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A Comparison of Metrology Used in Documenting Shooting Incident Trajectories
Abstract and Figures
There are several methods and tools for documenting trajectory rods, but little research exists comparing accuracies of these methods. In this study, three targets were constructed, each having two sheets of 1/4 in (.635 cm) plywood separated by a 31/2 in (8.89 cm) void. Three shots from varying locations were taken at each of the targets for a total of nine shots. Prior to each shot, muzzle locations were documented with a total station, and afterwards the bullet hole locations were documented with the total station as well as a 3D laser scanner. Trajectory rods were then inserted through the primary and secondary bullet holes in the plywood targets and aligned using centering cones. This study compares the resulting accuracies from six different methods for documenting the trajectory rods. For each method, the resulting horizontal and vertical trajectory angles
were compared to the baseline LiDAR mapping of the bullet holes and muzzle locations. A total of 102 measurements were taken with a combined average horizontal angle accuracy of 1.2° and a standard deviation of 0.9°. The average vertical angle accuracy was 0.7° with a standard deviation of 0.5°.
Keywords: trajectory measurement, laser scanning, LiDAR, photogrammetry, photo scanning, reverse
camera projection, shooting reconstruction, crime scene reconstruction, forensic science
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... However, the accuracy of 3D laser scanning in a variety of forensic contexts has been widely reported and studied. Research using ground-truth known scenes and evidence has been conducted to validate the accuracy and integrity of the 3D data as well as forensic applications to bloodstain pattern analysis [15,16,17], ballistic trajectory determination and visualization [18,19,20], collision recording and reconstruction [21,22,23], clandestine grave documentation [24], and other crime scene reconstruction applications incorporating physical evidence [1,25,26,27]. ...
With increased improvements in digital imaging technology and their rapid uptake and use in everyday life, the general public are often recording day to day events as they happen. Law enforcement agencies have also increased the use of body-worn cameras to capture events. Combining 3D laser scan data of a scene with the image or video frame taken at the time of a crime or incident may provide information on the position and orientation of a camera at the time of recording, adding value to a police investigation by providing additional situational and spatial context. This project examined the accuracy of the Place In 3D function in FARO Scene to position an image or video frame from a non-fixed camera in 3D space at the time it was captured. Placement of the camera was accurate to approximately 22 mm, with similar levels of accuracy observed across all camera distances, locations, and camera types tested.
... Previously, this required personnel to navigate live worksites, climb onto stockpiles and manually map data points using GPS equipment. Continuous measurement of 3D surface roughness is necessary during the production process to guarantee that speci¯ed roughness tolerances are met (Jintao et al., 2010;Grant et al., 2019;Terpstra et al., 2020;Xhimitiku et al., 2021). Furthermore, the surface geometries must be checked. ...
3D scanning technologies are deployed toward developing a digital 3D model for Additive Manufacturing (AM) applications. It collects data, turning it into a 3D model that uses designated 3D printing processes. Many scanners, ranging from low-cost alternatives to professional series that are far more accurate and reliable, are now available to assist in bringing designs to reality. 3D scanning solutions enable the appropriate measurement of 3D physical parts into the virtual world, allowing factory production teams and corporate offices to share critical design information. These techniques are utilized everywhere in the design process, including product design and development, reverse engineering, quality control and quality assurance. The manufacturing sector can decrease costs while accelerating time to market and resolving quality issues. This study investigates the metrological need as per the advancements of 3D scanners. The procedural steps of the 3D scanners, along with specific metrological components and soft tools for 3D scanning, are discussed briefly. Finally, various 3D scanning applications are identified and discussed in detail. Because of the overall relative advantages of these non-contact measurement techniques, 3D metrological tools are crucial for modern production. Almost every sector aims for smaller, more complex components, which are more vulnerable to contamination or injury from even the slightest touch with a probe. The market is driven by global Research and Development (R&D) investment to develop game-changing technologies and solutions. Precision inspection and quality control are significant market drivers for industry progress. Smart factories will have lifetime access to 3D metrological data, allowing them to enhance quality and gain a competitive advantage in the marketplace.
... Previously, this required personnel to navigate live worksites, climb onto stockpiles and manually map data points using GPS equipment. Continuous measurement of 3D surface roughness is necessary during the production process to guarantee that speci¯ed roughness tolerances are met (Jintao et al., 2010;Grant et al., 2019;Terpstra et al., 2020;Xhimitiku et al., 2021). Furthermore, the surface geometries must be checked. ...
