Thaindian News

London, Dec 2 (IANS) Two researchers have developed a method to help forensic experts lift data from crime scenes using just a single photograph.
“We have studied an unprecedented and original line of research in the field of criminology and forensic engineering, which makes it possible to derive metric data from a single image,” says Diego González-Aguilera, study co-author.

González-Aguilera is a researcher in cartography and soil engineering at the University of Salamanca in Spain.

The process starts by capturing an image that must include easily-identifiable details and at least three vanishing points (the convergence point of straight lines projected in one direction) as well as at least one distance in the scene.

These data are used to extract the structural components or most important objects in the image “automatically and robustly”.

As the structural features are geometrically related to the features of the scene and the camera itself, it is possible to take measurements and to analyse the dimensions of the scene based on distances, angles and surfaces.

This means that, at any time after having taken a photograph of a crime scene, forensic experts could establish that a knife was 32 cm away from the victim, or that there was an angle of 37 degrees between a trace of blood, a footstep and a bullet hole.

González-Aguilera says it is better to use a single image rather than several as it is often difficult to ensure that a range of photos overlaps well, and there are always parts of the scene or some features of it that cannot be correctly related to the rest.

This technique has been developed within the field of photogrammetry, a procedure to determine the geometrical properties of an object based on photographic images.

“Until now, this discipline required at least two images to be used in order to reconstruct a crime scene, but now we have broken that barrier”.

Another basic principle of photogrammetry and computational vision (another discipline also used in this study) is that it is impossible to reconstruct a 3-D crime scene based on a single image.

However, the new technology also overcomes this limitation, as it makes it possible to introduce known “restrictions” into the scene, such as the presence of parallel or perpendicular planes, enabling these to be represented in 3D, says a Salamanca release.

An IT tool written in VRML format (Virtual Reality Modelling Language) is used in order to visualise a crime scene from any viewpoint in an interactive and three-dimensional way. VRML is a “flexible, scalable and easy-to-use” language, designed specifically for this task.

These findings were published in the Journal of Forensic Sciences.