In aerial images

vertical line is of significant use for building extraction

which provides not only the key and reliable evidence for building existence

but also the height of buildings. In this paper

in order to extract vertical lines

a simple method for determining the vanishing point of vertical lines is first analyzed based on the knowledge about the aerial photogrammetry. It is demonstrated that

suppose the imaging plane in aerophotograph is approximately parallel with the horizontal plane

the central point of an aerial image is approximate to the vanishing point of vertical lines. This information provides a geometrical constraint for vertical line extraction in object space and makes the automatic extraction of vertical lines very straightforward and simple. Second

in order to improve the efficiency and precision of line detection and to acquire the complete description of vertical lines (e.g. line parameters

pixel positions

and length etc.)

the adaptive fuzzy Hough transform

which combines the geometrical constraint in object space and gradient orientation information in image space adequately to achieve an excellent performance

is adopted to extract vertical lines automatically. Lastly

the Experimental results are given to indicate that the presented algorithm is effective and efficient for real|time applications

and provides a key evidence and clue for automatic building extraction from aerial images.