
SEDRIS encompasses the environmental domain, which is described using its own unique definition of terms. To ensure a common understanding of terminology, definitions of these domain specific words and phrases are provided below.
2D+ topology  the addition of a z component to the traditional two dimensional (x and y) topology. 3D model  threedimensional, refers to the visual display that exhibits breadth, height, and thickness or depth. A abstract coordinate system (CS)  a means of identifying a set of positions in an abstract Euclidean space, comprised of a CS domain, a generating function, and a CS range. abstract object  conceptual objects including virtual, engineering, and/or mathematical models. accuracy domain (of S)  the set of valid coordinates in the coordinatespace of S that satisfy the accuracy domain template interval constraints evaluated with the SRFT parameter values for S. accuracy domain template (for an SRFT)  a set of coordinatecomponent value interval constraints expressed in terms of the SRF template parameters and a set of error bounds for positional, directional, and ratio errors. aggregating object  object that contains other objects (component objects). A 'hasa' relationship exists between the aggregating object and its component objects. For example, a polygon is an aggregating object for its vertex objects (components). Synonym: container. application program interface (API)  an encapsulation of functionalities common to many applications into reusable modules. This encapsulation provides consistency among applications, as well as a reduction in complexity for access of data. approximation error  The difference between the true value x and the approximation value x_{a}, caused by the replacement of theoretical formulations with approximations made to increase computational efficiency. areal feature  a geographic entity that encloses a region. For example, a lake, administrative area, or state. Aries true of date  the current first point of Aries. association  a relationship between two or more objects in a data representation model. This is the weakest relationship, and can include multiplicity of objects at either end of the relationship. atmospheric representation  the depiction of the atmosphere environment, which includes data on the location and characteristics of the zone from the Earth's surface to the upper boundary of the troposphere, and includes: (a) particulate and aerosol data on haze, dust and smoke (to include nuclear, biological and chemical effects), and (b) data on fog, clouds, precipitation, wind, condensation (humidity), obscurants, contaminants, radiated energy, temperature and illumination. attribute  one of the data types whose instances provide values that taken together specify the state of an environmental object. For example, the color of a building, or the width of a road. B base  1: the 'world' encompassed by an environment. Boundaries are specified to define the extent of the base. 2: the root of an environment object hierarchy of objects with fixed positions in the world. base quantity  one of a set of mutually independent quantities in terms of which other quantities can be defined and/or expressed as a product of powers of the base units and a real number [ISO 310: 1992]. base units  units for the base quantities in a coherent system of units [ISO 310: 1992]. basic Latin character  character from U+0020 to U+007E [ISO/IEC 10646]. basic Latin string  string consisting of Basic Latin characters. basic nonobject data types  single pieces of information such as numbers, codes, and other individual data items. binding constraint  a relationship in objectspace between the constructed entities of two or more bound RDs, or a size relationship between a reference datum primitive and its corresponding constructed entity. C celestiocentric SRFT  the generalization of geocentric spatial reference frames to include nonEarth objects. celestiodetic SRFT  the generalization of geodetic SRFs to include other planets and ellipsoidal bodies. celestiomagnetic SRFT  a spherical CS based SRFT aligned with the magnetic dipole of a celestial object. class  the term used to categorize the general form of object instances. (Each class definition specifies the methods (if any) that operate on the object.) classification  information defining the type of an object. code  compact and not necessarily humanunderstandable designator that is used to denote or identify a concept. coherent system of units  system of units chosen in such a way that equations between numerical values have exactly the same form (including the numerical values) as the corresponding equations between the quantities [ISO 310: 1992]. coherent unit  one of the units in a coherent system of units [ISO 310: 1992]. component object  object that is contained by an aggregating object. For example, vertex objects are component objects of their aggregating polygon. computational error  the combination of the digitization and approximation errors caused by the implementation of an approximation using a doubleprecision representation. (The magnitude of the approximation error usually dominates that of the digitization