Portable digital map reader

Claim 1

A portable appliance for displaying geographical data, in particular topographical or road maps, recorded on magnetic or optical media and organized on a plurality of levels, the appliance comprising a central processor unit associated with memories and I/O interfaces, said central processor unit selectively displaying objects constituting said geographical data in one of said plurality of levels depending on a desired display scale, means reading said magnetic or said optical media, at least one display screen for displaying said geographical data, and having a horizontal and a vertical axis, means for inputting control information to said central processor unit, and, electrical power supply means for powering said appliance, the appliance further including a compass for measuring the angle between the vertical axis of said display screen and magnetic north, and to send corresponding control information to said central unit based on said measured angle, said central unit responding to said corresponding control information by issuing a command to the display screen to cause the displayed image to be oriented as a function of said corresponding control information, wherein data symbols and legends are selectively imposed upon the associated displayed image in order to make said symbols and said legends readable.