Bringing Aerial Mapping Down to Earth

Then, instead of the usual head-bobbing exercise associated with relating a scene with the inscriptions on a paper map, tomorrow’s flier could watch moving imagery of ground formations and installations on a cockpit display that changes even as the jet skims. above the terrain. At the same time, continuously updated flight information would be superimposed over the “moving picture” map.

The map could be displayed as a look-down plan view of topographic information that is colour-coded for quick comprehension. Or it could be presented in a three-dimensional, look-ahead perspective similar to the actual scene a low-flying pilot is witnessing at the moment. All are updated as swiftly as the human eye can perceive, always ignoring bad weather, and darkness or enemy jamming.

What makes such versatility possible is the magic of microelectronics, particularly the high-speed handling of digital data. The U. S. Defense Mapping Agency is translating conventional cartography into digital data encoded in bits that a computer understands to describe major natural and man-made features the world over. Digital data encompassing more than 250,000 square miles will be stored in the airborne electronic map’s computer memory.

Normally, such a vast expanse would require a computer memory with several billions of data bits, complicating the storage and retrieval functions. But if from this mass only relevant data could be retrieved, computer access would be hastened appreciably. To simplify and expedite the transformation of stored data into a displayed image, Hughes Aircraft Company specialists are employing sophisticated data compression techniques sort of an algorithmic shorthand to compact the stored data which later can be expanded and amplified when retrieved and converted to full-blown imagery. The process can be likened to squeezing a wet sponge; when released and soaked, it again regains its original volume.

With data compression, electronic map designers are able to distil information on 35 acres of landscape into only 64 stored bits, the equivalent of four words on the computer. In fact, 400 million data bits stored in the computer memory contain all the information necessary to describe a quarter-million square miles in great detail and with remarkably high resolution when displayed.

The map computer, constantly updated with navigational data, uses a predicted aircraft position to access and retrieve data from its memory even as the plane skims over the terrain. This new data is then expanded to display an imaged replica of the landscape as often as 20 times per second.

Such high-speed processing promises a versatility far beyond the outer limits of moving map displays, today’s most advanced aerial map systems. Moving map displays are filmstrips of sector maps projected on a cockpit display. However, the content of the film is fixed.

In contrast, an electronic map system would be much more flexible. It would be facile enough to alter a mission plan to meet suddenly changing conditions. It could display terrain information in a number of different modes, as illustrated. Ultimately, it could provide terrain information to other subsystems to enhance their functions. On low-level attacks, for instance, the electronic map could be integrated with terrain following/avoidance and weapon delivery systems to increase their reliability. The electronic map also could add new features to existing sensor systems. Or its data could incorporate anti-aircraft threat avoidance data. Besides such in-flight applications, the electronic map has the potential to aid in pre-flight briefings. With it, a pilot could preview his planned flight route via video before takeoff.

The Air Force’s Avionics Laboratory, the sponsor of the development, has explored more than 30 possible uses for the versatile aviation tool. And even though the system is still in experimental stages, pilots who have witnessed computer simulations of the Airborne Electronic Terrain Map System are enthusiastic about its future. Yet the proof of this pudding lies in the reading, beginning with pilot and engineering evaluation and human engineering studies after Hughes delivers the first working test model late next year- perhaps the preface to electronic cartography that may eventually free all fliers from needless paperwork.