error and therefore the digitization error may generally be ignored.) computer generated forces (CGF)  a generic term used to refer to computer representations of forces in simulations that attempt to model human behavior sufficiently, so that the forces will take some actions automatically (without requiring manintheloop interaction). Also referred to as semiautomated forces (SAF). constraint  semantic condition or restriction [ISO/IEC 19501]. constructive simulation  models and simulations that involve simulated people operating simulated systems. Real people stimulate (make inputs to) such simulations, but are not involved in determining the outcomes. consumer  see resource consumers. container  see aggregating object. coordinate  an element of the CS domain of an abstract CS. coordinate system  an organized system for describing 2 or 3dimensional locations. coordinated universal time (UTC)  a temporal CS that is based on TAI by identifying every time second of TAI. correlated initial environment  the convergent representation of the same physical environment in two or more separate environments prior to their use in a combined exercise. correlated levels of detail (LOD)  the equal representation of environmental objects at comparable levels of presentation (i.e., the same object seen or detected at a distance of 15 meters). correlation  a convergent relationship between parallel representations of the same data. CS type  the coordinatespace and positionspace dimensions used to characterize an abstract CS. D data derivation  the calculation or interpolation of information not present in the original data. data dictionary  a table or set of records whose values define the allowable content and meaning of attributes. data loss  the loss of original information through multiple conversions or transformations of data. data model  description of the organization of, and relationships between, data in a manner that reflects the information structure. data predistribution interchange  the complete exchange of environmental data prior to the start of an exercise. data representation  a variety of forms used to describe the terrain surface itself, the features placed on the terrain, the dynamic objects with special 3D model attributes and characteristics, the atmospheric and oceanographic features, and many other forms of data. data representation model (DRM)  1: a description of the organization of data in a manner that reflects the information structure of an enterprise. 2: a description of the logical relationships between data elements. Each major data element with important or explicit relationships is captured to show its logical relationship to other data elements. deprecation  declaring a concept instance obsolete. derived units  units in a coherent system of units that can be expressed in terms of the base units by an algebraic expression [ISO 310:1992]. description  a precise statement of the nature, properties, scope, or essential qualities of a concept instance. designated spatial surface (DSS)  a surface in objectspace that may be used to represent an applicationspecific aspect of the objectspace. (Two important cases of DSSs are equipotential surfaces including geoids, and models of mean sea level surfaces based on sounding and tidal data.) digitization error  The difference between x and x_{c}, where x is a real number, and its representation on a digital computer is viewed as x_{c}. directed curve  a locus of points, if it is the range of a smooth curve. DRM constraints  usage rules for development of SEDRIS transmittals based upon the SEDRIS data representation model. dynamic temporal coordinate system  a Euclidean 1D CS based on data derived from the observation of a dynamic physical system, typically planetary motion. (The specification of a dynamic temporal coordinate system depends on the observed system being described by a mathematical model where time is one of the parameters that unambiguously identifies the configuration of the system. The time measurement can then be considered to be a measurement of position with units defined as a specified duration. Fixing an origin by specifying the initial conditions of the physical system and then continuously accumulating units of the duration specifies a dynamic temporal coordinate system.) E Earth gravitational model  spherical harmonic expansion of the gravitational field potential. (NOTE: Rotational effects are not included in this model; gravity includes rotational effects.) Earth reference model (ERM)  an ORM for which the spatial object is the Earth. ecliptic longitude (of the Sun)  the angle in radians from the first point of Aries and the line from the centre of the Earth to the centre of the Sun. ecliptic plane  plane defined by the orbit of a planet at a point in time. EDCS dictionary  set of entries of a similar nature each of which specifies a concept and includes a code, a label, and a concept definition as well as other conceptdependent information. edge  a onedimensional primitive used to represent the location of a linear feature and/or the border of faces. element  defined item within the abstract syntax.elevation  the