Photogrammetry represents a way of non-contact method of spatial documentation. Its general interpretation means a reconstruction of spatial dimensions from two- dimensional images. It is classified as an indirect method, as it determents spatial positions through series of recorded photographs. It is based on a principle similar to human eyesight – objects distance (i.e. point on an object) is obtained from relationship of two images of that object, which are moved apart by a certain value and a certain angle (like human eyes).The object is photographed through a series of shots that overlap each other. Series of overlapping photographs are then processed by a computer software. Software uses information about the camera (parameters like focal point, sensor size, position of sensors center, lens curvature) to define a system of equations, from which exact spatial coordinates are derived.
The development of computer-based photogrammetric algorithms has enabled incredible precision in 3D model reconstruction. Today, photogrammetry is used in many branches of science.
The accuracy of 3D models obtained from photogrammetry cannot be defined as in those obtained by laser scannng, as it depends exclusively on the size of the pixel that has been captured, i.e. the level of the sharpness of the image being used. The process of obtaining a 3D model requires a longer activation and processing time, but a higher- density and a much finer structure models are obtained than with a laser scan.