What is the Synthetic Environment?

As used in SEDRIS, the synthetic environment is the representation of the natural environment at a specific geographical location including the external features of the systems within the simulated space. Therefore, the synthetic environment includes the terrain, terrain features (both natural and man-made), 3-D models of vehicles, personnel, and certain terrain features, the ocean (both on and below the surface), the ocean bottom including features (both natural and man-made) on the ocean floor, the atmosphere including environmental phenomena, and near space. In addition, the synthetic environment includes the specific attributes of the environmental data as well as their relationships.

What is representational polymorphism?

Representational polymorphism is the capability to provide multiple representational data sets for the same synthetic environmental object within a SEDRIS transmittal. For instance, a tree can be represented as a polygon structure in a visual scene with an image stamped on it, and as a point feature located at a specific point on the terrain with the attributes of trunk width, crown size, height, type of tree, etc. These two representations of a tree can be used in two different ways. The polygon representation is used by the image generator while the point feature with attributes is used by the computer generated forces modeling.

What is the difference between a data representational model and a data format?

A data representational model, or simply a data model, is a notation method for describing data. SEDRIS uses an object-oriented data model, which defines what the data classes are, what attributes are used to describe the data, and how the data classes relate to one another. As such, the data model provides a description that enables its users to understand what data is present and how it is organized.

A data format specifies the actual bytes used to store data on a storage medium. A specific implementation is defined for how the data objects are to be structured and identified on the medium. There are multiple ways of implementing a data format for a specific data model.

What is topology, why is it needed and who uses it?

Topology provides an explicit representation of the spatial relationships between objects (e.g., connectivity and adjacency). Topology provides the explicit representation of a spatial relationship instead of having to derive the spatial relationship by doing geometric calculations. A topology is a way of pre-computing the answers to spatial relationship questions.

From the standpoint of an image generator, where spatial relationships between environmental objects are not critical to creating a scene, topology is of little interest. But, from the standpoint of a computer generated force trying to determine if there is a road near the field "they" are in, a topological structure provides the identification of what environmental object is to their left, right, etc.

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Last updated: October 8, 1998