vertical component in a 3dimensional measurement system. Elevation is measured in reference to a fixed datum. encoded transmittal  transmittal that has been encoded using a technique as defined in ISO/IEC 180232.enumerant  one of the possible values of an enumerated data type. enumerated data type  a data type whose values are specified from an ordered list of names. (The names are assigned numbers whose values indicate the position within the ordered list. It is these numbers that are actually manipulated by the implementation.) environment  set of physical circumstances and/or conditions, including both natural and manmade phenomena. environmental data  integrated set of data elements, each describing some aspect of an environment and the elements or events expected there. environmental domain  the physical or abstract space in which the entities and processes operate. The domain can be land, sea, air, space, undersea, a combination of any of the above (including permanent or semipermanent manmade features) or an abstract domain, such as an ndimensional mathematics space, or economic or psychological domains. environmental phenomena  an individual element of the physical environment (e.g., a rain system, fog, cloud). environmental representation  an authoritative representation of all or part of the natural environment, including permanent or semipermanent manmade features. epoch  the origin of an integrated temporal CS. equatorial inertial SRFT  a spherical CS based SRF aligned with the equator of a planet and the direction to the Sun at the vernal equinox (at a specified epoch). equatorial plane  plane through a designated centre of an object and normal to the rotational axis of the object. equidistant cylindrical SRFT  a equidistant cylindrical and augmented equidistant cylindrical map projection of the sphere RD component of the ORM. equinox  one of the two points of intersection between the orbit of a planet, and the line formed by the intersection of the ecliptic plane and the plane containing the Sun and parallel to the equatorial plane of the planet. equivalent units  set of units of measure that characterize the same physical quantity. F face  a region enclosed by an edge or set of edges. Faces are topologically linked to their surrounding edges, as well as to the other faces that surround them. Faces are always nonoverlapping, exhausting the area of a plane. fair fight  a simulation or exercise conducted such that differences in the simulator or training system technology do not unduly result in one force or entity having an advantage over another. feature  1: a model of a real world entity. 2: a static element of the environment that exists but does not actively participate in environmental interactions. fidelity  1: the accuracy of the representation when compared to the real world. 2: (a) the similarity, both physical and functional, between the simulation and that which it simulates, (b) a measure of the realism of a simulation, or (c) the degree to which the representation within a simulation is similar to a real world object, feature, or condition in a measurable or perceivable manner. first point of Aries (for the Earth)  the direction from the vernal equinox to the Sun. (The current first point of Aries is termed Aries true of date.) G geocentric SRFT  the generalization of geocentric spatial reference frames to include nonEarth objects, when the object is Earth. geocentric solar magnetospheric SRFT  a Euclidean 3D CS based planet centred SRF aligned with the direction to the Sun and the plane determined by that direction and the magnetic dipole of the planet, in the case of planet Earth. geodetic coordinate system (GDC)  a measurement system that relates Earthcentered angular latitude and longitude (and optionally height) to an actual point near or on the Earth’s surface. geodetic datum  datum describing the relationship of a coordinate system to the Earth [ISO 19111]. (NOTE: In most cases, the geodetic datum includes an ellipsoid definition.) geodetic SRFT  the generalization of geodetic SRFs to include other planets and ellipsoidal bodies, when the planet is Earth. geoid  a specific equipotential surface of the Earth’s gravity field that best fits the global mean sea surface in a minimum variance sense. (Global, regional, and local approximations of the geoid are developed from empirical measurements in association with specific ERMs.) geomagnetic SRFT  a spherical CS based SRFT aligned with the magnetic dipole of a celestial object, when the object is Earth. geometry  a very abstract class, encapsulating both the concepts of traditional geometry as well as other classes containing measured data, and organizational methods used to organize these traditional geometry and other 'real' data classes within an environment. Greenwich sidereal hour angle  the angle in radians from the first point of Aries to the direction of the xaxis of ORM WGS_1984 Earth reference ORM. (The Greenwich sidereal hour angle depends on the epoch of definition of the first point of Aries and is a function of UTC time t elapsed from a given epoch.) ground truth  the actual facts of a situation, without errors