistic-realistic style, and its realistically shaped head has the following characteristics: blunt nose with wide nostrils; wide, open mouth; eyes sunken into their sockets; top and back of the head slightly gnarled; broad, oval chin. The whole face is oval and long, and this is the statue of an old blind person, with wide forehead and without modelled ears. It has a strong neck.' Archaeologists give special importance to this statue; among other things, it has been pointed out that this terracotta is an example of the best free realistic style in the Neolithic Age in the Balkans. Its head is modelled with 'a surprising freedom unique in prehistoric art' of this area, with no flat surface, 'since the whole mass moves freely and is very elastic.' The basic structure of the head, with eyebrow arches, eye sockets, cheekbones and jaws, is of primary importance, and all other details are subordinate to it. Special effects of light and dark were achieved by the sculptor. This use of shadows represents impressionistic characteristics in this statue from Karagac. The blind statue from Fafos site at Titova Mitrovica (Figure 2) is of similar naturalistic-realistic style, and has the following features: neck, chin, open mouth, nose with formed nostrils, cheekbones slightly fallen in, small eyes sunken in their sockets and with visible eyelids, medium forehead, one partially formed ear, and hair covering the top and back of the head; this starts from the top of the forehead up to the half of the top of the head, where it is separated by a wreath from the second part of the hair, spreading vertically over the whole head and framing the face and the back of the head to the neck. The statue is made of terracotta in various colours: grey, dark grey, reddish, and sooty on the face. At Neolithic sites at Pavlovac in South Serbia, statuettes of the blind were discovered by chance. They were heads and torsos of both men and women, mainly in naturalistic-realistic style. They have a realistic-looking neck and chin, but they have no mouth, and the nose is without nostrils; the cheekbones are slightly fallen in; the eye-sockets are small and fallen in, and are more strongly marked on the male than on the female statuettes, with eyebrows and eyelids clearly formed; medium forehead; the top and back of the head are covered by hair. One, the statuette of a blind woman, shows the following anthropological elements: nose, fallen-in eyes placed almost under nose, hair covering top and back of the head. One blind statuette made of fine, pure terracotta, representing a blind goddess with a long oval face with no mouth, is the one we would like to point out (Figure 3). It is a

The Visualization of Rotation in Diagrams of Three-Dimensional Structures

Two experiments were carried out to investigate how remedial instruction may be given to students who have difficulties in visualizing the diagrammatic representation of a three-dimensional structure after the structure has been rotated. Experiment I demonstrated that two methods using models and diagrams were significantly better than a method that used only diagrams. The use of shadows with the models was significantly better than the use of models on their own. Experiment II investigated different ways of presenting a sequence of slides to demonstrate how the diagrams should be drawn to show changes in the diagrams as the structure rotates through small angles. The more effective method of changing the slides was one in which successive projected images dissolved into each other. The effectiveness of the programmes increased as the angle, through which the structure rotated for successive slides, decreased from 30° to 10°.

The Visualization of Rotation in Diagrams of Three-Dimensional Structures

Two experiments were carried out to investigate how remedial instruction may be given to students who have difficulties in visualizing the diagrammatic representation of a three-dimensional structure after the structure has been rotated. Experiment I demonstrated that two methods using models and diagrams were significantly better than a method that used only diagrams. The use of shadows with the models was significantly better than the use of models on their own. Experiment II investigated different ways of presenting a sequence of slides to demonstrate how the diagrams should be drawn to show changes in the diagrams as the structure rotates through small angles. The more effective method of changing the slides was one in which successive projected images dissolved into each other. The effectiveness of the programmes increased as the angle, through which the structure rotated for successive slides, decreased from 30° to 10°.

Atmospheric effects in satellite imaging of mountainous terrain

It is possible to obtain useful maps of surface albedo from remotely sensed images by eliminating effects due to topography and the atmosphere, even when the atmospheric state is not known. A simple phenomenological model of earth radiance that depends on six empirically determined parameters is developed given certain simplifying assumptions. The model incorporates path radiance and illumination from sun and sky and their dependencies on surface altitude and orientation. It takes explicit account of surface shape, represented by a digital terrain model, and is therefore especially suited for use in mountainous terrain. A number of ways of determining the model parameters are discussed, including the use of shadows to obtain path radiance and to estimate local albedo and sky irradiance. The emphasis is on extracting as much information from the image as possible, given a digital terrain model of the imaged area and a minimum of site-specific atmospheric data. The albedo image, introduced as a representation of surface reflectance, provides a useful tool to evaluate the simple imaging model. Criteria for the subjective evaluation of albedo images are established and illustrated for Landsat multispectral data of a mountainous region of Switzerland. The method exposes some of the limitations found in computing reflectance information using only the image-forming equation.

