1. A projection system comprising: a plurality of image projection apparatuses to together project one integrated image onto a projection face based on image information; a projection controller to divide the image information into a plurality of segment image data, and to instruct each one of the plurality of image projection apparatuses to project a corresponding one of the segment image data; a positional deviation detector disposed at each of the plurality of image projection apparatuses to detect a positional deviation at each of the plurality of image projection apparatuses; an identification unit to identify which image projection apparatus detects the positional deviation when the positional deviation detector detects the positional deviation to identify an image projection apparatus requiring a calibration processing; a projection unit to cause the identified image projection apparatus to project a calibration image information; an image capture apparatus to capture the calibration image information projected by the identified image projection apparatus onto the projection face; and a calibration unit to calibrate the segment image data projected by the identified image projection apparatus based on the calibration image information captured by the image capture apparatus.