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Wednesday, March 11, 2020


When creating case reports, I like to use the terms from our discipline as defined in the various standards documents. Here are some of the most popular terms, and their definitions. Saving these here for quick reference.


The following definitions for terms used herein are taken from the SWGDE Digital & Multimedia Evidence Glossary, Version 3.0 (June 23, 2016):

  • Compression - The process of reducing the size of a data file. (See also, “Lossy Compression” and “Lossless Compression”.) 
  • Compression Ratio - The size of a data file before compression divided by the file size after compression.
  • Forensic Photogrammetry - The process of obtaining dimensional information regarding objects and people depicted in an image for legal applications. 
  • Image Analysis - The application of image science and domain expertise to examine and interpret the content of an image, the image itself, or both in legal matters. 
  • Image Comparison (Photographic Comparison) - The process of comparing images of questioned objects or persons to known objects or persons or images thereof, and making an assessment of the correspondence between features in these images for rendering an opinion regarding identification or elimination.
  • Image Content Analysis - The drawing of conclusions about an image. Targets for content analysis include, but are not limited to: the subjects/objects within an image; the conditions under which, or the process by which, the image was captured or created; the physical aspects of the scene (e.g., lighting or composition); and/or the provenance of the image.
  • Image Enhancement - Any process intended to improve the visual appearance of an image or specific features within an image. 
  • Multimedia Evidence - Analog or digital media, including, but not limited to, film, tape, magnetic and optical media, and/or the information contained therein.
  • Native File Format - The original form of a file. A file created with one application can often be read by others, but a file’s native format remains the format it was given by the application that created it. In most cases the specific attributes of a file (for example, fonts in a document) can only be changed when it is opened with the program that created it. [Newton’s Telecom Dictionary] 
  • Nominal Resolution - The numerical value of pixels per inch as opposed to the achievable resolution of the imaging device. In the case of flatbed scanners, it is based on the resolution setting in the software controlling the scanner. In the case of digital cameras, this refers to the number of pixels of the camera sensor divided by the corresponding vertical and horizontal dimension of the area photographed. 
  • Photogrammetry - The art, science, and technology of obtaining reliable information about physical objects and the environment through the processes of recording, measuring, and interpreting photographic images and patterns of electromagnetic radiant energy and other phenomena. [The Manual of Photogrammetry, 4th Edition, 1980, ASPRS] In forensic applications, Photogrammetry, sometimes called “mensuration,” most commonly is used to extract dimensional information from images, such as the height of subjects depicted in surveillance images and accident scene reconstruction. Other forensic photogrammetric applications include visibility and spectral analyses. When applied to video, this is sometimes referred to as “videogrammetry.” 
  • Pixel - Picture element, the smallest component of a picture that can be individually processed in an electronic imaging system [The Focal Encyclopedia of Photography, 4th Edition 2007].
  • Proprietary File Format - Any file format that is unique to a specific manufacturer or product.
  • Quantitative Image Analysis - The process used to extract measurable data from an image. 
  • Validation - The process of performing a set of experiments, which establishes the efficacy and reliability of a tool, technique or procedure or modification thereof. 
  • Video Analysis - The scientific examination, comparison, and/or evaluation of video in legal matters.
  • Video Enhancement - Any process intended to improve the visual appearance of video sequences or specific features within video sequences.

The following definitions for terms used herein are taken from the SWGDE Best Practices for Photographic Comparison for All Disciplines, Version 1.1 (July 18, 2017):

  • Class Characteristic – A feature of an object that is common to a group of objects.
  • Individualizing Characteristic – A feature of an object that contributes to differentiating that object from others of its class.

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