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Synthetic Environment
Exercises
In a joint exercise of several simulators for example, training on various
weapon systems or vehicle systems involve a variety of different training
equipment and terrain databases. Flexibility is needed in order to configure
the training equipment according to each training requirement, varying from
single object training (gunnery training) to more complex exercises,
battlefield training. In DIS, resources are independent simulators controlled
by a simulation manager.
Resource management with a standard interface for a global resource
mechanism is required to enable the combination of single components to
be handled as one simulator. Resource State PDUs accompanied by Action
Request PDU and Action Response PDU enable the coupling of the
resources.
In cooperation with DIS, the DIS aggregate protocols, Aggregate Level
Simulation Protocols (ALSP), help in model interfaces through publish and
subscribe mechanisms. Emerged in a different organisation, Naval
Postgraduate School Network (NPSNET) is the first application to use IP
Multicast protocols which provide one-to-many and many-to-many delivery
services. However, IP Multicast uses the UDP protocols and therefore is an
unreliable connectionless service.
Reliable multicast protocols are not practical for large groups due to
inefficient bandwidth and the excess of guarantee messages.
As the military budgets were reduced in the late 1980s, it severely
affected the training cost, especially the travelling cost of gathering trainees
for training.
Before DIS, SIMNET was a pioneer standard for distributed interactive
simulations which did not require the use of specific hardware or lower
level protocols. SIMNET, the earlier, and DIS, the later, share the same
goals and purposes that enable training at a far lower cost than the real
operation. Initially, SIMNET focused on the network integration of
homogeneous training systems.
Interoperability is achieved when the training systems inter-operate to
present a single training exercise in the same space although the audience
are geographically dispersed. The synthetic environment, to the audience,
would be the same, exact environmental database. With the requirement of
the extension to heterogeneous training systems where different computer
systems from different contractors are employed to suit the legacy in
different locations, a new standard was needed. The heterogeneous
integration demands the change of run-time data interchange due to the
different environmental databases and the implementation of the data onto
different systems. The scenes of the synthetic environment in different
training systems did not look exactly the same due to different fidelity. The
Close Combat Tactical Trainer project was then designed in the early 1990s
to correct several problems in SIMNET, using the new Distributed
Interactive Simulation (DIS) protocol standard, IEEE standard 1279.
Synthetic Environment Database
A synthetic environment database is not a Relational Database
Management System (RDBMS) or a data repository supported by database
management capacity as Access or Oracle. It is much more complex. It
requires a set of integrated objects that define and describe a natural
environment. The data elements also concern the geographical region and
expected events as well as the encapsulation of the relationships amongst
data elements. The database must support multiple types of data and a wide
range of information, i.e. visual-based, sound, symbols, and radar. Other
data concerns the representation of the environmental objects and features,
i.e. terrain, atmospheric and oceanic features The representation of the
synthetic environment database includes cartographic, 3-D model instances,
terrain surfaces, textures, and topologic features.