introduced by sensors or human perception and judgment. For example, the actual location, orientation, and engine and gun state of an M1A1 tank in a live simulation at a certain point in time is the ground truth that could be used to check the same quantities in a corresponding virtual simulation. Or the actual direct and diffuse solar irradiance at a terrain point is the ground truth that could be used to check the same quantity in a corresponding virtual simulation. group  one of the set of concepts that are members of an organizational schema. H heliospheric Aries ecliptic SRFT  a spherical CS based Sun centred SRF with zero spherical latitude aligned with the ecliptic plane and zero longitude aligned to the first point of Aries. heliospheric Earth ecliptic SRFT  a spherical CS based Sun centred SRF with zero spherical latitude aligned with the ecliptic plane and zero longitude aligned to the centre of the Earth. heliospheric Earth equatorial SRFT  a spherical CS based Sun centred SRF with zero spherical latitude aligned with the equator of the Sun and zero longitude aligned to the centre of the Earth. horizontal datum shift  a transformation between two celestiodetic SRFs for the spatial object Earth. I inertial direction  a direction with respect to the universe that is time invariant. inheritance  the objectoriented concept where a child class also has the features (attributes and methods) of its parent class. One of the types of relationships between objects in the data representation model. integrated temporal coordinate system  a Euclidean 1D CS based on a unit of duration that is derived from a physical phenomenon. (Fixing an origin (called the epoch) and then integrating continuously by accumulating units of the duration specifies an integrated temporal coordinate system.) intertransmittal referencing (ITR)  mechanism that allows relationship between objects contained in different transmittals.interchange  mutual interaction that effects an exchange of data or information. international atomic time (Temps atomique international, TAI)  the integrated temporal coordinate system with unit of duration of the SI second on the geoid and origin defined so that UT1TAI was 0 on 1 January 1958. (TAI is maintained by the Bureau International des Poids et Mesures (International Bureau of Weights and Measures, BIPM) and is generated by collecting and combining the data from a worldwide ensemble of atomic clocks.) International System of Units (SI)  coherent system of units, which includes seven base units together with derived units [ISO 310]. interoperability  1: enables distributed heterogeneous simulation systems to be interactive so that a meaningful exercise may be conducted. 2: the ability of a model or simulation to provide services to and accept services from other models and simulations, and to use the services so exchanged to enable them to operate effectively together. 3: two training systems interoperating to present a single training exercise in the same simulated space to a geographically dispersed audience. intervisibility  the translucency of superimposed visual objects (e.g., the ability to see through the leaves of a tree). ionosphere representation  see space representation. L label  a compact and humanunderstandable designator that is used to denote a concept. Lambert conformal conic SRFT  a Lambert conformal conic and augmented Lambert conformal conic map projection of the oblate or sphere RD component of the ORM. level of detail (LOD)  alternate representations of an object at varying fidelities based on some criteria. levels of topology  level 0 topology manipulates the purely geometric aspects of the spatial data. No topological information is stored in level 0 topology. Level 1 topology maintains a nonplanar graph. Level 2 topology maintains a planar graph. Level 3 topology explicitly represents the faces defined by the planar graph.library  a complete list of unique item(s) of a certain type (whatever type the library contains) that can be referenced within the environment. linear network  a geographic entity that defines a linear (onedimensional) structure. For example, a river, a road or a state boundary. link association  a class containing the attributes of an association (link) between two other classes. The link association is depicted using the ‘horsecollar’ symbol. The attributes in a link association class are properties of the association, not the classes linked by the association. littoral region  1: defined as (a) seaward  the area from the open oceans to the shore that must be controlled to support operations ashore, and (b) landward  the area inland from the shore that can be supported and defended directly from the sea. 2: the area from the tenfathom curve shoreward to the most inland point of the shoreline. live simulation  a simulation involving real people operating real systems. local space azimuthal 2D SRFT  an azimuthal CS based SRF for 2D abstract space. local space polar 2D SRFT  a polar CS based SRF for 2D abstract space. local space rectangular 2D SRFT  a 2D Euclidean spatial reference frame for an abstract 2D space. local space rectangular 3D SRFT  a 3D Euclidean