Basic Photogrammetry for Crime and Crash Scenes

Basic Photogrammetry for Crime and Crash Scenes

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Basic Photogrammetry for Crime and Crash Scenes
by George M. Bonnett, JD

Frustrated that the cost of photogrammetry software and the necessary training far exceeds the limits on your budget? One of IPTM’s latest articles, Basic Photogrammetry for Crime and Crash Scenes, written by George Bonnett, will show you the basics of two-dimensional photogrammetry.

Photogrammetry, or numerical rectification, is used to “map” various points on a single plane to the desired coordinate system. Numerical rectification is simpler than other techniques and the software required is usually much less expensive and easier to use. When dealing with crime or crash scenes, the desired coordinate system is usually a scale diagram and numerical rectification is ideally suited for this purpose.

You will see that while a two-dimensional plane is a prerequisite, this plane need not be a horizontal surface and there is no requirement that the entire photograph be of a single planar surface. In fact, the basic requirements for two-dimensional photogrammetry are a single photograph and a scale diagram of a two-dimensional surface within the photograph that contains the object that is the focus of the process. Numerical rectification requires that four control or calibration points be located on the plane that can be matched to four corresponding points on the scale diagram.

Mr. Bonnett takes you step-by-step through three different exercises that will teach you the basics of using photogrammetry to obtain measurements from photographic images using numerical rectification. Since the topics of creating a scale diagram and forensic mapping are outside the scope of this article, the author assumes you have previous experience in these areas.

George Bonnett is a combat proven Marine Corps aviator turned police officer turned attorney turned crash reconstructionist turned software developer and author (REC-TEC). His whole life has depended on minute attention to detail. In this book, he gives you the benefit of his years of experience.

Specifications: 38 pages; 8½”x11; saddle stitched; Publisher: IPTM (September 2005)

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