An agent comprising: a sensing device configured to sense an object in a real space for a certain period of time; an existence probability map creation means configured to define the real space as a group of voxels, and record, based on the sensing, every predetermined time, a vote for a voxel of the group of voxels where the object was observed, and create an existence probability map on which information of an existence probability of the object is recorded for each of the voxels based on the recorded votes; an arrangeable position storage unit configured to store information of a plurality of arrangeable positions; characterised by: an evaluation value calculation unit configured to calculate an existence probability on a basis of the existence probability map, and to obtain an evaluation value for each arrangeable position of the plurality of arrangeable positions and for each of a plurality of imaging conditions at a predetermined time from an existence probability value of a voxel within a sensing area, the sensing area being defined by the respective arrangeable position and the respective imaging condition, the evaluation value being a value indicating at which position and under what imaging condition the agent can image the object in the best manner; and a control unit configured to select an arrangeable position of the plurality of arrangeable positions according to the evaluation value obtained by the evaluation value calculation unit for the respective arrangeable position, by selecting the arrangeable position from a combination of arrangeable position and imaging condition with the highest evaluation value, and to control a drive system for moving to the determined arrangeable position. a sensing device configured to sense an object in a real space for a certain period of time; an existence probability map creation means configured to define the real space as a group of voxels, and record, based on the sensing, every predetermined time, a vote for a voxel of the group of voxels where the object was observed, and create an existence probability map on which information of an existence probability of the object is recorded for each of the voxels based on the recorded votes; an arrangeable position storage unit configured to store information of a plurality of arrangeable positions; an evaluation value calculation unit configured to calculate an existence probability on a basis of the existence probability map, and to obtain an evaluation value for each arrangeable position of the plurality of arrangeable positions and for each of a plurality of imaging conditions at a predetermined time from an existence probability value of a voxel within a sensing area, the sensing area being defined by the respective arrangeable position and the respective imaging condition, the evaluation value being a value indicating at which position and under what imaging condition the agent can image the object in the best manner; and a control unit configured to select an arrangeable position of the plurality of arrangeable positions according to the evaluation value obtained by the evaluation value calculation unit for the respective arrangeable position, by selecting the arrangeable position from a combination of arrangeable position and imaging condition with the highest evaluation value, and to control a drive system for moving to the determined arrangeable position.