spatial reference frame for an abstract 3D space. local tangent space azimuthal spherical SRFT  azimuthal spherical spatial CS with the zero 3^{rd} coordinatecomponent surface that is tangent to the oblate ellipsoid RD and with CS natural origin at the tangent point. local tangent space cylindrical SRFT  cylindrical spatial CS with 3^{rd} coordinatecomponent surfaces that are parallel to a tangent plane to the oblate ellipsoid RD. local tangent space Euclidean SRFT  Euclidean 3D spatial CS with 3^{rd} coordinatecomponent surfaces parallel to a plane tangent to the oblate ellipsoid RD. location 3D vertex  a coordinate in 3dimensional space. lococentric Euclidean 3D SRFT  Euclidean 3D spatial CS with a localised origin and axes orientations. lossless  not losing any data, information, or quality. M manintheloop (MIL)  a model that requires human participation. Mercator SRFT  a Mercator and augmented Mercator map projection of the oblate or sphere RD component of the ORM. metadata  1: data about data [ISO 19115]. 2: information describing the characteristics of data. 3: descriptive information about an organization’s data, data activities, systems and holdings. MIP level  one of a hierarchical set of images each representing the same conceptual picture. (NOTE: The set of images consists of one image at full resolution and other images at downsampled resolutions. This is often referred to as a MIPmap.) model  physical, mathematical, or otherwise logical representation of a system, entity, phenomenon, or process. N natural environment  the Earthbased environment modeled by an environment. node  a zerodimensional primitive used to store a significant location. north pole  that pole of rotation that lies on the north side of the invariable plane of the solar system. (NOTE: Some planets have retrograde rotation with respect to this definition. Map north may be unrelated to this direction. ) numerical value  a real number that represents a quantity. O object  conceptual structure having both type and state. object binding rule (for an ORMT)  an objectspace specific restriction for the binding of a single RD in the RD set of the ORMT. object binding rule set (OBRS)  ORMs for planets, satellites, and other celestial bodies include objectdynamic ORMs based on ORMT BI_AXIS_ORIGIN_3D. Many of these objectdynamic ORMs share common rules for the binding of ORMT BI_AXIS_ORIGIN_3D components based on physical characteristics and spatial arrangements of the applicable celestial bodies. An OBRS facilitates uniform specification of such ORMs.object life cycle  the property of being created and existing until destruction. object reference model (ORM) (for a spatial object)  a set of bound RDs for which there exists exactly one normal embedding that is compatible with each bound RD in the set. object reference model template (ORMT)  a set of RDs and binding constraints such that, for a given objectspace, whenever the RDs in the set are bound in compliance with the set of binding constraints, then that bound set of RDs forms an ORM. objectspace  an abstract universe or a real universe that is associated with a designated spatial object of interest. (Objectspace is the context in which all spatial locations are represented and spatial operations are performed. A rigid spatial object is assumed to be fixed in its objectspace.) oblique Mercator SRFT (for a sphere ORM)  an oblique Mercator and augmented oblique Mercator map projection of the sphere RD component of the ORM. obliquity of the ecliptic  the angle in radians from the equatorial plane to ecliptic. The obliquity of the ecliptic is a function of UTC time t elapsed from a given epoch. oceanographic representation  the depiction of the ocean environment, which includes data on the location and characteristics of the ocean bottom (e.g., depth curves, bottom contours, sediment types), as well as the representation of processes required to describe the natural and manmade static and dynamic surface and subsurface ocean conditions (e.g., temperature, salinity gradients, acoustic phenomena).organizational schema  end result of a process of concept characterization, comprised of a set of groups of concepts. original data  the source data utilized by a resource provider to construct their initial environmental representation. outthewindow (OTW)  human eye view of a visible spectrum environment through the viewport or window of a physical model of a tactical vehicle. P physical objects  real world objects. (The length of one metre has intrinsic meaning in the objectspace of a physical object.) physical quantity  quantity that can be used in the mathematical equations of science and technology. point feature  a geographic entity that defines a zerodimensional location. For example, a well or a building.polar stereographic SRFT  a polar stereographic and augmented polar stereographic map projection of the oblate or sphere RD component of the ORM. polygon  thematically homogenous areas composed of one or more faces. position  an element of a CS range. positionspace  an ndimensional Euclidean space, for n = 1, 2, or 3. (Positionspace serves as a vector space abstraction of objectspace