Hierarchical, Three‐Dimensional Measurement System for Crime Scene Scanning

Abstract

We present a new generation of three-dimensional (3D) measuring systems, developed for the process of crime scene documentation. This measuring system facilitates the preparation of more insightful, complete, and objective documentation for crime scenes. Our system reflects the actual requirements for hierarchical documentation, and it consists of three independent 3D scanners: a laser scanner for overall measurements, a situational structured light scanner for more minute measurements, and a detailed structured light scanner for the most detailed parts of tscene. Each scanner has its own spatial resolution, of 2.0, 0.3, and 0.05 mm, respectively. The results of interviews we have conducted with technicians indicate that our developed 3D measuring system has significant potential to become a useful tool for forensic technicians. To ensure the maximum compatibility of our measuring system with the standards that regulate the documentation process, we have also performed a metrological validation and designated the maximum permissible length measurement error E for each structured light scanner. In this study, we present additional results regarding documentation processes conducted during crime scene inspections and a training session.

Temperature Compensation Method for Mechanical Base of 3D-Structured Light Scanners

“…In medicine, they have been used for spine curvature estimation [6,7], for gait analysis [8], for prosthetics [9,10], and for four-dimensional (4D) measurements of human bodies in motion [11][12][13]. In industry, they have been used to perform quality control [14][15][16], to support the Industry 4.0 intelligent systems [17,18], in augmented reality to support the documentation process of criminal events [19][20][21][22], and in archaeological sites or in cultural heritage conservation workshops as devices used for digitization for archiving or conducting analysis (e.g., analyzing the influence of conservation processes or for the analysis of ageing processes) [16,[23][24][25][26][27][28].…”

“…The variety of applications of 3D-structured light scanners is so extended as they can provide precise measurements of 3D geometries, often in a short time [4,[11][12][13]16,20,21,29]. A typical 3D-structured light scanner consists of 3 main units: a digital camera, a structured light projector, and a rigid mechanical frame which is a support for camera and projector [2,3,15,29,30] (see Figure 1).…”

“…The particular design can vary, depending on the size of the measuring volume and the required measurement uncertainty, speed of measurements, and number of detectors, as well as other factors including aesthetics and performance aspects. As the 3D scanning technique is a fully matured measurement technique, international standards ISO10360-8 [31] and recommendations VDI/VDE 2634 [32] have been proposed, which describe how the metrological validation process should be performed to calculate the maximum permissible error of a length measurement E MPE [15,20,[33][34][35]. Many factors affect the accuracy of a 3D-structured light scanner.…”

“…Some of these are listed in the Ishikawa diagram presented in Figure 2. In general, it is rather easy to indicate the potential sources of errors, but estimating the quantitative contribution of each factor to the overall measurement uncertainty and the final uncertainty of a particular 3D scanner is complicated [15,20,[34][35][36].…”

“…Among the factors presented in the Ishikawa diagram ( Figure 2), the effects of some on scanner uncertainty have not yet been entirely investigated; in particular, we are interested in temperature [15,20,34,37]. The effect of temperature on 3D-structured light scanners can be observed in three aspects: the effect on the digital camera, on the projector, and on the mechanical frame (often called the mechanical base) [2,3,30,38].…”