Photogrammetry is the science of
measuring two- or three-dimensional objects using only "photogrammes" (realistically, photogrammes is just a fancy word for
photographs, but in this day and age, the
images used for the measurements are just as likely to be
digital pictures or images from video or
CCD cameras or
scanners as they are to be actual photographs).
The principle advantage of measurements done through photogrammetry is that one can obtain highly accurate
results without actually touching the object being measured. This is very useful for creating
maps of particularly large objects or
terrains using
aerial photogrammetry, or for
architects or
civil engineers trying to
survey the status of
buildings, etc.