Human height estimation from highly distorted surveillance image

Video surveillance camera (VSC) is an important source of information during investigations especially if used as a tool for the extraction of verified and reliable forensic measurements. In this study, some aspects of human height extraction from VSC video frames are analyzed with the aim of identifying and mitigating error sources that can strongly affect the measurement. More specifically, those introduced by lens distortion are present in wide-field-of-view lens such as VSCs. A weak model, which is not able to properly describe and correct the lens distortion, could introduce systematic errors. This study focuses on the aspect of camera calibration to verify human height extraction by Amped FIVE software, which is adopted by the Forensic science laboratories of Carabinieri Force (RaCIS), Italy. A stable and reliable approach of camera calibration is needed since investigators have to deal with different cameras while inspecting the crime scene. The performance of the software in correcting distorted images is compared with a technique of single view self-calibration. Both approaches were applied to several frames acquired by a fish-eye camera and then measuring the height of five different people. Moreover, two actual cases, both characterized by common low-resolution and distorted images, were also analyzed. The height of four known persons was measured and used as reference value for validation. Results show no significant difference between the two calibration approaches working with fish-eye camera in test field, while evidence of differences was found in the measurement on the actual cases.     

基于3D激光扫描、多刚体重建和遗传算法优化的车-人碰撞事故再现模拟与损伤分析

目的利用3D激光扫描技术,结合多刚体动力学和遗传算法优化对一起汽车与自行车及其骑车人碰撞的交通事故进行再现模拟与损伤分析,为法医学死因鉴定提供生物力学依据。方法利用3D激光扫描技术对肇事汽车进行测量,根据测量数据建立人-自行车-汽车多刚体模型,并设置优化变量的取值范围,利用多目标遗传算法,带精英策略的快速非支配排序遗传算法求最优近似解,并与事故现场附近监控视频记录进行比较。结果事故车辆激光扫描重建结果良好,通过遗传算法优化收敛所获得的最优近似解中的假人、自行车、汽车的动力学行为与监控视频中所记录的三者动力学行为相符合,假人的损伤参数也与事故中骑车人的损伤情况及部位相一致。结论利用3D激光扫描技术,结合多刚体动力学和遗传算法优化可以对人-自行车-汽车碰撞前的运动状态、碰撞致伤过程进行重建,并对受害者的损伤进行力学分析,在交通事故受害人致伤方式鉴定及死因分析中具有应用价值。     

Efficient height measurement method of surveillance camera image

As surveillance cameras are increasingly installed, their films are often submitted as evidence of crime, but very scant detailed information such as features and clothes is obtained due to the limited camera performance. Height, however, is relatively not significantly influenced by the camera performance. This paper studied the height measurement method using images from a CCTV. The information on the height was obtained via photogrammetry, including the reference points in the photographed area and the calculation of the relationship between a 3D space and a 2D image through linear and nonlinear calibration. Using this correlation, this paper suggested the height measurement method, which projects a 3D virtual ruler onto the image. This method has been proven to offer more stable values within the range of data convergence than those of other existing methods.     

Suspect Height Estimation Using the Faro Focus3D Laser Scanner

At present, very little research has been devoted to investigating the ability of laser scanning technology to accurately measure height from surveillance video. The goal of this study was to test the accuracy of one particular laser scanner to estimate suspect height from video footage. The known heights of 10 individuals were measured using an anthropometer. The individuals were then recorded on video walking along a predetermined path in a simulated crime scene environment both with and without headwear. The difference between the known heights and the estimated heights obtained from the laser scanner software were compared using a one-way t-test. The height estimates obtained from the software were not significantly different from the known heights whether individuals were wearing headwear (p = 0.186) or not (p = 0.707). Thus, laser scanning is one technique that could potentially be used by investigators to determine suspect height from video footage.     

Simulation-based reconstruction of traffic incidents from moving vehicle mono-camera

Video recordings from digital cameras implemented in road vehicles present a valuable source of data concerning various dangerous traffic situations, i.e., road accidents or near-miss incidents. This data is readily available and numerous methods for forensic reconstruction of traffic situations from vehicle video were presented in the past. New alternative method for reconstruction of traffic situations from vehicle video is presented in this article. The method is based on the fusion of kinetic vehicle trajectory simulation within 3D laser scanner point cloud, projective geometry, and processing of video footage from moving vehicle camera. The method offers accurate reconstruction of general vehicle motion within relevant time domain whereby in-depth technical information about traffic incident can be quantitatively extracted from video footage. The result is physics-based 3D projection of simulated vehicle motion on the motion of real vehicle recorded by moving monocular camera. The method was validated within performed experimental test runs with respect to vehicle speed, distance travelled, acceleration/deceleration and directional quantities (yaw rate, yaw angle). The method was further applied in the reconstruction of real-world traffic events.     

