Night-time surveillance system for forensic 3D mapping

This paper discusses a research in the development of a night-time surveillance imaging system for forensic mapping, and the exploitation of the system for crime suspect identification. The motivation of this research was to develop a precision stereo-imaging system using an off-the-shelf imaging sensor for 3D mapping of crime suspects. The prototype surveillance imaging system consisted of a high definition video (HDV) camcorder, a 3D stereo adapter, an Infrared (IR) filter and an IR illuminator. Using the concept of stereo-photogrammetry for craniofacial anthropometric measurement, body height and distinctive body feature of a suspect can be measured accurately in 3D. This study focused on the development and calibration of the prototype for surveillance purposes. A practical system evaluation was carried out at an ATM booth where stereo-video footage of a crime scene was captured and processed. The results of the research showed that the prototype was capable of obtaining spatial data with 27.0 mm accuracy in faint-light conditions and within 3.0 m from the imaging system.

I. Introduction

It is permissible to utilize video footage captured by surveillance imaging system as evidence in court. Several authors have discussed the use of single-image (2D surveillance) and multiple-images (3D surveillance) techniques for mapping crime suspects [10], [3], [14]. The mapping provides valuable information for the identification of crime suspects, and this information is acceptable in court. In general, mapping of crime suspects from footages taken in day light has few problems as long as the image resolution is adequate. However, similar image captured at night where lighting is inadequate can make the task very difficult as the footage is usually poor in contrast. Recent advances in stereo-imaging adaptor design, Infrared (IR) filter quality, and high-resolution camcorder produce high-quality IR stereo-images. The motivation of this research is to study the accuracy of mapping using these advanced technologies. Thus, the main objective of this paper is to discuss the development and calibration of the prototype 3D surveillance imaging system and the utilization of the system for forensic mapping. The discussion also includes a practical evaluation involving the mapping of crime scene at an ATM boot.