Lukes - 2 
• Live simulation—real people operating with real equipment in the real world with appropriate simulation 
interfaces; 
• Virtual simulation—real people in simulators and simulations fighting in synthetic worlds; 
• Constructive simulation—aggregated wargames and analytical models operating in synthetic worlds. 
In the military context, “Everything short of combat is simulation” wherein advanced technology offers unique 
advantages to support complex operations, safely, economically, with enhanced opportunities for analysis and 
learning, and negligible environmental impact. 
To meet these technical challenges, the ADS Synthetic Environments Program seeks to create robust virtual 
worlds from operational terrain and environmental data sources of sufficient fidelity and currency to interact 
with the real world. These Synthetic Environments must realizable, affordable and supportable within disparate 
real-time simulators and simulations linked by local and long-haul networks. On-going efforts under the Synthetic 
Environments Program support new developments to incorporate weather, dynamic phenomena, dynamic terrain 
and objects within DIS. The program is now being expanded to address rapid construction of virtual worlds with 
research initiatives in digital mapping, softcopy workstations and cartographic image understanding. 
This objective of this paper is to highlight cartographic issues critical to Synthetic Environments and to 
identify some of the scene analysis and machine vision research issues central to this growing problem domain. A 
more general description of issues in the generation and use of synthetic environments in networked simulation 
can be found in Mamaghani. 3 
2 Cartographic Components of Synthetic Environments 
The cartographic components of the synthetic environment are largely familiar and not particularly unique 
or remarkable in themselves. The interesting aspect lies in the assessment of the available source data, efforts to 
enhance and augment this baseline data, how the components are assembled into an unified representation that is 
spatially coherent, and the generation of diverse run-time representations tailored to meet various needs within an 
ADS exercise. The generation of unified representations having spatial coherency at a level of detail and fidelity 
that balance suitable realism in distributed simulation with hardware constraints in computer image generation 
is the subject of ongoing research. 5 The primary cartographic components from which synthetic environments 
are constructed include the underlying ’bare earth’ terrain surface, man-made and natural features represented 
as two or three-dimensional boundaries or objects, and textures that can be used to convey natural patterns of 
vegetation, soils, water bodies, or synthetic man-made materials. 
2.1 Terrain Surface 
Generation of a synthetic environment typically starts with definition of the terrain surface geometry. Often, 
this is a gridded digital elevation model comprised by a matrix of elevation posts with spacing ranging from 
kilometers to meters depending on the application. Alternatively, Triangular Irregular Networks (TIN) provide the 
flexibility to construct a continuous surface of irregular triangles adaptively shaped to represent the terrain surface. 
Such gridded or TIN representations are used to characterize both the terrestrial landmass and underwater 
bathymetry. Attribution of surface material composition ranges from null to multiple values including soil type, 
land cover and/or land use. In many applications, terrain surfaces are characterized by a single elevation value 
at a given location; more advanced representations support driving ground vehicles over and under bridges or 
tunnels, conducting infantry operations within multi-story buildings or caves, and supporting naval operations 
on and under the ocean surface. These applications require the capability to represent multiple elevation values 
at a given location.