PURPOSE: To improve response characteristics by providing a display position correcting unit, by comparing a display position signal, obtained through the computation of a computing processor, to an azimuth signal right before display, and by correcting the difference.

CONSTITUTION: Computing processor 1 calculates a display position by a fetched azimuth signal and sends the result to display controller 3. Display correcting unit 4 fetches the azimuth signal from display unit 5 right after the completion of the calculation of computing processor 1, corrects a difference from the calculation result of computing processor 1, and feeds the corrected data back to display controller 3. As a result, display controller 3 displays the image of target video generator 2 on display unit 5 at a corrected display position.