so that the methods of linear algebra and multivariate calculus may be applied to spatial concepts.) positional accuracy  refers to the root mean square error (RMSE) of the coordinates relative to the position of the real world entity being modeled. Positional accuracy shall be specified without relation to scale, and shall contain all errors introduced by source documents, data capture and data processing. profile  identifies a subset of an International Standard that has been specified to meet the needs of a specific application area. projected coordinate system (PCS)  an instantiation of a coordinate transformation. A planar, righthanded Cartesian coordinate set that, for a specific map projection, has a single and unambiguous transformation to a geodetic coordinate system. property  characteristic of an object. provider  see resource providers. Q quantity  property ascribed to phenomena, bodies, and/or substances that can be used to specify either the size, the amount, or the extent of a particular phenomenon, body, and/or substance. quasiinertial direction  a direction that changes over time relatively slowly with respect to the universe. R reference datum (RD)  a geometric primitive in positionspace that is used to model an aspect of objectspace through a process termed RD binding. reference transformation (RT) (for an ORM)  a similarity transformation from the ORM normal embedding to the normal embedding of the reference ORM for that object. representational polymorphism  technique where alternate representations of the same data serve different needs. resolution  the degree of detail and precision used in the representation of realworld aspects in a model or simulation. Granularity. resource consumers  organizations that want to convert a SEDRIS transmittal generated by a provider into their database native format. resource providers  organizations that provide either complete environmental data sets, or the raw data that is used by database generation systems to produce environmental data sets. S scalability  the ability of a distributed simulation to maintain time and spatial consistency, as the number of entities and accompanying interactions increase. SEDRIS  an infrastructure technology that enables information technology applications to express, understand, share, and reuse environmental data. SEDRIS abstract transmittal format  general organization, structure, and allowable content that is required for all external representations of transmittals [ISO/IEC 180232]. SEDRIS application  any application software that can consume a SEDRIS transmittal (e.g., to view, verify, or validate the data; or to convert to a target format). SEDRIS transmittal  a particular data set that is represented in compliance with the SEDRIS data representation model for the purpose of interchange in memory or through the SEDRIS transmittal format. SEDRIS transmittal format (STF)  1: provides users of SEDRIS, both data consumers and data providers, with a means of crossplatform interchange by supplying a universally specified external storage format. 2: binary encoding of the SEDRIS abstract transmittal format [ISO/IEC 180233]. selection data type  similar to an enumerated data type but forms a set of entries that may be extended. selector  one of the values allowed by the definition of a selection item data type. semantics  the implied meaning of data. Used to define what entities mean with respect to their roles in a system. semiautomated forces (SAF)  see computer generated forces. sensor model  a model of a sensing system (sensor) other than a direct human eye visual model. It may, and usually does, include a sensor signature model, a sensor atmospheric model and a sensor effects model. It may also include human perception response for CGF simulation. Examples of sensor models include radar system models, sonar system models, FLIR (forward looking infrared) imager models, and NVG (night vision goggle) models. solar ecliptic SRFT  a spherical CS based SRF aligned with the ecliptic plane of a planet and the direction of the Sun. solar equatorial SRFT  a spherical CS based planet centred SRF aligned with the ecliptic plane and the rotational axis of the Sun. solar magnetic dipole SRFT  a Euclidean 3D CS based planet centred SRF with the zaxis aligned with the magnetic dipole and the xzplane containing the Sun. solar magnetic ecliptic SRFT  a Euclidean 3D CS based planet centred SRF aligned with the direction to the Sun and the plane determined by that direction and the magnetic dipole of the planet. source format  the data file format in which the environment is stored prior to interchange. space representation (including ionosphere)  the depiction of the space environment, which includes data on the location and characteristics of regions beyond the upper boundary of the troposphere, and including neutral and charged atomic and molecular particles and their optical properties. spatial object  physical or virtual object to which spatial information applies. spatial operation  mathematical function that reexpresses coordinates, directions, and/or distances expressed in one spatial reference frame in terms of a different