Relative effects of posture and activity on human height estimation from surveillance footage

Height estimations based on security camera footage are often requested by law enforcement authorities. While valid and reliable techniques have been established to determine vertical distances from video frames, there is a discrepancy between a person's true static height and their height as measured when assuming different postures or when in motion (e.g., walking). The aim of the research presented in this report was to accurately record the height of subjects as they performed a variety of activities typically observed in security camera footage and compare results to height recorded using a standard height measuring device. Forty-six able bodied adults participated in this study and were recorded using a 3D motion analysis system while performing eight different tasks. Height measurements captured using the 3D motion analysis system were compared to static height measurements in order to determine relative differences. It is anticipated that results presented in this report can be used by forensic image analysis experts as a basis for correcting height estimations of people captured on surveillance footage.     

The applicability of holography in forensic identification: a fusion of the traditional optical technique and digital technique

In this study, the applicability of holography in the 3-dimensional recording of forensic objects such as skulls and mandibulae, and the accuracy of the reconstructed 3-D images, were examined. The virtual holographic image, which records the 3-dimensional data of the original object, is visually observed on the other side of the holographic plate, and reproduces the 3-dimensional shape of the object well. Another type of holographic image, the real image, is focused on a frosted glass screen, and cross-sectional images of the object can be observed. When measuring the distances between anatomical reference points using an image-processing software, the average deviations in the holographic images as compared to the actual objects were less than 0.1 mm. Therefore, holography could be useful as a 3-dimensional recording method of forensic objects. Two superimposition systems using holographic images were examined. In the 2D-3D system, the transparent virtual holographic image of an object is directly superimposed onto the digitized photograph of the same object on the LCD monitor. On the other hand, in the video system, the holographic image captured by the CCD camera is superimposed onto the digitized photographic image using a personal computer. We found that the discrepancy between the outlines of the superimposed holographic and photographic dental images using the video system was smaller than that using the 2D-3D system. Holography seemed to perform comparably to the computer graphic system; however, a fusion with the digital technique would expand the utility of holography in superimposition.     

The body-worn camera perspective bias

Objectives

Footage from body-worn cameras (BWCs) is sometimes used to assess the quality of police interventions. This study investigates whether there is a “body-worn camera perspective bias,” in which the point of view provided by the footage influences perception of an intervention.

Methods

Participants with different backgrounds (undergraduate students and police candidates) were randomly allocated to a group that looked at one of two videos showing a fictional police intervention during which lethal force was used against a subject; both videos showed exactly the same intervention, but one had been filmed with a BWC and the other with a surveillance camera installed in a top corner of the room. Participants were then asked to rate the appropriateness of the intervention.

Results

No camera perspective bias was found among university respondents. However a significant camera perspective bias was found among police candidates: respondents’ opinions on the appropriateness of the intervention were significantly different when the film was from the body-worn camera than when it was seen from the surveillance camera. This result may be explained by the finding that viewers of the BWC footage reported that the subject was further from the officer.

Conclusions

Results suggest that the more training individuals have in analyzing police interventions, the more affected they will be by the camera perspective in these interventions. One implication of these results is that the perspective of people assigned and trained to evaluate the appropriateness of an intervention (e.g., members of a committee monitoring police misconduct) might be biased if only video footage from a BWC is presented.

     

Obtaining confidence intervals and Likelihood Ratios for body height estimations in images

In forensic practice, height estimations on perpetrators visible in video footage from surveillance cameras are regularly requested. There are several ways to do this. Insight is gained into the difference between actual and measured heights by taking validation measurements of a number of test persons. Variation between actual and measured heights is decomposed into a systematic part (because of height loss by pose, 3D modeling of the scene of crime, operator biases) and a random part (due to natural variation). On this basis a method is described for obtaining confidence intervals for the height, including head- and footwear, of questioned persons in images. Since the number of test persons is usually limited, the result is in terms of the Student's t distribution. In addition, for cases in which a suspect is available, an expression is obtained for the Likelihood Ratio (LR), measuring the strength of evidence of resemblance of actual height of the suspect and measured height of the perpetrator. The Likelihood Ratio depends both on the rarity of the estimated perpetrator's height and its closeness to the suspect's height. Technical theorems included may be relevant for other forensic areas as well.     

