Project Developments with Broad Application The SEDRIS Project Team has developed several products that have broad application beyond those directly associated with SEDRIS Interchange Mechanism. The two principal products in this category are the environmental Data Coding Standard and the Spatial Reference Model. These products have been developed as essential components of SEDRIS in developing technology that promotes simulation interoperability.
Data Coding Standard
In order to support the unambiguous description of environmental data, SEDRIS specifies both a Data Representation Model (DRM) and a Data Coding Standard (DCS). The DRM addresses how to describe "environmental things" in data modeling constructs meaningful to simulation developers (e.g., geometry, feature, image, topology, and data table). It explicitly avoids enumerating all of the "environmental things" which these data modeling constructs could be used to represent. SEDRIS transmittals are expressed in terms of the DRM.
The DCS provides a mechanism to specify the environmental "things" which a data model construct is intended to represent. That is, a "tree" could be represented alternatively as a Point Feature, an Aggregate Geometry, a Data Table, a Model, or some combination of these and other data modeling constructs. Which of these the data provider of the SEDRIS transmittal chooses is orthogonal to what the "thing" is representing. The provision of such a "thing" in a SEDRIS transmittal pre-simulation must result in a shared understanding of "what the thing is and what it potentially means" to all participating applications.
The DCS explicitly addresses the environmental "enumeration problem" in an extensible manner capable of meeting the needs of both pre-simulation and runtime data interchange. It uses an approach compatible with major DoD initiatives in Data Dictionaries and Data Modeling for both the M&S and operational environmental communities which include:
- Joint Meteorology and Oceanography (METOC) Conceptual Data Model (JMCDM)
- U.S. Imagery and Geospatial System (USIGS) Conceptual Data Model (UCDM)
- M&S-specific Object Modeling Data Dictionary (OMDD) designed to support the Object Model Library (OML).
The DCS provides a rigorous, extensible, internally consistent, and increasingly complete data dictionary from which to select environmental objects and attributes for use in both simulation pre-runtime and runtime applications, as well as operational system use.
Spatial Reference Model
In order to support the unambiguous and lossless interchange of environmental data, SEDRIS specifies a Spatial Reference Model (SRM) which includes a set of inter-related spatial reference frames to which all environmental data is referenced. Unfortunately, no single spatial reference frame is capable of meeting the "position/orientation expression" requirements of all federations, nor necessarily even all simulations within a single federation, for numerous, valid modeling and engineering reasons. Spatial reference frames currently required by the M&S community are identified in the following table:
Although the SEDRIS requirement is focused on the pre-simulation phase of the federation life cycle, the large volume of environmental data typically required (coupled with the short timelines allowed for interchange) results in a tight performance constraint analogous to that at runtime. Accuracy constraints and the span of spatial reference frames encompassed are identical to those for runtime spatial referencing (whether for environmental or military models) as most simulations represent their local environmental data in the same spatial reference frame as that used by the military modelers (for performance reasons).
The SRM explicitly addresses the "spatial reference frame problem" in an extensible manner capable of meeting the needs of both pre-simulation and runtime data interchange. It uses an approach compatible with major DoD standardization activities in the C4ISR community and the Defense Information Infrastructure Common Operating Environment (DII COE). It consists of a:
- Well-organized and documented framework for spatial referencing that encompasses the primary spatial reference frames in use in the DoD today
Set of extremely accurate and efficient algorithms for inter-conversions which take into account the varying costs of transcendental functions on different processors Standard portable implementation of those algorithms with a simple-to-use Interface Specification.
Documentation for both these products is part of the SEDRIS Technical Documentation Set, and will soon be available from the SEDRIS Project at
www.sedris.org