Photogrammetry is the science of obtaining accurate 3D measurements from multiple photos. “Photogram” is a photographic image made without a camera by placing objects directly onto the surface of a photo-sensitive material such as photographic paper and then exposing it to light. “Metry” refers to the science of measuring. Photogrammetry converts 2D dimensional photographs into the 3D dimensional realm using the fundamental principle of triangulation. Triangulation is the intersection of rays or line of sight in 3D space to accurately determine a location of a point. Thus, by having several photographs of the same object or scene from different camera angles, accurate details can be recreated in 3D.
There are two types of photographs used in Photogrammetry: terrestrial and aerial. Terrestrial photos are images taken from a ground based camera and are most commonly used in the vehicle accident reconstruction process. If an accident reconstructionist or engineer wants to find out how much deformation a vehicle has sustained, Photogrammetry can get the precise data the engineer needs to strengthen his or her analysis and opinion. Aerial photos are images taken from an aircraft or spacecraft, and are most commonly used for geology and topographic mapping. Both aerial and terrestrial photos are used in the field of forensics to gather critical information.
Using a series of high quality photos of an object from multiple angles, a “point cloud” can be generated by locating multiple common points in each of the photos taken. With enough points, or vertices created in X, Y and Z, a 3D spline cage or shape can be created. Photogrammetry is only as accurate as the photographs used; high resolution, clear photos will yield the most well-defined and accurate analysis.