A method for automatically extracting a working face area image of constructional
engineering comprises the steps of obtaining N building site photos to form a photo group, conducting aerial
triangulation analysis on the photo group to obtain
pose information of the photos, then reconstructing a scene three-dimensional model, and obtaining a projection matrix P<(i)> based on the
pose information of the photos and a
calibration matrix K<(i)> of the photos; according to the
point cloud and
project design information of the scene three-dimensional model, obtaining the positions of M working face areas, and obtaining a face domain
Omega<(j)> corresponding to the M working face areas; in the N photos, projecting the
Omega<(j)> through the projection matrix P<(i)> to obtain a projection area
omega (ij) on the ith photo, and finding out the projection
omega<(j)>max with the highest
Omega<(j)> resolution from the projection areas of the N photos, and converting
omega<(j)>max into a working face area orthographic image omega(-)<(j)>max by using the
homography matrix H<(ij)>C[Omega] of the image under the Omega<(j)> local coordinate
system derived fromomega<(j)>max by the invention. The extraction method can automatically extract a working face area image from a single photo with exact physical significance and
high fidelity.