Digital Photogrammetry is the science of obtaining high-precision measurements from photographs and other forms of imagery. This ranges from aerial photographs for mapping, through close-range photos for medical measurements, to the use of digital images in sophisticated digital workstation. Digital photogrammetry is revolutionizing the way we think about and work with maps.

Photogrammetry has evolved from analog to analytical to digital (softcopy) photogrammetry. The main difference between digital photogrammetry and it's predecessors-analog and analytical-is that it deals with digital imagery directly rather than (analog) photographs. However, the mathematics of data processing models (e.g., orientation, triangulation, etc.) used in digital photogrammetry has been well established.

Photogrammetry has been used for a variety of applications, ranging from engineering design to natural resource and environmental inventory to hydrographic survey to archaeological mapping. Most topographic maps available today were created using photogrammetry, which is considered the primary approach to GIS base data collection and updating.

In digital photogrammetry, imagery of all types, including passive (e.g., optical sensing) or active (e.g., radar imaging), and taken from any platform (e.g., airborne, satellite, close-range, etc.) can be processed. Thanks to digital computing technology, the entire photogrammetric production process is digital, and many components have been automated.

In general, a photogrammetric project involves two stages: 1) acquisition of imagery and its support data (e.g., ground-control information) and 2) processing the imagery to derive image and vector products. The first stage involves several operation suchs as project design, mission planning, image acquisition, ground control and quality assurance. the second stage involves the use of a digital photogrammetric workstation (DPW) for processing.

The primary products of Digital Photogrammetry are digital elevation models (DEMs), ortho-rectified images (or ortho-images) and extracted features (vectors). The secondary products derived from primary products include contour maps (derived from DEMs), image contour maps (ortho-images with contour overlays), image line maps (ortho-images with vector overlays) and 3-D scene models (DEMs with draped images and 3-D features).