James S. Aber, ... Johannes B. Ries, in Small-Format Aerial Photography, 2010
Photogrammetry is the art, science, and technology of obtaining reliable information about physical objects and the environment through processes of recording, measuring, and interpreting photographic images and patterns of recorded radiant electromagnetic energy and other phenomena (Wolf and Dewitt, 2000; McGlone, 2004). Photogrammetry is nearly as old as photography itself. Since its development approximately 150 years ago, photogrammetry has moved from a purely analog, optical–mechanical technique to analytical methods based on computer-aided solution of mathematical algorithms and finally to digital or softcopy photogrammetry based on digital imagery and computer vision, which is devoid of any opto-mechanical hardware. Photogrammetry is primarily concerned with making precise measurements of three-dimensional objects and terrain features from two-dimensional photographs. Applications include the measuring of coordinates; the quantification of distances, heights, areas, and volumes; the preparation of topographic maps; and the generation of digital elevation models and orthophotographs.
Two general types of photogrammetry exist: aerial (with the camera in the air) and terrestrial (with the camera handheld or on a tripod). Terrestrial photogrammetry dealing with object distances up to ca. 200 m is also termed close-range photogrammetry. Small-format aerial photogrammetry in a way takes place between these two types, combining the aerial vantage point with close object distances and high image detail.
This book is not a photogrammetry textbook and can only scratch the surface of a continuously developing technology that comprises plentiful principles and techniques from quite simple to highly mathematical. In this chapter, an introduction to those concepts and techniques is given that are most likely to be of interest to the reader who plans to use small-format aerial photography, but has little or no previous knowledge of the subject. For a deeper understanding, the reader is referred to the technical literature on photogrammetry, for example, the textbooks by Wolf and Dewitt (2000), Kasser and Egels (2002), Konecny (2003), Luhmann (2003), Kraus (2004), McGlone (2004), Kraus et al., (2007), and Luhmann et al. (2007).
The basic principle behind all photogrammetric measurements is the geometrical–mathematical reconstruction of the paths of rays from the object to the sensor at the moment of exposure. The most fundamental element therefore is the knowledge of the geometric characteristics of a single photograph.