An information processing apparatus includes an input interface, a processor, and an output interface. The input interface obtains observation data obtained from an observation space. The processor detects a detection target included in the observation data. The processor maps coordinates of the detected detection target as coordinates of a detection target in a virtual space, tracks a position and a velocity of a material point indicating the detection target in the virtual space, and maps coordinates of the tracked material point in the virtual space as coordinates in a display space. The processor sequentially observes a size of the detection target in the display space and estimates a size of a detection target at a present time on a basis of observed values of a size of a detection target at the present time and estimated values of a size of a past detection target. The output interface outputs output information based on the coordinates of the material point mapped to the display space and the estimated size of the detection target.