Science of Crime Scenes Chapter 7.3 Science of Crime Scenes

Photogrammetry and 3D Reconstruction Science of Crime Scenes

Photogrammetry and 3D Scanning The first crime scene maps based on pictures taken with calibrated cameras date back to the early 20th century. Both photogrammetry and 3D scanning yield 3D images of the crime scene software then produces reconstructions using 3D models with realistic textures. As with any new technology, the CSI must be mindful of the impact it may have in court, but also sure of the accuracy of the methods and the fit-for-purpose relevance of the devices Science of Crime Scenes

Science of Crime Scenes Photogrammetry Photogrammetry is a process for determining geometric properties and distances from two-dimensional (2D) photographic images. The simplest version is determining the distance between two points in a photograph, given the scale of the image which is why it is important to always provide a scale in images taken at crime scenes requires knowing the location of the camera in space, its orientation, and parameters It can be used for topographic mapping, surveying, collision engineering, and crime scene recording Science of Crime Scenes

Science of Crime Scenes Photogrammetry Points in 3D space are determined by measurements taken from two or more photographs taken from different common target points are chosen in each photograph Photogrammetry techniques rely on the collinearity equation to deduce object coordinates (3D) from various sensor planes (2D) at least six common target points are needed to solve the equations The camera location acts as the third point between common target points one and two, thus triangulating the points and deriving the location in 3D space Science of Crime Scenes

Science of Crime Scenes

Science of Crime Scenes Calibration Calibration of the camera is the first step of the process, using eight photographs of a reference picture. This stage assesses the lens distortions The crime scene examiner can then take various photographs of the scene, making sure there is enough overlap between any two successive photographs Science of Crime Scenes

Science of Crime Scenes Calibration of camera Science of Crime Scenes

Taking various photos of object, with overlap Science of Crime Scenes

Science of Crime Scenes Photogrammetry The photographs are then registered in the software and their overlapping points are marked in different views After integrating the distortion parameters using the first photographs, the set of photographs is scaled with one measurement The software then draws the map of the scene and takes measurements Finally, the results can be exported to animation software to create 3D animations Science of Crime Scenes

Science of Crime Scenes The scene Science of Crime Scenes

Science of Crime Scenes The measurements Science of Crime Scenes

Science of Crime Scenes The software Science of Crime Scenes

Science of Crime Scenes The rendering Science of Crime Scenes

Science of Crime Scenes

Science of Crime Scenes 3D Lasers Scanners a complimentary method to the traditional crime scene photographer, not a replacement it allows recording the entire crime scene, locating all potential pieces of evidence at once, at the very beginning of the investigation “Freezing” the images of the scene in this way establishes the crime scene—literally, the crime “seen” It not only secures the documented record of processing (what changes were made to the data), but also provides data for later analysis for auditing or reconstruction purposes Science of Crime Scenes

Science of Crime Scenes 3D Lasers Scanners A scanner exhaustively covers all three dimensions of the crime scene in a quick and detailed manner, collecting a huge quantity of data within a resolution of roughly 2–5 mm at 25 meters distance this precision is not the accuracy of the device, but its resolution the scan only records what is visible and does so via a normal photographic approach objects behind other obstacles or other objects will not be recorded The device scans everything in its line of sight by swiveling in 360 degrees, creating a several-million-point data set Science of Crime Scenes

Science of Crime Scenes

Science of Crime Scenes 3D Lasers Scanners To employ the scan for photogrammetry, overlapping scans are necessary the calibration and repositioning of the different scans are automatically made either through triangulation or using indicators Science of Crime Scenes

Larger scenes, longer range scans For middle- and longer-range scans, 3D scanners emit a beam of light (visible or not) and measure the distance of a point by the part of the beam reflected to the instrument The shape of the object is assessed by the time of flight of the incident and reflected beams; this technology allows very long range, up to 2 km Science of Crime Scenes

Science of Crime Scenes

Science of Crime Scenes

Science of Crime Scenes Shipyard accidents Science of Crime Scenes

Bloodstain pattern analysis (Luminol enhanced) Science of Crime Scenes

Bloodstain pattern analysis Science of Crime Scenes

Shooting reconstructions Science of Crime Scenes

Height determinations Science of Crime Scenes

Science of Crime Scenes Object Comparison Science of Crime Scenes

Science of Crime Scenes Bombing Scenes Science of Crime Scenes

Contaminated scenes (biological or nuclear) Science of Crime Scenes