The revolutionary digital technology of drones, also known as unmanned aerial vehicles (UAVs), has altered healthcare. This technology proved highly effective for healthcare, research, start-ups, and large corporations. Various drones are used across the industries such as infrastructure, transportation, insurance, telecommunications, agriculture, media and entertainment, security, and mining. Drones have been utilized to help the medical industry for several years, with numerous start-up firms with considerable investment-testing innovative methods. This new drone delivery network will give healthcare practitioners and the communities they serve better access to critically needed therapeutic goods. Compared to traditional approaches, drones to map disaster zones give better cost savings and faster reaction times. Drones can immediately deploy, provide high-resolution and three-dimensional (3D) mapping, identify hotspot locations with the most damage, and upload data in real-time to coordinate rescue operations. This study is mainly about drones and their primary functions. Devoted features and various aspects associated with drone technology for healthcare are briefly discussed and, finally, significant applications of drones for healthcare are identified and discussed. The COVID-19 pandemic has brought to light several long-hidden health disparities worldwide. Drones have resulted in innovation, such as the unprecedented success of developing new vaccinations at record speed. Drones can distribute vaccinations in low-income countries, lowering transportation costs and increasing immunization rates. People are now receiving good care, and the medical infrastructure is also improving, which is made possible by drone technology.
Bullet trajectory documentation is an important part of shooting reconstructions. Manual methods are quite common, using a protractor and angle gauge, but more advanced methods using laser scanners and photogrammetry are also used for documentation. Past studies have shown that using terrestrial laser scanners (TLS) can reduce the variability in trajectory documentation. In 2020, Apple Inc. released the iPad Pro & iPhone 12 Pro with a Light Detection and Ranging (LiDAR) sensor, which effectively placed a low-cost laser scanner in mobile devices. In May of 2022, an iOS application focused on forensics called Recon-3D was released. Recon-3D uses Apple's LiDAR sensor and fuses it with photogrammetry to produce 3D point cloud data in the e57 format. The purpose of this research was to compare the accuracy, repeatability, and quality of 3D data, using Recon-3D to the Faro Focus S350 laser scanner in bullet trajectory documentation. As a first test, twelve trajectory rods were installed on a wooden panel in a controlled, indoor environment, in order to optimize the best settings for scanning trajectory rods. Subsequently, a more practical exercise was run outdoors with a vehicle containing five trajectory rods. The mean horizontal angle error for the twelve trajectory rods installed on the wooden panel was 0.14° with a standard deviation of 0.30°. The mean error for the vertical angle was - 0.05° with a standard deviation of 0.25°. For the outdoor vehicle test, the mean error for the horizontal angle was 0.03° with a standard deviation of 0.28°. The mean error for the vertical angle was 0.22° with a standard deviation of 0.36°. These errors are similar to other studies which utilize the terrestrial laser scanner with mean errors well below 1°. Although further work is required to make Recon-3D a more robust application, preliminary results are promising and in line with previous studies where the terrestrial laser scanner has been used. Thus, Recon-3D appears suitable to document trajectory rods when used in shooting reconstructions.
In 1980, research by Thebert introduced the use of photography equipment and transparencies for onsite reverse camera projection photogrammetry [1]. This method involved taking a film photograph through the development process and creating a reduced size transparency to insert into the cameras viewfinder. The photographer was then able to see both the image contained on the transparency, as well as the actual scene directly through the cameras viewfinder. By properly matching the physical orientation and positioning of the camera it was possible to visually align the image on the image on the transparency to the physical world as viewed through the camera. The result was a solution for where the original camera would have been located when the photograph was taken. With the original camera reverse-located, any evidence in the transparency that is no longer present at the site could then be replaced to match the evidences location in the transparency. Reverse camera projection is useful for both determining the location of historical evidence, where it is no longer physically in existence, as well as for directing the investigator to evidence still at the site that may otherwise have been overlooked during a site inspection. With the advent of augmented reality, an entirely digital process of this technique is now possible. This paper both presents a digital methodology and provides reference to a publicly available, augmented reality application developed specifically for this process by the authors. The accuracy of the application and methodology is then demonstrated through field studies with reported results.