基于视频的车速鉴定方法

视频监控设备的广泛应用为各类案件的侦破及取证提供了重要线索。利用高质量视频图像进行近景摄影测量、运动物体识别及跟踪的方法和技术已经较为成熟,但利用广角、低像素的视频监控录像定量描述车辆行驶速度的技术研究尚未开展。针对交通事故技术鉴定的实际需求,根据速度的一般计算方法和计算机视觉的基本原理,提出可以应用目前广泛使用的公共视频监控设备所拍摄的录像进行车辆速度计算的方法。     

Three-dimensional surface reconstruction for cartridge cases using photometric stereo

In forensic science, automated firearms identification is an important and yet unsolved problem. On the way to the solution, one of the most important phases is data acquisition. To be able to identify firearms in a reliable way, all the striated and impressed marks on metallic surfaces of cartridge cases should be visible. But two-dimensional images of cartridge cases are very sensitive to the type and direction of the light source(s). Depending on illumination conditions, the images of marks change drastically and sometimes they simply disappear. But, if the three-dimensional (3D) topography of the surface is obtained, the geometry of the marks, which is independent of the illumination, is available. Thus, by providing illumination independent features that can be used for automated matching, 3D data have the potential to make automated matching much reliable. In the literature on data acquisition for automated firearms identification, a few different ways of three-dimensional surface extraction are described, like laser interferometry or laser profilometry. This study presents a real life application of another method, photometric stereo, for the acquisition of 3D topographic data for cartridge cases, which is the one used in BALISTIKA Ballistics Image Analysis and Recognition System. In order to construct 3D topographic data, first of all, two-dimensional images were acquired using a specially designed set-up. After the images were calibrated radiometrically, photometric stereo method was applied. In order to minimize the low-frequency errors in the final surface, a surface-fitting algorithm was used. The method uses low-cost equipment and image acquisition is not time-consuming. Results were compared to interferometric measurement values for error assessment.     

Evaluation of anthropometric accuracy and reliability using different three-dimensional scanning systems

The aim of this study was to evaluate the accuracy and reliability of standard anthropometric linear measurements made with three different three-dimensional scanning systems namely laser surface scanning (Minolta Vivid 900), cone beam computed tomography (CBCT), 3D stereo-photogrammetry (Di3D system) and to compare them to physical linear measurements. The study sample consisted of seven cadaver heads. The reliability and accuracy were assessed by means of a series of 21 standardized, linear facial measurements derived from 15 landmarks taken both directly on the face with a set of digital callipers and indirectly from a three-dimensional (3D) soft tissue surface models derived from CBCT, laser surface scans and 3D photographs. Statistical analysis for the reliability was done by means of intraclass correlation coefficients (ICCs). Accuracy was determined by means of the absolute error (AE) and absolute percentage error (APE) by comparison of the 3D measurements to the physical anthropometrical measurements. All the 3D scanning systems were proved to be very reliable (ICC>0.923-0.999) when compared to the physical measurements (ICC; 0.964-0.999). Only one CBCT measurement (t-g) and one Di3D measurement (t-sn left) had a mean AE of more than 1.5mm. There are clear potential benefits of using 3D measurements appose to direct measurements in the assessment of facial deformities. Measurements recorded by the three 3D systems appeared to be both sufficiently accurate and reliable enough for research and clinical use.     

Comparison of the Performance of Two Methods for Height Estimation

Abstract: In the case study, two methods of performing body height measurements in images are compared based on projective geometry and 3D modeling of the crime scene. Accuracy and stability of height estimations are tested using reconstruction images of test persons of known height. Given unchanged camera settings, predictions of both methods are accurate. However, as the camera had been moved in the case, new vanishing points and camera matches had to be created for the reconstruction images. 3D modeling still yielded accurate and stable estimations. Projective geometry produced incorrect predictions for test persons and unstable intervals for questioned persons. The latter is probably caused by the straight lines in the field of view being hard to discern. With the quality of material presented, which is representative for our case practice, using vanishing points may thus yield unstable results. The results underline the importance of performing validation experiments in casework.     

