True ortho-image-assisted decision-making technology for urban planning and management

Geographical Information System (GIS) technology has been an important tool in supporting urban planning and management, bringing efficient accessibility to more, better and more timely information. Ortho-images, especially, urban true ortho-images are important in supporting decision-making in urban planning and management. This paper presents a methodology to automatically ortho-rectify large-scale urban aerial images for decision-making in urban planning and management. The methodology to generate true ortho-photos includes three steps: orthorectifying the displacement, detecting the occluded area, and refilling the occluded area. We first compute the coordinates of the input image pixels in the output ortho-image and the distance of the coordinates to the perspective centre. Meanwhile, we use a data matrix to store the coordinate and its distance. We then compare the coordinate with the existing coordinates in a matrix that holds the coordinates and distance. If two image pixels have the same coordinates in the output ortho-image, the one with the shorter distance representing the roof of the building is the true position of the pixel, and the other with longer distance is the bottom of the building. By creating an index image, the occluded area of the buildings can be recorded for next step in processing. Mosaics from neighbouring slave ortho-images can be used to refill the occluded areas in the master orthoimage. The experimental results of the ortho-image of downtown Denver, Colorado, demonstrated that our algorithms can effectively ortho-rectify dense urban building area, with the result that all buildings are placed in their TRUE positions, and all streets are visible.