1. Science of Crime Scenes
Chapter 7.3
Science of Crime Scenes

2. Photogrammetry and 3D Reconstruction
Science of Crime Scenes

3. 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

4. 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

5. 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

6. Science of Crime Scenes

7. 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

8. Science of Crime Scenes
Calibration of camera
Science of Crime Scenes

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

10. 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

11. Science of Crime Scenes
The scene
Science of Crime Scenes

12. Science of Crime Scenes
The measurements
Science of Crime Scenes

13. Science of Crime Scenes
The software
Science of Crime Scenes

14. Science of Crime Scenes
The rendering
Science of Crime Scenes

15. Science of Crime Scenes

16. 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

17. 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

18. Science of Crime Scenes

19. 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

20. 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

21. Science of Crime Scenes

22. Science of Crime Scenes

23. Science of Crime Scenes
Shipyard accidents
Science of Crime Scenes

24. Bloodstain pattern analysis (Luminol enhanced)
Science of Crime Scenes

25. Bloodstain pattern analysis
Science of Crime Scenes

26. Shooting reconstructions
Science of Crime Scenes

27. Height determinations
Science of Crime Scenes

28. Science of Crime Scenes
Object Comparison
Science of Crime Scenes

29. Science of Crime Scenes
Bombing Scenes
Science of Crime Scenes

30. Contaminated scenes (biological or nuclear)
Science of Crime Scenes