1. An image processing apparatus, comprising: a processor; and a memory storing instructions, which, when executed by the processor, perform a procedure, the procedure including: (a) acquiring image data representing successively captured images of a moving body's surroundings, and acquiring three dimensional position data representing three dimensional positions of a plurality of points on a solid object present in the moving body's surroundings as expressed in a moving body coordinate system set for the moving body; (b) calculating a movement amount that the moving body has moved during an interval from a first time to a second time; (c) identifying pixels representing a solid object in a first image captured at the first time based on the three dimensional position data acquired by (a); (d) creating, by virtual viewpoint projection, a first correspondence relationship indicating correspondence between each point on a three dimensional projection plane determined so as to contain the moving body therein at the first time and positions of each pixel of the first image, and, based on the movement amount calculated by (b), creating a second correspondence relationship indicating correspondence between each point on the three dimensional projection plane and positions of each pixel in a second image captured at the second time by expressing the position of the moving body at the second time in the moving body coordinate system at the first time, employing a virtual viewpoint projection that projects a captured image onto a virtual viewpoint projection plane that has a shape configured by a combination of a hemisphere of infinite radius with the position of the moving body as its origin, and a horizontal plane in which the moving body is present, and the virtual viewpoint projection re-projects points projected onto the virtual viewpoint projection plane onto the three dimensional projection plane with reference to a virtual viewpoint position; and (e) synthesizing a synthesized image by taking pixel values of pixels in a synthesized image corresponding to each point on the three dimensional projection plane as viewed from a specific viewpoint position, as pixel values of corresponding pixels of the first image based on the first correspondence relationship, and taking pixel values of each pixel in the synthesized image corresponding to pixels identified by (c) in the first image as being pixels representing a solid object, as pixel values of corresponding pixels of the second image based on the second correspondence relationship.