Aerial Photograph Reseau Mensuration with Sensing Arrays

A method is described for using a solid-state area array in a system to measure automatically the distance between reseau points on aerial photographs. An array is used to detect the center of reseau cross images by determining where the spatial derivative of the image goes to zero. Experimental results from actual aerial imagery show that it is possible to locate the center of typical reseau crosses to a repeatability of 2μm.