A Second Generation Color Tube Providing More than Twice the Brightness and Improved Contrast

The parallax or shadow-mask type of tri-color tube was first described in the literature with a line-or grille-type color selection electrode1 but it first saw the light of commercial day in very much like its present form, using an apertured plate2 or mask for color selection. As thus introduced, the tube was distinctly wanting in brightness due principally to the poor electron-transmissivity of the aperture mask and efforts have been made ever since to improve its brightness capability. For the most part, emphasis has been placed on better tube fabricating techniques, which make possible the use of shadow mask structures having a higher electron transparency, and on new phosphor materials which yield brighter pictures in response to electron excitation. Even in its present commercial form, however, the shadow mask tube has not attained the desirable level of brightness, that is to say, sufficient for use in environments of high light ambients such as well lighted retail stores and similar display rooms, porches or rooms of residences that have large window areas and the like. When operated in such locations, the shadow mask tube as it has been known heretofore suffers a serious loss in performance; specifically, the picture washes out both in respect of contrast and chroma.

Use of Shadows for Studying the Three-Dimensional Structure of Insect Swarms12

A photographic technique is described for determining the three-dimensional position of swarming midges. The procedure is applied to the midge, Anarete pritchardi Kim, which swarms in the daytime, preferably under clear skies 3–5 cm above a white surface or a swarm marker. The midges cast their shadows on the marker, and the shadow combined with midge's real image on film can be used to estimate the height of the flying insect.

Digital image processing techniques to extract metric data on buildings from shadows on simulated air photos

This paper investigates the use of shadows on aerial photographs to obtain ground parameters (length, width, height, area and volume) of buildings by image processing techniques. The assumptions of the flat ground and true vertical photography are made in the study, and the investigation is performed on a scale model of an urban environment. Only the case of separate shadows is examined, and no attempt is made to deal with the cases of overlapping shadows and shadows falling on other buildings. The numerical values of the building parameters obtained by image processing are compared with the corresponding “true” values measured directly on the scale model and a statistical error analysis is performed. The presence of a systematic error is detected in the height and volume residuals. A working model, based upon regression analysis, is suggested for use with actual aerial photographs.

The Determination of National Housing Policies

the social marginal productivity is the highest.2 The estimation of social marginal productivity requires value judgments concerning various social objectives, and the use of shadow prices t The author acknowledges the financial assistance of the Institute for International Studies which made possible the basic research for this study, which was conducted in Santiago, Chile, in 1965. Typing and editorial assistance were provided by the Center for Real Estate and Urban Economics. Octavio Cabello at the Economic Commission for Latin America, Santiago, Chile, aided the author in manifold ways during his residence in Santiago in the Spring of 1965. Robert Dorfman, Visiting Research Professor at the University of California, Berkeley, offered a number of particularly incisive comments and suggestions on an earlier draft. Carlos Frankenhoff, Lowden Wingo, Albert H. Schaaf, Roland Artle, and others also reviewed early drafts of the manuscript. Richard Recht and Stanley Hamilton of the Center for Real Estate and Urban Economics assisted in reviewing the mathematical notation and suggesting changes in the final draft. Mr. Hamilton assisted the author in the revision of an earlier draft. A more detailed version of this article was published in Italian in the Rivista Internazionale, Milan, Italy, November 1967. * Professor of Finance and Chairman of the Center for

A Second Generation Color Tube Providing More Than Twice the Brightness and Improved Contrast

The parallax or shadow-mask type of tri-color tube was first described in the literature with a line-or grille-type color selection electrode1 but it first saw the light of commercial day in very much like its present form, using an apertured plate2 or mask for color selection. As thus introduced, the tube was distinctly wanting in brightness due principally to the poor electron-transmissivity of the aperture mask and efforts have been made ever since to improve its brightness capability. For the most part, emphasis has been placed on better tube fabricating techniques, which make possible the use of shadow mask structures having a higher electron transparency, and on new phosphor materials which yield brighter pictures in response to electron excitation. Even in its present commercial form, however, the shadow mask tube has not attained the desirable level of brightness, that is to say, sufficient for use in environments of high light ambients such as well lighted retail stores and similar display rooms, porches or rooms of residences that have large window areas and the like. When operated in such locations the shadow mask tube as it has been known heretofore suffers a serious loss in performance; specifically, the picture washes out both in respect of contrast and chroma.