Figure 1: 60 NM video map of the airfield Neubrandenburg - Trollenhagen (ETNU)
The video mapper superimposes prominent points and lines such as the position of radio beacons, the course of airways or geographical contours into the PPI display. This information is displayed on a transparent film and scanned by a picture recording tube which runs synchronously with the tube in the PPI scope.
As the transparency (approximately 4x4 cm) is very small in relation to the screen size, the contours look very blurred when using a small scale. This is the reason why different slides with different scales are used, which then also have to be switched when switching the scale of the PPI-screen.
But more modern solutions access digital map material and display the desired information together with the digitalized target marks on a large-area daylight-capable plasma screen.
Figure 2: historical video mapper AN/GPA-131 with here only one of otherwise 3 to 4 converters