Point-by-point analysis (also referred to as side-by-side comparison) is a subset of the forensic science of image analysis, although it is also widely utilized in many other disciplines. Essentially, it involves the photographic, or other image, comparison between two objects for the purposes of identification , or to draw conclusions about the contents of the image. Photogrammetry is sometimes used as a means of conducting a point-by-point analysis involving measurement, or measurement comparisons, of the object depicted in the image.
Side-by-side assessment with photographic, digital, or video images is used to make comparisons between aspects in images and known objects in order to proffer an expert opinion on either elimination or identification. Some common subjects of point-by-point analysis are facial comparisons made between identified suspects and images captured on surveillance video film (used at banks, retail and convenience stores, ATMs, etc.). Questioned images are often compared with those of a known camera in order to ascertain if the image was created by that specific camera. Cars, boats, planes, or other motor vehicles captured on surveillance or chase video are often compared with those impounded or recovered during the course of an investigation.
In the process of making the analysis, the image is examined in order to extract as much information from it as will be necessary in order to accurately compare the two objects (image and actual object). It is sometimes necessary to create an enhanced or otherwise improved version of the features within the image in order to optimally assess each point of comparison. An important aspect of point-by-point analysis involves the examination of content of the image. The process of content analysis involves arriving at conclusions based on the comparisons made, such as the exact contents of the image, the means or the process with which the image was created, the physical environment captured in the image (the lighting, composition, etc.), and the attributed origin (also called the provenance) of the image. Some examples of content analysis include patterned injury analysis, correlation of apparent injuries depicted in am image with autopsy or emergency medical records, adjudication of the type of camera used to create a particular image, and verification of a specific feature in an image, such as the registration or license plate number on a motor vehicle.
see also Art identification; Ear print analysis; Fingerprint; Identification; Photogrammetry.