Gravity as a Monocular Cue for Perception of Absolute Distance and/or Absolute Size

Perception ◽  
1992 ◽  
Vol 21 (1) ◽  
pp. 69-76 ◽  
Author(s):  
John S Watson ◽  
Martin S Banks ◽  
Claes von Hofsten ◽  
Constance S Royden
Keyword(s):  
Wave Motion ◽  
Moving Objects ◽  
Formal Analysis ◽  
Free Fall ◽  
Absolute Distance ◽  
Absolute Size ◽  
The Absolute ◽  
Pendulum Wave

When the motion of an object is influenced by gravity (eg free fall, pendulum, wave motion), that influence may provide a cue to computing the absolute distance and/or size of the object. Formal analysis supports the claim that the distance and size of moving objects are generally computable with reference to the gravitational component of motion. Informal evidence from judgments of realism in films is consistent with this gravity-cue hypothesis.

Quantitative Endoscopy: Initial Accuracy Measurements

2000 ◽  
Vol 109 (2) ◽  
pp. 128-132 ◽  
Author(s):  
Theodore O. Truitt ◽  
Roger A. Adelman ◽  
Dan H. Kelly ◽  
J. Paul Willging
Keyword(s):  
Object Size ◽  
Absolute Distance ◽  
Image Size ◽  
Absolute Size ◽  
Actual Object ◽  
Endoscopic Images ◽  
Endoscopic Image ◽  
The Mean ◽  
The Absolute ◽  
Size Estimates

The geometric optics of an endoscope can be used to determine the absolute size of an object in an endoscopic field without knowing the actual distance from the object. This study explores the accuracy of a technique that estimates absolute object size from endoscopic images. Quantitative endoscopy involves calibrating a rigid endoscope to produce size estimates from 2 images taken with a known traveled distance between the images. The heights of 12 samples, ranging in size from 0.78 to 11.80 mm, were estimated with this calibrated endoscope. Backup distances of 5 mm and 10 mm were used for comparison. The mean percent error for all estimated measurements when compared with the actual object sizes was 1.12%. The mean errors for 5-mm and 10-mm backup distances were 0.76% and 1.65%, respectively. The mean errors for objects <2 mm and ≥2 mm were 0.94% and 1.18%, respectively. Quantitative endoscopy estimates endoscopic image size to within 5% of the actual object size. This method remains promising for quantitatively evaluating object size from endoscopic images. It does not require knowledge of the absolute distance of the endoscope from the object, rather, only the distance traveled by the endoscope between images.

scholarly journals An independent distance estimate to the AGB star R Sculptoris

2018 ◽  
Vol 611 ◽  
pp. A102 ◽  
Author(s):  
M. Maercker ◽  
M. Brunner ◽  
M. Mecina ◽  
E. De Beck
Keyword(s):  
Scattered Light ◽  
Angular Size ◽  
Dust Particles ◽  
Phase Lag ◽  
Distance Estimate ◽  
Agb Stars ◽  
Absolute Distance ◽  
Absolute Size ◽  
Thermal Pulse ◽  
The Absolute

Context. Distance measurements to astronomical objects are essential for understanding their intrinsic properties. For asymptotic giant branch (AGB) stars it is particularly difficult to derive accurate distance estimates. Period-luminosity relationships rely on the correlation of different physical properties of the stars, while the angular sizes and variability of AGB stars make parallax measurements inherently inaccurate. For the carbon AGB star R Sculptoris, the uncertain distance significantly affects the interpretation of observations regarding the evolution of the stellar mass loss during and after the most recent thermal pulse. Aim. We aim to provide a new, independent measurement of the distance to R Sculptoris, reducing the absolute uncertainty of the distance estimate to this source. Methods. R Scl is a semi-regular pulsating star, surrounded by a thin shell of dust and gas created during a thermal pulse ≈2000 years ago. The stellar light is scattered by the dust particles in the shell at a radius of ≈19″. The variation in the stellar light affects the amount of dust-scattered light with the same period and amplitude ratio, but with a phase lag that depends on the absolute size of the shell. We measured this phase lag by observing the star R Scl and the dust-scattered stellar light from the shell at five epochs between June–December 2016. By observing in polarised light, we imaged the shell in the plane of the sky, removing any uncertainty due to geometrical effects. The phase lag gives the absolute size of the shell, and together with the angular size of the shell directly gives the absolute distance to R Sculptoris. Results. We measured a phase lag between the stellar variations and the variation in the shell of 40.0 ± 4.0 days. The angular size of the shell is measured to be 19.″1 ± 0.″7. Combined, this gives an absolute distance to R Sculptoris of 361 ± 44 pc. Conclusions. We independently determined the absolute distance to R Scl with an uncertainty of 12%. The estimated distance is consistent with previous estimates, but is one of the most accurate distances to the source to date. In the future, using the variations in polarised, dust-scattered stellar light, may offer an independent possibility to measure reliable distances to AGB stars.

