Abstract: In apparatus for displaying map information, at least two maps of the same terrain but of different scale from one another are provided on a movable platform so that a portion of one of the images can be selected and displayed through an optical lens projection system of fixed magnification onto a projection screen and displaying through the optical lens projection system a portion of the selected portion of the one of the map images on the projection screen to examine the display of the other map image in that detail permitted by the scale of the other of the map images at the fixed magnification.

Abstract: A projection device provided with at least two different enlarging projection systems for the projection on a screen of a set of at least two slides provided on one carrier, said slides covering the same area of a plan or map, one slide being more detailed than the other. The device projects the first less detailed slide entirely and the second or next, more detailed slide only in part but on a larger scale.The device comprises further a transparent runner indicating on the first slide the part of the next slide that is projected.