Author/Editor		Zelasco, Jose F; Arcomano, Teresa; Dagum, Diego Amin; Donadio, Alejandra V; Donayo, Judith; Mendez, Daniel E; Pomerantz, Samuel
Title		Automatic obtaining of the digital elevation model by aerial photogrammetry
Type		članek
Source		Image Anal Stereol
Vol. and No.		Letnik 20, št. Suppl 1
Publication year		2001
Volume		str. 354-9
Language		eng
Abstract		When the pixels lines or image lines coincide with the epipolar lines of the stereo images, the automatic search of homologous points is simplified since it is made, essentially, traveling along image lines. The aerial images do not fulfil this condition, therefore a roto - rectification is required. With this operation, the image lines coincide with the epipolar lines. To achieve automatically the roto - rectification, a minimum number of 5 or 6 homologous points must be known. Their automatic search is not easy since the aerial image lines do not coincide with the epipolar ones. The search space can be narrowed, calculating in the second image of each pair of aerial images, the epipolar line corresponding to the point of the pair's first image. Moreover, with the pair of images previous to a given image in an aerial tail, one can obtain the object coordinates of some points located in the 20% area common to the stereo triple images. This reduces even more the search environment in the third image. 1f this information is not known, the search environment on the epipolar line may be diminished, estimating a ± delta h on and below the topographical surface, a value that is well-known when studying the project. With these elements, the approximate knowledge of the external orientation and other parameters, one can make the roto - rectification of the stereo images. And so, the digital elevation model may be obtained, applying the usual stereo matching algorithms.
Descriptors		PHOTOGRAMMETRY IMAGE PROCESSING, COMPUTER-ASSISTED