A device for deriving the contour lines for an object from stereophotographic films taken through photographic lenses comprises steroscopic viewing apparatus for comparing the films to locate the different points on the object having a selected height and for producing first position signals representing the positions of the different points in one of the films, and a correction mechanism responsive to the first position signals for producing second position signals which represent corrected positions of the points for defining a contour line corresponding to the selected height.
A method and apparatus for stereoscopic measurement of an actual value of depth in a subject through its three-dimensional image obtained from two stereoscopically photographed films by utilizing three factors, that is, the center of optical axis of an X-ray tube or a camera which is indexed from the films at the time of stereoscopic photography, distance of movement from the first photographic point to the second photographic point and distance from the X-ray tube or the lens to the film.
A method of detecting relief contours in digital images representing an aerial or satellite view of the ground includes the steps of calculating a digital elevation map from two stereoscopic images of the terrain, extracting crest lines in the digital map, projecting the crest lines into one of the stereoscopic images, calculating contours in the image and deciding that a contour is a relief contour if the distance to the closest projected crest line, in the sense of a particular affinity criterion, is below a particular threshold.
A coordinates measuring method in which the image information of the same point are derived as first, second and third information when viewed from at least three different directions, a first corresponding point is determined by deriving the correlation between the first and second information, and a second corresponding point is determined by deriving the correlation between the second and third information, and mismatching is decided when the first and second coordinates are not substantially coincident with each other.
