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current form, the CDB Specification does not mandate on synthetic environmental richness, quality and resolution.
Given the mandate of the CDB Specification to be platform independent, it cannot provide the implementation details of specific off-line database compilers or runtime publishers attached to
specific client-devices. Furthermore, since there is no standardization of the SE representation internal to client-devices they vary by type
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, by vendors, it is unlikely that such information would completely satisfy the interests of all developers. More importantly, the structure and
format of synthetic environment data ingested by each client-device is typically proprietary; as a result, it is impossible to fully describe the effort required to develop CDB off-line compilers
andor CDB runtime publishers.
1.3.3 What is a CDB
A CDB corresponds to a static synthetic representation of the whole earth; it is geographically divided of into geodetic tiles bound by latitudes and longitudes, each containing one or more
specific sets of features. It uses the WGS-84 earth model to provide geodetic interoperability. Each of the simulator client-devices accesses the CDB geospecific information using the WGS-
84 geodetic coordinate system.
A CDB contains the features and modeled representation of the synthetic environment. It contains terrain altimetry; its raster imagery, its attribution as well as 3D feature with their
modeled geometry, texture and attribution. The Specification also makes provision for the representation of moving models. The representation of moving models is comprehensive and
goes well beyond other visualization standards because it makes provisions for the standardized simulator naming conventions, material and feature attribution, radarlaser reflectivity, aircraft
and airport lighting systems, armaments, special effects, collision pointsvolumes just to name a few.
The Specification governs all aspects of the CDB, as follows: Data content and representation of the synthetic environment
Structure and organization of the synthetic environment File format of the synthetic environment as stored on media
The CDB Specification describes a modeled synthetic environment representation for distributed simulation applications. Section 1.6.5, Use of CDB in Applications Requiring Dynamic
Synthetic Environments discusses how a CDB-compliant simulator could be adapted to handle modifications of the synthetic environment in real-time.
Given the CDB’s structured representation and attribution of terrain, objects and entities, it is now possible to design a broad range of synthetic environment simulations that modify synthetic
environments in real-time. Such simulations can modify the CDB and notify their changes to the other simulation federate that share a CDB. This provides a synthetic environment that is
persistent and fully correlated across all simulation federates. For example, terrain trafficability
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It is precisely the intent of the CDB Specification to provide such standardization.
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could be handled by a new SE simulation that dynamically calculates soil moisture content as a function of localized rain precipitation and soil typescomposition. A second simulation would
then derive the resulting soil physics and determine vehicle wheel slippage across the varying terrain conditions.
The modificationnotification approach is well-suited for a broad gamut of SE simulations; however, some simulations are very data intensive and would require excessive broadcasting
bandwidths to other federates. In such cases, these dynamic simulations would have to be replicated in the other client-devices of the federation. Good examples of this are visual system
special effects e.g., rotor downwash effect, missile plumes, muzzle flashes, cast landing lights; typically such simulations are proprietary and intrinsic to the client-devices. Other examples of
this include the varying effects of weather
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local winds, temperature, humidity, particulates, etc. and oceans currents, temperature, etc..
1.4 Key Features and Characteristics of the CDB Specification
The following paragraphs provide an overview of key features and characteristics of the CDB Specification.
1.4.1 Synthetic environment Database for Simulation Applications
The CDB Specification is a simulator-level synthetic environment database Specification for use in real-time. The Specification is open, platform-independent and client-device independent.
The Specification defines all aspects of data representation and organization, and storage structure necessary to support full-mission real-time simulation. The CDB Specification
synthetic environment databases contain datasets that represent the features of a synthetic environment for the purposes of simulation applications. The CDB provides a time-invariant
synthetic environment representation of the earth, composed as terrain, naturalman-made features and moving models for use by SE authoring tools and simulators.
1.4.2 Logical Addressability
The CDB Specification provides for near-infinite addressability. The amount of information associated with a CDB is limited only by available disk storage. The CDB Specification allows
for a nearly infinite number of identifiers within a single CDB. Addressability is not expected to be a limiting factor even if we assume a yearly doubling of storage capacity.
1.4.3 High Spatial Resolution and Scalability
The CDB Specification provides for near-infinite resolution due its organization of data in LODs. The CDB Specification grid-organized data e.g., elevation, ground raster imagery,
ground properties is structured into an LOD hierarchy consisting of up to 34 LODs. Grid- organized data can be represented to a resolution of 13 microns.
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Time-varying weather simulation effects could be simulated by a “weather server” simulation subsystem which in turn can rely on the terrain elevation and terrain material datasets to perform its simulation of weather in
real-time.
