Search results for "Time to contact"

Scale invariant line matching on the sphere

2013

International audience; This paper proposes a novel approach of line matching across images captured by different types of cameras, from perspective to omnidirectional ones. Based on the spherical mapping, this method utilizes spherical SIFT point features to boost line matching and searches line correspondences using an affine invariant measure of similarity. It permits to unify the commonest cameras and to process heterogeneous images with the least distortion of visual information.

Gradient-based time to contact on paracatadioptric camera

2013

International audience; The problem of time to contact or time to collision (TTC) estimation is largely discussed in perspective images. However, a few works have dealt with images of catadioptric sensors despite of their utility in robotics applications. The objective of this paper is to develop a novel model for estimating TTC with catadioptric images relative to a planar surface, and to demonstrate that TTC can be estimated only with derivative brightness and image coordinates. This model, called "gradient based time to contact", does not need high processing such as explicit estimation of optical flow and feature detection/or tracking. The proposed method allows to estimate TTC and give…

Effects of Adjacent Vehicles on Judgments of a Lead Car During Car Following.

2016

Objective: Two experiments were conducted to determine whether detection of the onset of a lead car’s deceleration and judgments of its time to contact (TTC) were affected by the presence of vehicles in lanes adjacent to the lead car. Background: In a previous study, TTC judgments of an approaching object by a stationary observer were influenced by an adjacent task-irrelevant approaching object. The implication is that vehicles in lanes adjacent to a lead car could influence a driver’s ability to detect the lead car’s deceleration and to make judgments of its TTC. Method: Displays simulated car-following scenes in which two vehicles in adjacent lanes were either present or absent. Participa…

The impact of rear-view mirror distance and curvature on judgements relevant to road safety

2011

We report two experiments that investigate the impact of rear-view mirror distance and curvature on distance, spacing, and time-to-contact (TTC) judgements. The variation in mirror distance had a significant effect on TTC judgements, but only marginally influenced distance and spacing estimations. As mirror distance increased, TTC was overestimated, which is potentially dangerous. Control conditions with identical visual angles across different mirror distances revealed that effects were not solely caused by variation in visual angle. The impact of mirror curvature moderated the effect. While observers were unable to compensate for the mirror distance effect, they could do so for the distor…

Allocentric time-to-contact and the devastating effect of perspective

2014

AbstractWith regard to impending object–object collisions, observers may use different sources of information to judge time to contact (tC). We introduced changes of the observer’s vantage point to test among three sets of hypotheses: (1) Observers may use a distance-divided-by-velocity algorithm or, alternatively, elaborated τ-formulae, all of which give exact tC information; (2) observers may use simple τ-formulae (i.e., formulae of the type: visual angle divided by its own first temporal derivative); (3) observers may capitalize on non-τ variables. Hypotheses (2) and (3) imply specific patterns of errors. We presented animated, impending collisions between a moving object and a stationar…

Effects of Task-Irrelevant Cars on Judgments of Deceleration and Time-to-Contact During Car-Following

2012

Rear-end collisions represent over 25% of crashes with other moving vehicles (NHTSA, 2005). Factors that potentially contribute to such accidents include a driver’s ability to respond to a lead car’s deceleration and to estimate how much time remains until a collision would occur (DeLucia & Tharanathan, 2009). Prior research (Oberfeld & Hecht, 2008) showed that time-to-contact (TTC) judgments of approaching objects were influenced by task-irrelevant distractor objects. This finding has implications for rear-end collisions when drivers must detect a lead car’s deceleration amidst surrounding cars. However, Oberfeld and Hecht simulated a stationary observer rather than a moving obser…

2014

Depressed patients frequently report a subjective slowing of the passage of time. However, experimental demonstrations of altered time perception in depressed patients are not conclusive. We added a timed action task (time-to-contact estimation, TTC) and compared this indirect time perception task to the more direct classical methods of verbal time estimation, time production, and time reproduction. In the TTC estimation task, the deviations of the estimates from the veridical values (relative errors) revealed no differences between depressed patients (n = 22) and healthy controls (n = 22). Neither did the relative errors of the TTC estimates differ between groups. There was a weak trend to…

The effect of body posture on long range time-to-contact estimation

2011

On Earth, gravity accelerates freely moving objects downward, whereas upward-moving objects are being decelerated. Do humans take internalised knowledge of gravity into account when estimating time-to-contact (TTC, the time remaining before the moving object reaches the observer)? To answer this question, we created a motion-prediction task in which participants saw the initial part of an object's trajectory moving on a collision course prior to an occlusion. Observers had to judge when the object would make contact with them. The visual scene was presented with a head-mounted display. Participants lay either supine (looking up) or prone (looking down), suggestive of the ball either rising…

Effects of distance and eye-height on time-to-contact estimates

2014

Les effets de la distance et du point-de-vue sur le jugement du temps de pre-contact Lors de la realisation d’estimations du temps de pre-contact (time-to-contact TTC), les observateurs utilisent parfois des informations erronees dans leurs jugements, privilegiant la rapidite de decision et d’action au detriment de la precision. Dans ce contexte, nous avons etudie le role de la position de l’observateur par rapport a l’approche du mobile. Cinq experiences ont testees les effets de la distance et de la hauteur des yeux de l’observateur. Le sol pouvait avoir une texture reguliere, irreguliere ou absente. En controlant le temps de visibilite, le TTC et la vitesse du mobile, nous avons evite de…