Inter-camera Distance Research Articles

Improving pseudo-labeling with reliable inter-camera distance encouragement for unsupervised person re-identification

Improving pseudo-labeling with reliable inter-camera distance encouragement for unsupervised person re-identification

Image-Based Diagnostic System for the Measurement of Flame Properties and Radiation

Data collection in the field is fundamental in providing relevant information during fire spread across vegetation or in industrial environments. Considering the challenge and costs of obtaining measurements in the presence of a fire at such a large scale, the development of non-intrusive optical methods is a good alternative. As part of an ongoing effort to improve the understanding of wildfire spread and provide useful tools for fire management, an image-based diagnostic system is being developed for the three-dimensional reconstruction of the turbulent flame in the field. The method allows the time-resolved measurement of the geometric flame features (height, surface area and volume). This paper presents the application of two synchronized stereovision systems to static line of fire scenarios. Each stereovision system, with 1 m inter-camera distance, was located at 12 m from the fire and captured complementary images from front and rear views. Dual spectral band (visible-NIR) cameras were used to enhance fire pixel detection. A series of experiments were carried out on 5 m long and 2 m wide beds of excelsior in the open with fuel loads of 2, 4 and 8 kg/m2. The maximum flame heights were in the range of 1.2–2.4 m. Measurement of the heat flux densities was performed at several positions using thermopile-type sensors. Peak heat fluxes of 6.4–15.7 kW/m2 were measured at 3 m from the fire. The thermal radiation impinging ahead of the flame front was characterized according to its geometric properties. The results exhibit not only a linear relationship between the flame volume and radiant heat flux but also high correlations between their temporal fluctuations. The image processing technique enables measurements of flame volume to be a reliable substitute for the usual fire thermal properties.

Sampling design and analytical advances allow for simultaneous density estimation of seven sympatric carnivore species from camera trap data

Population density is a fundamental parameter needed to assess wildlife populations but is difficult to obtain given species are often wide-ranging and elusive. Photographic capture-recapture techniques do not require direct observations and thus, have become a common approach for estimating wildlife densities. To date, however, these studies have typically focused on single species. Our research explores study design- and analytical-based approaches for expanding photographic capture-recapture studies to assess multiple species simultaneously. We developed a hybrid-sampling scheme that varied inter-camera distances and used simulations to test the efficacy of this design versus a systematically spaced grid in estimating densities of species with varied space use. Through simulations we found the hybrid design facilitated density estimates for a wider range of species with little or no cost in accuracy for most species. We implemented a hybrid camera design across a 1154-km2 area in northern Botswana to estimate densities of lions, spotted hyenas, leopards, wild dogs, servals, civets, and aardwolves. We estimated densities of these small- to wide-ranging carnivores, where all or some portion of the population was individually identifiable, using spatially explicit capture-recapture and mark-resight models. Mean estimates ranged from 1.2 (95% CI = 0.72–1.99) lions to 10.1 (95% CI = 8.69–11.63) spotted hyenas/100 km2 and provided empirical information needed for the conservation of these species in Botswana. Our research demonstrates how photographic capture-recapture studies can be expanded to estimate the densities of multiple species versus just a single species within a community, thus increasing the conservation value of this globally implemented approach.

Adjusting stereoscopic parameters by evaluating the point of regard in a virtual environment

Despite the growth in research and development in the area of virtual reality over the past few years, virtual worlds do not yet convey a feeling of presence that matches reality. This is particularly due to the difference in visual perception of flat images as compared to actual 3D. We studied the impact of two parameters of the stereoscopic configuration, namely, the inter-camera distance (ICD) and the presence of a depth of field blur (DOF blur). We conducted an experiment involving 18 participants in order to evaluate this impact, based on both subjective and objective criteria. We examined six configurations which differed in the presence or absence of DOF blur and the value of the ICD: fixed and equal to the anatomical interpupillary distance, fixed and chosen by the participant, or variable, depending on the depth of the viewer’s point of regard (POR). The DOF blur and the variable ICD require the use of an eye tracking system in order to be adjusted with respect to the POR. To our knowledge, no previously published research has tested a gaze-contingent variable ICD along with dynamic DOF blur in a Cave Automatic Virtual Environment. Our results show that the anatomical and variable ICD performed similarly regarding each criterion of the experiment, both being more efficient than the fixed ICD. Besides, as with earlier similar attempts, the configurations with DOF blur obtained lower subjective evaluations. Although mainly not significant, the results obtained by the variable ICD and DOF blur are likely due to a noticeable delay in the parameters update. We also designed a new methodology to objectively compare the geometry and depth rendering, based on the reproduction of the same scene in the real and virtual setups, and then on the study of resulting ocular convergence and angular deviation from a target. This leads to a new comparative criterion for the perceptual realism of immersive virtual environments based on the visual behavior similarity between real and virtual setups.

