The DMA data base and its future enhancements have been hailed as the general solution to creating visual data bases for CIG. DMA centered approaches have proven marginal or ineffective, however, in providing visual support of low altitude flight, since DMA stresses navigation rather than flying skills.

The imagery presented by the CIG system must tell the pilot where he is relative to his map, and where he is relative to the ground. These are two very different objectives, and emphasizing one may compromise the other. Heavy emphasis on capture criteria' (for map fidelity) has historically resulted in systems which do an inadequate job of supporting low level flight, a task which depends on high â€˜scene density'. This paper examines the capture criteria and scene densities required to support such missions, and quantifies critical aspects of a â€˜nap of earth' data base. We will examine various constraints inherent in CIG systems, and their influence on what can be achieved. We also will discuss data base definition strategies, including the use of DMA data, to see where traditional approaches have been deficient in providing the required visual cues. Then we will present an approach which combines DMA data, new mathematical methodologies and data base design strategies, and current production hardware, to meet both the capture criteria and scene density needs of â€˜nap of earth' missions.

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Gary Wales