To provide a method of specifying shadow areas in licensor output images, which can correctly specify a shadow area in a licensor output image.

When the ground is photographed by a licensor installed in a flight object 1 that flies in a determined height from the ground, information on sunlight irradiation direction is acquired according to acquisition timing of structure line data 2a of a licensor output image 2. Subsequently, a shadow area 4 is calculated in the structure line data 2a based on the information on sunlight irradiation direction when acquiring the structure line data 2a for every structure line data 2a and a 3-dimensional model 3 for an object to be photographed, and then the shadow area 4 is specified in the licensor output image 2.

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