A graphics display terminal performs a pan operation with respect to a view motion center to effectuate spherical panning, thereby providing perspective and non-perspective views. Three dimensional instructions stored in terminal memory are re-transformed in accordance with a panned direction. Also a zoom feature is provided so that displayed images may be magnified as desired.

When drawing is being executed in an enlarged display that moves with the movement of a mouse, because the movement of the enlarged display area centers on the point of the whole image indicated by the moving mouse cursor, a difference arises between the amount of movement of the mouse cursor in relation to the whole image and the amount of movement of the mouse cursor in relation to the enlarged display image. An enlarged display movement method is disclosed that eliminates this difference. Enlarged display of an area centering on a point of a whole image indicated by a mouse cursor is displayed superposed over the original image and centered on the indicated point. As long as the mouse cursor is within the enlarged display area, drawing can be executed within the enlarged displayed area without the enlarged display area being moved, and when the mouse cursor moves outside the enlarged display area, a new enlarged display is executed centering on the present point indicated by the mouse cursor.

A display screen control method for a display device capable of supporting a logical screen larger in size than its physical screen is provided. This method enables a desired area to be displayed on the display device by a single operation. According to the method, a first rectangle similar to the logical screen is displayed on the physical screen, a second rectangle similar to the window area which was displayed within a view port in the physical screen is displayed in the first rectangle. The second rectangle is moved to a desired position within the first rectangle by a position indicating means such as a pointing device whereby the area the operator wishes to view is displayed in one quick operation.

Touch controlled zoom of a waveform display uses a touch screen for the display surface. Function buttons for moving or expanding the waveform display and for determining the axis of such movement or expansion operate in conjunction with a rotary encoder. Expansion, or zoom, is accomplished by contacting the screen overlying a point on the waveform about which zoom is desired. Such contact or activation of the expand function button results in movement of the rotary encoder providing a gain parameter to a zoom function. The zoom function operates on the waveform display in an exponential manner as a function of the gain parameter to expand or contract the waveform display about the zoom point according to the direction of rotation of the rotary encoder.

A map display apparatus for displaying a wide area map and an enlarged map is disclosed. When a display mode is shifted from the mode of displaying the enlarged map to the mode of displaying the wide area map, a cursor frame is displayed on a position on a parent screen corresponding to the divided area which has been displayed in an enlarged manner just before the shift of the display mode, so that the position on the parent screen of the area which has been displayed in the enlarged manner so far can be easily discriminated.