spatial reference frame or a mathematical function for distance or other geometric quantities within a single spatial reference frame. spatial reference frame (SRF)  a specification of a spatial coordinate system that is constructed from an ORM and a compatible abstract CS, such that coordinates uniquely specify positions with respect to the spatial object of the ORM. spatial reference frame set (SRFS) (for an ORM)  a finite parameterized set of two or more spatial reference frames. spatial reference frame template (SRFT)  a template used to derive a spatial reference frame. state (of an object)  one of the possible modes of existence of an object as defined by the collective values of its attributes. symbol  short, scientific notation for a unit of measure or a scale factor or both. T temporal coordinate system (CS)  a Euclidean 1D CS that assigns distinct coordinates to distinct times so that larger coordinate values are assigned to later times. terrain representation  the depiction of the terrain environment, which includes data on the location and characteristics of the configuration and composition of the surface of the Earth, including its relief, natural features, permanent or semipermanent manmade features and related processes. It includes seasonal and diurnal variation, such as grasses and snow, foliage coverage, tree type, and shadow. The terrain surface includes inland waters, and the sea floor bottom to the 10meter depth curve.terrain skin  the geometrical portion of the terrain representation that model's the Earth's surface, including terrain polygons, vertices, and vertex normals. texel  single element of an image used as a texture. texture  image or a set of images applied to a surface representation to depict detail. tick mark  a point on an axis identified by a specified value. tile  one of a set of identical planar shapes that have been arranged to completely cover an area. time  that physical quantity perceived as the continued progress of existence measured by an observer as events that are relatively ordered as “before” or “after” and which, at a given point in time, give rise to the notions of past, present and future. (Time and location are often used together by an application to describe when a given condition exists or when an object was present at a given location.) token set  a special type of attribute within a SEDRIS class. It’s an attribute that can contain multiple values. topology  refers to any relationship between connected geometric primitives that is not altered by continuous transformation. transfer format  specification of the actual byte level descriptions of the physical files of a SEDRIS transmittal. transmittal  hierarchy of DRM class instances and other information organized according to the principles described in ISO/IEC 180231. transmittal file  file containing all or part of a transmittal.transmittal format  interchange format for transmittals.transverse Mercator SRFT  a transverse Mercator and augmented transverse Mercator map projection of the oblate or sphere RD component of the ORM. traversal  movement from one object to another through a relationship between them, as in crossing between nodes in graph theory. type (of an object)  essential aspects of an object that characterize and distinguish it from other objects. U unit of measure  reference quantity chosen from a category of mutually comparable physical quantities [ISO 310:1992]. universal time observed (UT0)  the mean solar time of the prime meridian obtained from direct astronomical observation. universal time polar motion corrected (UT1)  UT0 corrected for the effects of small movements of the Earth relative to the axis of rotation (polar variation). universal time Earth rotation corrected (UT2)  UT1 corrected for the effects of a small seasonal fluctuation in the rate of rotation of the Earth. universal transverse Mercator (UTM) PCS  an ellipsoidal transverse Mercator projection to which specific parameters, such as central meridians, have been applied. The Earth, between latitudes 84.0 degrees North and 80.0 degrees South, is divided into 60 zones, each generally 6 degrees wide in longitude. V validregion  a restriction of the CS domain of the generating function (or mapping equations) for a CS as used in an SRF. value (of a physical quantity)  quantitative expression of a particular physical quantity as the pairing of a real number and a unit of measure, the real number being called its numerical value. vernal equinox  the equinox at which the direction from the planet to the Sun begins to ascend to the northern side of the equatorial plane. virtual simulation  a simulation involving real people operating simulated systems. Virtual simulations inject [man]intheloop in a central role by exercising motor control skills (e.g., flying an airplane), decision skills (e.g., acquiring a target through a sensor and committing fire control resources to action), or communication skills (e.g., as members of a C4I team). W
World Geodetic
System (WGS84)  defines the current U.S. DoD standard horizontal
and vertical reference datums for a geodetic coordinate system, collected
and standardized in 1984. 