The influence of viewing distance, depth range and inter-camera distance on depth perception and preference judgments in complex natural scenes

The influence of viewing distance, depth range and inter-camera distance on depth perception and preference judgments in complex natural scenes

New stereo shooting evaluation metric based on stereoscopic distortion and subjective perception

In this paper, we examined the stereoscopic distortion by varying image acquisition parameters including but not limited to inter-camera distance, camera focal length, and shooting distance. Since a lot of new elements or problems about stereoscopic perception have not been considered or precisely defined before, an advanced shooting principle is raised in this paper to guarantee the overall quality of stereoscopic images. In this paper, based on stereoscopic distortion and features of camera configurations, we present new shooting formulae for both toed-in and parallel camera configurations. Besides, a new shooting evaluation metric is proposed for the evaluation of stereo camera quality. The experimental results show that the proposed approach can precisely assess the visual perception quality of stereo images according to the shooting parameters and can effectively evaluate the quality of stereo camera.

Bayesian Early Mode Decision Technique for View Synthesis Prediction-Enhanced Multiview Video Coding

View synthesis prediction (VSP) is a coding mode that predicts video blocks from synthesised frames. It is particularly useful in a multi-camera setup with large inter-camera distances. Adding a VSP-based SKIP mode to a standard Multiview Video Coding (MVC) framework improves the rate-distortion (RD) performance but increases the time complexity of the encoder. This letter proposes an early mode decision technique for VSP SKIP-enhanced MVC. Our method uses the correlation between the RD costs of the VSP SKIP mode in neighbouring views and Bayesian decision theory to reduce the number of candidate coding modes for a given macroblock. Simulation results showed that our technique can save up to 36.20% of the encoding time without any significant loss in RD performance.

An algorithm to correct for camera vibrations in optical motion tracking systems

Recording and reconstruction of 3D motion capturing data relies on fixed, static camera positions with given inter-camera distances in a laboratory frame. To overcome this limitation, we present a correction algorithm that allows us to address camera movements in moving camera setups. Camera vibrations are identified by comparison of specialized target positions in dynamic measurements with their respective positions in static trials. This results in a 2D shift vector Δw⇒ with which the individual camera streams are corrected. The capabilities of this vibration reduction procedure are demonstrated in a test setup of four cameras that are (i) separately and (ii) simultaneously perturbed while capturing a static test object. In the former case, the correction algorithm is capable of reducing the reconstruction residuals to the order of the calibrations residual and enables reconstruction in the latter case, which is impossible without any correction. This approach extends the application of marker-based infrared motion tracking to moving and even accelerated camera setups.

수렴타입의 스테레오 영상 획득방법을 모사하는 변형평행타입에서의 주요인자의 정의

스테레오 카메라를 사용하여 입체영상을 획득하는 대표적인 방법으로는 수렴 및 평행방식이 있다. 본 연구는 수렴 및 평행타입의 장점을 갖추고 자연스런 입체영상을 획득할 수 있는 평행타입 기반의 변형평행타입 입체영상 획득 방법을 사용하여 수렴방식의 입체영상 획득방법을 모사할 수 있는 인자들의 추출 및 정량적 분석을 통하여 중요 핵심인자를 정의하였다. 결과적으로 변형평행 타입에서 수렴타입을 모사할 수 있는 인자들은 스테레오 카메라의 간격, 화각 및 수렴각이고, 융합영역 내에서의 핵심인자는 수렴각의 변화이다. 결론적으로 변형평행타입으로 수렴타입을 완벽히 모사할 수 있는 인자들의 정량적 범위는 사용환경에 따라 다르며, 초점길이가 짧을 수록, 수렴각이 작을수록 근거리 물체에 대한 수렴타입과 변형평행타입의 영상좌표의 오차량은 적다. The representative alignments for taking a stereo image by using a stereoscopic camera are the toed-in and the parallel alignment. In this paper, we tried to find important factors in the process that captures the stereo image by modifying parallel type 3D camera alignment to take the same object information as, for instance, when toed-in type was used. The modified parallel type 3D camera has merits in both types. As a result, three important factors are found by simulation to be inter-camera distance, field of view and convergence angle for both types. And the change of the convergence angle is known to be the most important factor at the stereo fusible area in processing. The effective ranges of these factors to simulate perfectly toed-in type by modified parallel type are strongly dependent on a user's circumstances such as mobile, official, theater and so on. Additionally, the error of the simulation is reduced when the focal length of the stereo camera is short and the convergence angle becomes smaller.

A study on the relationship between shooting conditions and cardboard effect of stereoscopic images

In this paper, we examine the cardboard effect by varying such image acquisition parameters as lighting intercamera distances, lens focal length, and presence or absence of motion parallax and backgrounds in program production. Subjective evaluation tests show that binocular disparity calculated from camera-separation lens selection and convergence point are dominant factors. The cardboard effect can be effectively avoided or lessened by enhancing increasing the binocular parallax. In case of actual program production, it is practical to use standard lenses or ones close in focal length to standard lenses, and to set camera separation around the same as the average eye separation of human eyes in order to mitigate the cardboard effect. When binocular disparity is small using lenses with long focal length, other cues, such as motion parallax accompanied by the relative movement between subjects and cameras, are effective.