Feature Analysers, Optical Illusions, and Figural Aftereffects

Perception ◽  
1977 ◽  
Vol 6 (4) ◽  
pp. 401-406 ◽  
Author(s):  
Tadasu Oyama
Keyword(s):  
Interaction Model ◽  
Size Ratio ◽  
Absolute Distance ◽  
Test Circle ◽  
Optical Illusions ◽  
Tuning Width ◽  
The Absolute ◽  
Delboeuf Illusion

Simple displacement models cannot explain some aspects of optical illusions and figural aftereffects. The orientation-detector interaction model proposed by Blakemore and others is more suitable to explain many aspects of the Zöllner illusion, positive and negative illusions, the effect of gap between the inducing and test lines, and the anisotropy of illusions. If we hypothesize size detectors whose tuning width and distribution steps are proportional to logarithmic size, interactions between them explain well the fact that the Delboeuf illusion and figural aftereffects of circles are determined by the size ratio of the inducing to test circle, not by the absolute distance between the contours of these circles.

scholarly journals Early and Late Changes in the Distal Forelimb Representation of the Supplementary Motor Area After Injury to Frontal Motor Areas in the Squirrel Monkey

2008 ◽  
Vol 100 (3) ◽  
pp. 1498-1512 ◽  
Author(s):  
Ines Eisner-Janowicz ◽  
Scott Barbay ◽  
Erica Hoover ◽  
Ann M. Stowe ◽  
Shawn B. Frost ◽  
...  
Keyword(s):  
Supplementary Motor Area ◽  
Temporal Dynamics ◽  
Squirrel Monkeys ◽  
Motor Area ◽  
Adaptive Plasticity ◽  
Behavioral Recovery ◽  
Retrieval Task ◽  
Absolute Size ◽  
The Absolute ◽  
Motor Areas

Neuroimaging studies in stroke survivors have suggested that adaptive plasticity occurs following stroke. However, the complex temporal dynamics of neural reorganization after injury make the interpretation of functional imaging studies equivocal. In the present study in adult squirrel monkeys, intracortical microstimulation (ICMS) techniques were used to monitor changes in representational maps of the distal forelimb in the supplementary motor area (SMA) after a unilateral ischemic infarct of primary motor (M1) and premotor distal forelimb representations (DFLs). In each animal, ICMS maps were derived at early (3 wk) and late (13 wk) postinfarct stages. Lesions resulted in severe deficits in motor abilities on a reach and retrieval task. Limited behavioral recovery occurred and plateaued at 3 wk postinfarct. At both early and late postinfarct stages, distal forelimb movements could still be evoked by ICMS in SMA at low current levels. However, the size of the SMA DFL changed after the infarct. In particular, wrist-forearm representations enlarged significantly between early and late stages, attaining a size substantially larger than the preinfarct area. At the late postinfarct stage, the expansion in the SMA DFL area was directly proportional to the absolute size of the lesion. The motor performance scores were positively correlated to the absolute size of the SMA DFL at the late postinfarct stage. Together, these data suggest that, at least in squirrel monkeys, descending output from M1 and dorsal and ventral premotor cortices is not necessary for SMA representations to be maintained and that SMA motor output maps undergo delayed increases in representational area after damage to other motor areas. Finally, the role of SMA in recovery of function after such lesions remains unclear because behavioral recovery appears to precede neurophysiological map changes.

scholarly journals Absolute distance interferometry for subaperture stitching of large freeform optics

2020 ◽  
Vol 238 ◽  
pp. 06011
Author(s):  
Jan Spichtinger ◽  
Michael Schulz ◽  
Gerd Ehret
Keyword(s):  
Measurement System ◽  
Optical Axis ◽  
Distance Measurement ◽  
Fizeau Interferometer ◽  
Absolute Distance ◽  
Local Surface ◽  
Surface Gradient ◽  
Freeform Optics ◽  
The Absolute ◽  
Subaperture Stitching

We are developing a form measurement system for the surfaces of freeform optics and large conventional optics. The specifications of the optics are diameters up to 1.5 m and radii of curvature down to 10 m. This includes optics like telescope mirror segments and synchrotron optics. Using a Fizeau interferometer, we propose a subaperture stitching method that involves vertically aligning the interferometer’s optical axis to the local surface gradient and measuring the absolute distance from the interferometer’s reference flat to the specimen. Experimental results for the absolute distance measurement are shown.

