3D Image Metrology, traditionally called Photogrammetry, is a technique to measure three-dimensional coordinates using images and the principle of triangulation. By taking images from at least two different positions and measuring points of interest in each of the images, one can develop lines of sight from each location where in image was taken to the corresponding points on the object. The intersection of the lines of sight from each of the images for a particular point can then be triangulated, resulting in three-dimensional coordinates. The technology has been available for many years, but the time to develop film or glass plates before measurements could be performed hindered its widespread use. The advent of CCD-sensors and powerful computers have led to rapid developments in digital terrestrial mapping and digital close range applications.
Initial digital close-range photogrammetry (DCRP) development relied on manual measurements of each image and provided the capability for quick, accurate, and reliable in-place measurements of static or moving objects in vibrating or unstable environments (Atkinson K. B. 1996). The latest implementation techniques focus on the use of auto-processing targets to automate the measurement task for processing all the images as one task. This feature greatly improves the speed at which object coordinates can be measured and calculated. Today the high degree of automation, the very fast response, and very high accuracy of 3D Image Metrology systems lead to wider acceptance of the technology. They are viewed today as flexible and highly accurate coordinate machines.