In this article, photogrammetry expert, Steven Becker provides an introduction to some of the methods and techniques utilized by forensic experts in determining the make and model of vehicles captured in surveillance videos and other photo sources.
Confirming or Refuting Vehicle Make and Model in Videos and Images
When comparing images either from a photograph or still images of a video, there are important aspects to consider for vehicle identification. The shape of the headlights can be distorted if the lights are illuminated, or overexposed due to reflections. The lines of the vehicle may be distorted by panoramic lenses. The vehicle color may be altered by reflections, camera color enhancement, and the ambient lighting conditions (yellow or blue lights). Colors in video are digital and are represented by several factors that represent the color displayed. In physical color analysis, paint can be chemically analyzed to determine a match. Digitally we can analyze the following characteristics: Hue, Saturation, Luminescence, red, green, blue content proportions.
In the image below we have a vehicle of interest leaving the scene. Identification of possible vehicle models should start with all vehicles of a similar size. The vehicle approximate length and wheelbase are identifiable due to comparison of known dimensions in the photograph near the vehicle such as the width of parking lines. Physically measuring the scene and analyzing objects of known length and width in the video can aid in improving the accuracy of the measurement.
From there, distinguishing characteristics will narrow the make and model year of possible vehicles. Here we have a unique side reflector below a headlight that is recessed to near the front of the front left wheel well, taillights that wrap around to the upper portion of the side of the vehicle, and a sloping roof and windshield line.
The lack of lighting in front of the vehicle precludes identification of the grill and emblem, but excellent lighting from the side shows the wheel spoke pattern well, body color match door handles, and that it is a 4 door with a relatively short trunk lid. The similar vehicle in the lower left corner is one of a few models of vehicle consistent with the vehicle from the surveillance video. Digital color analysis provides that the vehicle color has: 107 hue, 60 saturation, 23 luminescence, 18 red, 30 green, 26 blue. The even proportion mix of colors and low luminescence indicate that this is a black car with a higher content of green and blue, but the lighting, shadows, and reflections must be taken into account. The best analysis would be to perform a color correction measurement by bringing a color chart to the scene and evaluating, then correcting for the chart’s digital color content.
The experts at Robson Forensic provide photogrammetric analysis of surveillance video, personal video, and still imagery. In addition to vehicle identification described in this article, we provide analyses for a wide range of purposes including:
- Speed measurements
- Measuring sizes and distances
- Time confirmation
- Color identification
- Suspect identification
- Authentication of videos and images
Mr. Becker is a degreed mechanical engineer with over 20 years engineering experience. He is an expert in Computer Aided Design (CAD) and photogrammetric analysis. He has been performing CAD and photogrammetric analysis since 1991 using numerous software packages, and continues to do so in his current work at Robson Forensic. His education and training in physics and engineering, as well as on the job training provided the basis for his understanding and application of photogrametry, which is determining distance and/or dimensions in photographs. He has testified in court related to the location, dimension, and distance measurements of evidence in photographs, videos, and has created 3D and 2D images of depictions of scenes. He has specifically testified about the content of objects and their dimensions in photographs which relate to physical measurements.