To provide a method and an apparatus for easily surveying a
road condition on the basis of photographed images photographed from the
sky even when there is an obstacle that partially covers a
road surface when viewed from the
sky.SOLUTION: An ortho-image creation method includes: a first photographing step of photographing a road, a
road surface of which is partially covered by an obstacle when viewed from the
sky, from an altitude higher than the obstacle to obtain a plurality of first photographed images; a second photographing step of photographing an area covered by the obstacle from an altitude lower than the obstacle to obtain a plurality of second photographed images; a first coordinate acquisition step of acquiring three-dimensional coordinates of a first feature point located outside the area covered by the obstacle and included in the plurality of first photographed images; a second coordinate acquisition step of acquiring three-dimensional coordinates of a second feature point located in the area covered by the obstacle and included in the plurality of second photographed images; and an ortho-image creation step of, on the basis of them, correcting the area covered by the obstacle on the
road surface to an area not covered by the obstacle.SELECTED DRAWING: Figure 5