Reverse Projection Photogrammetry

Nov 22nd, 2009 - Filed under: Blog,Image Analysis,Photography,Video Analysis

The Law Enforcement and Emergency Services Video Association (LEVA) held it’s annual conference this week. I was fortunate to attend the two day pre-conference workshop on reverse projection photogrammetry presented by Richard Vorder Bruegge, Walter Bruehs, and Chris Iber, all from the FBI Forensic Audio, Video, and Imaging Analysis Unit.

Reverse Projection Photogrammetry is used to measure objects in a photograph or video. It can be used to determine if an individual could be excluded or included as a suspect based on height. In addition to using this method to determine the height of an individual in an image, I have used this technique to determine the position of objects in relation to their surroundings (after the objects were removed), the distance of safety barriers in construction scenes (after the construction was completed and the barriers removed), the size of cracks in a sidewalk (after the sidewalk was repaired), etc. from photos of those scenes.

The workshop covered issues related to the methodology and foundations of this technique. Any forensic image analyst or forensic video analyst who hasn’t yet had the opportunity to take this workshop should do so. It has been offered at the LEVA conference for two or three years, and also at the IAI Annual Conference.


  1. Comment by Nicholas Guanti — December 15, 2009 @ 9:50 am

    I have been fortunate to have exchanged dialogue with both Mr. Bruegge and Mr. Bruehs regarding several areas of expertise and can support the benefit of understanding reverse projection by way of their highly technical knowledgebase. Mr. Bruegge also offers a wealth of knowledge in other areas of forensic image examination and analysis.

    Nicholas Guanti

  2. Comment by Robert Wyman — December 19, 2009 @ 4:50 pm

    George, I’m continuing to enjoy outstanding results with the iWitness photogrammetry program. I’m trying to employ it on every case, whether for actual documentation use or for my own continued training… and each case presents it’s own unique challenges!

    I’m going to “sanitize” some of the names and locations, then put a gallery of scaled CAD diagram files on my website, with each diagram derived from photogrammetry-based documentation. Recent cases include a freeway crash site that could not be measured with traditional tools, a pedestrian fall site in which a sidewalk was found to have a subtle … but significant… change in grade, and a vehicular damage case in which the impact angle became a critical element.

    I’m finding this “live” use of photogrammetry to be a unique tool in my crash-reconstruction arsenal.

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