photogrammetry

Photogrammetry is the science and technology of obtaining reliable information about physical objects and the environment through measurements made on photographs. It enables the reconstruction of objects and scenes in three dimensions from photographic images. Traditional photogrammetry used analog stereo imagery and instruments to measure coordinates, while modern photogrammetry relies on digital imagery and computer vision to extract 3D information. It encompasses metric photogrammetry, which aims for precise measurements, and close-range and aerial photogrammetry, which cover capturing small objects at close distances and landscapes or large structures from the air, respectively.

Typical workflows begin with image acquisition using calibrated cameras, often with overlapping views. In the orientation phase, software performs camera calibration and bundle adjustment to determine the relative positions and orientations of images. Dense reconstruction techniques, such as multi-view stereo, produce a dense point cloud or mesh. The data are then processed to create products such as orthophotos, digital elevation models, textured 3D models, or scalable point clouds.

Historically, photogrammetry emerged in the 19th century with stereo photography and mapping and advanced through aerial photography in the 20th century; the digital era popularized it through computer vision, structure-from-motion, and drone-based surveying. Modern work combines traditional photogrammetric principles with automated image matching and high-performance computing.

Applications span cartography, surveying, and civil engineering; archaeology and cultural heritage recording; film, gaming and virtual reality; architecture and construction; and industrial metrology and inspection. The field emphasizes accuracy, traceability, and repeatability, and outputs are governed by standards in geospatial data and metrology.