2D/3D image (facial) comparison using camera matching

A problem in forensic facial comparison of images of perpetrators and suspects is that distances between fixed anatomical points in the face, which form a good starting point for objective, anthropometric comparison, vary strongly according to the position and orientation of the camera. In case of a cooperating suspect, a 3D image may be taken using e.g. a laser scanning device. By projecting the 3D image onto a 2D image with the suspect's head in the same pose as that of the perpetrator, using the same focal length and pixel aspect ratio, numerical comparison of (ratios of) distances between fixed points becomes feasible. An experiment was performed in which, starting from two 3D scans and one 2D image of two colleagues, male and female, and using seven fixed anatomical locations in the face, comparisons were made for the matching and non-matching case. Using this method, the non-matching pair cannot be distinguished from the matching pair of faces. Facial expression and resolution of images were all more or less optimal, and the results of the study are not encouraging for the use of anthropometric arguments in the identification process. More research needs to be done though on larger sets of facial comparisons.     

Variation in the Measurement of Cranial Volume and Surface Area Using 3D Laser Scanning Technology

Abstract: Three‐dimensional (3D) laser scanner models of human crania can be used for forensic facial reconstruction, and for obtaining craniometric data useful for estimating age, sex, and population affinity of unidentified human remains. However, the use of computer‐generated measurements in a casework setting requires the measurement precision to be known. Here, we assess the repeatability and precision of cranial volume and surface area measurements using 3D laser scanner models created by different operators using different protocols for collecting and processing data. We report intraobserver measurement errors of 0.2% and interobserver errors of 2% of the total area and volume values, suggesting that observer‐related errors do not pose major obstacles for sharing, combining, or comparing such measurements. Nevertheless, as no standardized procedure exists for area or volume measurements from 3D models, it is imperative to report the scanning and postscanning protocols employed when such measurements are conducted in a forensic setting.     

Application of 3D Laser Scanner to Forensic Engineering

In the case of building collapses and overturned structures, a three‐dimensional (3D) collapse or overturn model is required to reconstruct the accident. As construction sites become increasingly complex and large, 3D laser scanning is sometimes the best tool to accurately document and store the site conditions. This case report presents one case of a structure collapse and one case of an overturned crane reconstructed by a 3D laser scanner. In the case of structural collapse of a prefabricated shoring system, a 3D model reconstructed all the members successfully, a task that is nearly impossible using a scale such as a tape measure. The reconstructed prefabricated shoring system was verified through a structural analysis through comparison with the construction drawings to investigate faults in construction. In the case of the overturned crane, the jib angle and other major dimensions were successfully acquired through 3D laser scanning and used to estimate the working radius. As a result, the propriety of the working radius with the given lifting load was successfully determined.     

Virtual forensic anthropology: Novel applications of anthropometry and technology in a child death case

Full-body 3D virtual reconstructions were generated using 3D technology and anthropometry following the death of a young girl, allegedly from severe malnutrition as a result of abuse and neglect. Close range laser scanning, in conjunction with full colour digital texture photography, was used to document the child's condition shortly after death in order to demonstrate the number and pattern of injuries and to be able to demonstrate her condition forensically. Full-body digital reconstructions were undertaken to illustrate the extent of the malnutrition by comparing the processed post mortem scans with reconstructed images at normal weight for height and age. This is the first known instance of such an investigative tool.     

Sex Assessment from the Volume of the First Metatarsal Bone: A Comparison of Linear and Volume Measurements

Sexual dimorphism is a crucial characteristic of skeleton. In the last years, volumetric and surface 3D acquisition systems have enabled anthropologists to assess surfaces and volumes, whose potential still needs to be verified. This article aimed at assessing volume and linear parameters of the first metatarsal bone through 3D acquisition by laser scanning. Sixty‐eight skeletons underwent 3D scan through laser scanner: Seven linear measurements and volume from each bone were assessed. A cutoff value of 13,370 mm³ was found, with an accuracy of 80.8%. Linear measurements outperformed volume: metatarsal length and mediolateral width of base showed higher cross‐validated accuracies (respectively, 82.1% and 79.1%, raising at 83.6% when both of them were included). Further studies are needed to verify the real advantage for sex assessment provided by volume measurements.     

Moving Images Through an Assemblage: Police, Visual Information, and Resistance

Through interviews with police and document analysis this article examines the movement of video surveillance images from source to police to the courts in order to assess and refine the surveillant assemblage concept. Using this concept, the case study reveals asymmetrical criminalization processes involving movement of this visual information. The study finds that most video surveillance images transferred to police come from private sources as a consequence of function creep and that their movement epitomizes creation of criminalized ‘data-doubles’. However, the article argues that this criminalizing movement through the police is revealed as less than a seamless process; it is dependent on human labour and encounters forms of resistance along the way that include increased police workload and technological limitations.