Crime scene investigators are the foundation for every criminal investigation. The admissibility and persuasiveness of evidence in court, and in turn, the success of a case, is largely dependent upon the evidence being properly collected, recorded, and handled for future analysis by investigators and forensic analysts in the lab. Complete Crime Scene Investigation Handbook is the most complete, one-stop practical reference for law enforcement and crime scene professionals as well as students looking to enter the field. The book provides step-by-step methods and best practice protocols for effectively finding, recognizing, recording, collecting, preserving, handling, and packaging evidence. With more than 650 full color photos and illustrations the book covers: • The investigative team and its responsibilities • The rules for forensic search and seizure • Proper documentation of evidence via note-taking, photography, and sketching • Search patterns and the special considerations for various searches • The use of alternative light sources • Presumptive tests via luminol and other methods • Latent fingerprint processing • Evidence collection and packaging • Serological, trace, firearms, toolmark, footwear, tire, and digital evidence • Injury documentation • Appendices with a full compliment of sample forms, equipment lists, and checklists to assist in crime scene investigation A special considerations section reviews topics such as shooting scene and bloodstain documentation, clandestine graves and scattered human remains, fire scenes, and questioned document evidence. The final chapters examine how to develop a working plan and processing methodology as well as effective report writing. This book is a must-have reference for experienced forensic, crime scene, and investigative professionals as well as students in forensic science programs looking to enter the field. A specially developed companion lab exercise workbook-The Complete Crime Scene Investigation Workbook (ISBN: 978-1-4987-0142-6)-is also available for purchase and can be used in conjunction with this handbook, both for group training purposes or for individuals looking for hands-on self-study.
Professional American football games are recorded in digital video with multiple cameras, often at high resolution and high frame rates. The purpose of this study was to evaluate the accuracy of a videogrammetry technique to calculate translational and rotational helmet velocity before, during and after a helmet impact. In total, 10 football impacts were staged in a National Football League (NFL) stadium by propelling helmeted 50th percentile male crash test dummies into each other or the ground at speeds and orientations representative of concussive impacts for NFL players. The tests were recorded by experienced sports film crews to obtain video coverage and quality typically available for NFL games. A videogrammetry procedure was used to track the position and rotation of the helmet throughout the relevant time interval of the head impact. Compared with rigidly mounted retroreflective marker three dimensional (3-D) motion tracking that was concurrently collected in the experiments, videogrammetry accurately calculated changes in translational and rotational velocity of the helmet using high frame rate (two cameras at 240 Hz) video (7% and 15% error, respectively). Low frame rate (2 cameras at 60 Hz) video was adequate for calculating pre-impact translational velocity but not for calculating the translational or rotational velocity change of the helmet during impact.
The accident reconstruction community relies on photogrammetry for taking measurements from photographs. Camera matching, a close-range photogrammetry method, is a particularly useful tool for locating accident scene evidence after time has passed and the evidence is no longer physically visible. In this method, objects within the accident scene that have remained unchanged are used as a reference for locating evidence that is no longer physically available at the scene such as tire marks, gouge marks and vehicle points of rest. Roadway lines, edges of pavement, sidewalks, signs, posts, buildings, and other structures are recognizable scene features that if unchanged between the time of accident and time of analysis, are beneficial to the photogrammetric process. In instances where these scene features are limited or do not exist, achieving accurate photogrammetric solutions can be challenging. Off road incidents, snow covered roadways, rural areas, and unpaved roadways are examples where available scene features may be limited. Other factors like the number of photographs, the specific vantage of the photographs, and occlusion of recognizable features within these photographs can also limit the number of common features available for use in camera matching. In these instances, camera matching solutions can be improved by extending the 3D environment to include objects visible in the distance such as mountains, valleys, and other notable landmarks that are typically outside of the scope of 3D scene mapping. This paper demonstrates a method for obtaining and using this elevation data in combination with 3D scene mapping for camera matching photogrammetry. Photogrammetric solutions with limited scene features are compared to photogrammetric solutions based on the same limited scene features with the addition of digital elevation models. Solution accuracies from both scenarios are then individually evaluated to demonstrate improvements through use of elevation models. In this study, the incorporation of digital elevation modeling at a site with limited scene features, demonstrates a 74% improvement for evidence located through camera matching photogrammetry. For further evaluation, the camera match solutions were compared in combined solutions, where information obtained from one camera match was used to inform the next. This was done for both the scenario with digital elevation models and the scenario without. The results demonstrate how the number of available photos can influence the overall accuracy of photogrammetry solutions.
Three-dimensional (3D) technologies contribute greatly to bullet trajectory analysis and shooting reconstruction. There are few papers which address the errors associated with utilizing laser scanning for bullet trajectory documentation. This study examined the accuracy and precision of laser scanning for documenting trajectory rods in drywall for angles between 25° and 90°. The inherent error range of 0.02°-2.10° was noted while the overall error for laser scanning ranged between 0.04° and 1.98°. The inter- and intraobserver errors for trajectory rod placement and virtual trajectory marking showed that the range of variation for rod placement was between 0.1°-1° in drywall and 0.05°-0.5° in plywood. Virtual trajectory marking accuracy tests showed that 75% of data values were below 0.91° and 0.61° on azimuth and vertical angles, respectively. In conclusion, many contributing factors affect bullet trajectory analysis, and the use of 3D technologies can aid in reduction of errors associated with documentation.