Trends in the population of the Northern Hairy-nosed Wombat Lasiorhinus krefftii in Epping Forest National Park, Central Queensland

1994 ◽  
Vol 1 (2) ◽  
pp. 141 ◽  
Author(s):  
Doug G. Crossman ◽  
Christopher N. Johnsow ◽  
Alan B. Horsup
Keyword(s):  
National Park ◽  
Absolute Size ◽  
Forest Region ◽  
Prolonged Drought ◽  
Males And Females ◽  
The Absolute ◽  
The Stability ◽  
Almost All

The Northern Hairy-nosed Wombat Lasiorhinus krefftii now survives only in Epping Forest National Park, central Queensland. The species was formerly more widespread in the Epping Forest region than at present. Its decline appears to have occurred in three distinct episodes of contraction, two of which were associated with prolonged drought. Indirect monitoring of abundance suggests that the population was stable from 1974 to 1981, when cattle were excluded from the Park, but has increased since 1983. A trapping programme between 1985 and 1989 suggests that the absolute size of the population may be about 70. The population contains approximately equal numbers of males and females; almost all females breed; and a large and apparently increasing proportion of the population consists of young animals. Further increases in density and range within Epping Forest National Park appear possible. Removal of some animals for translocation should be attempted when it is clear that such removals will not jeopardize the stability and vigour of the Epping Forest population.

Size and shape of eggs of Neognathae: effects of developmental mode and phylogeny

2017 ◽  
Vol 95 (5) ◽  
pp. 359-366 ◽  
Author(s):  
I.S. Mytiai ◽  
O.V. Shatkovska ◽  
M. Ghazali
Keyword(s):  
Absolute Size ◽  
Phylogenetic Relatedness ◽  
Developmental Mode ◽  
Size And Shape ◽  
Egg Shape ◽  
Lateral Zone ◽  
Shape Indices ◽  
The Absolute ◽  
Pointed End ◽  
Egg Diameter

We evaluated the variation in absolute size and shape of birds’ eggs and the effects of developmental mode and phylogenetic relatedness on these traits. Eggs were characterized by length, diameter, and three indices of egg shape. Indices of egg shape were calculated as the ratio of radii that described the curvature of pointed end (cloacal zone), blunt end (infundibular zone), and lateral zone to egg diameter. We found that eggs shape was less variable than the absolute size of eggs. Index of the cloacal zone was the most changeable and index of the infundibular zone was very conservative. Size and shape of eggs could be better explained with phylogenetic relatedness than developmental mode.

Fiddler Crabs Use the Visual Horizon to Distinguish Predators from Conspecifics: A Review of the Evidence

1997 ◽  
Vol 77 (1) ◽  
pp. 43-54 ◽  
Author(s):  
John Layne ◽  
Michael Land ◽  
Jochen Zeil
Keyword(s):  
Field Experiments ◽  
Angular Size ◽  
White Background ◽  
Fiddler Crabs ◽  
Absolute Size ◽  
Uca Pugilator ◽  
Glass Dish ◽  
Escape Responses ◽  
The Absolute

Male fiddler crabs, Uca pugilator (Crustacea: Decapoda), respond to conspecifics by claw waving, and to predators by freezing or escape. In field experiments it was found that this distinction was not made on the basis of angular size and speed, nor was shape important. The remaining possibilities were either the absolute size of the stimulus, determined from angular size and distance, or the position of the stimulus relative to the horizon. To distinguish between these, a crab was placed in a glass dish, and moved black stimuli on a white background, at a distance of 22 cm. Stimuli below the crab's horizon hardly ever evoked escape. However, identical stimuli partially or wholly above the crab's horizon produced escape responses whose frequency varied with the angular size of the stimulus. Halving the distance of the stimulus showed that it was angular and not absolute size that determines escape frequency; and experiments with a tilted horizon showed that it is the position of the stimulus relative to the eye equator that is important, rather than the geographical horizon itself. It has been concluded that crabs categorize stimuli as dangerous or otherwise by their position relative to the crabs’ visual horizon.

Expanding Angles? Systematic Distortions of Space Involving Angular Figures

Perception ◽  
1977 ◽  
Vol 6 (5) ◽  
pp. 571-582 ◽  
Author(s):  
Simon Heywood ◽  
Karen Chessell
Keyword(s):  
Absolute Distance ◽  
Per Se ◽  
The Absolute

Using simple, single angular figures, including figures containing only one line, we have shown systematic misestimations of distance defined by these figures. These misestimations are not related to the absolute distance per se, but are related both to the size of the angle defining the distance, and to the part of the angle defining it. Some implications of these findings are discussed.

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