1. A display device, comprising: a detector for detecting a touch operation; an image acquirer for acquiring at least two of a navigation image containing map or nautical chart information created based on information obtained from a GNSS sensor for detecting a location of the display device, an underwater detection image created based on information obtained from an ultrasonic transducer for detecting underwater directly under the display device, and a radar image obtained from a radar antenna for detecting a location of an object around the display device; a display unit for displaying acquired images in respective divided areas of a display screen; a gesture detector for detecting a predetermined touch gesture based on the touch operation detected by the detector; an operated location detector for detecting an operated location of the touch gesture; a divided area identifier for identifying which image among the images is displayed in the divided area corresponding to the operated location detected by the operated location detector; and an image processor having a function to perform scrolling or zooming of the display screen corresponding to the touch gesture, and for changing a direction or a motion range according to the image being displayed in the identified divided area, upon performing the scrolling or zooming.