1. A coordinate-conversion-parameter determination apparatus comprising: an image capture circuit configured to generate a first image by photographing, at a first place, a marker that is placed in advance and whose position and shape are known and generate a second image by photographing, at a second place different from the first place, the marker; a memory; and one or more processors coupled to the memory, the one or more processors being configured to: detect feature points of the marker from each of the first image and the second image; calculate three-dimensional coordinates of each of the feature points of the marker in a camera coordinate system in which reference is the first place, based on a position of each feature point in the first image and a position of each feature point in the second image; calculate a coordinate conversion parameter so that a sum of absolute values of errors between three-dimensional coordinates in a world coordinate system, the three-dimensional coordinates in the world coordinate system being obtained by converting the three-dimensional coordinates of the feature points of the marker in the camera coordinate system by using the coordinate conversion parameter, and three-dimensional coordinates of feature points in the world coordinate system that correspond to the feature points of the marker in real space is minimized; convert the three-dimensional coordinates of each of the feature points of the marker in the camera coordinate system into the three-dimensional coordinates of the feature points in the world coordinate system using the calculated coordinate conversion parameter; and store, in the memory, the three-dimensional coordinates of the feature points in the world coordinate system in an initial map that is used to estimate at least one of a position and an orientation of the image capture circuit.