Three-dimensional point group data indicating three-dimensional coordinate sets of three-dimensional points included in a common imaging space of one or more cameras is received, one or more images captured by the one or more cameras are transmitted, the one or more transmitted images are received, initial camera parameters of each cameras are decided based on one or more mounting locations and one or more directions of the cameras, corresponding points in the one or more images are calculated for each of the three-dimensional points, based on the three-dimensional point group data and the initial camera parameters, and one or more camera parameters of the one or more cameras are calculated based on pixel values at the corresponding points in the one or more images.