Abstract: A hand-holdable viewer having a viewing end and a viewing axis, along the latter of which a transparent display is disposed. The viewer includes a Global Positioning System receiver (GPS) and a microprocessor connected to the GPS. The viewer is also provided with a slide holder for receiving a map slide having a map image and a EEPROM containing information about the geographical extent of the map image. When a map slide is inserted into the slide holder, it is aligned with the display, and so one is superimposed on the other, when viewed through the viewing end. The microprocessor reads the EEPROM and checks the GPS to determine whether the current position of the device is within the geographical extent of the map image. If this is so, the current position appears on the display. The EEPROM may also contain information about waypoints and routes which have previously been downloaded from a personal computer, or the like.