Table 6.229—DRM_Reference_Vector

Property

Description

Superclass

· <DRM Base Reference Vector>

Class

· <DRM Reference Vector>

Subclass

· none

Definition

An object of this DRM class specifies a unit vector that is used to specify a direction, normal, or axis in the manner specified by the vector_type field. It serves as a unit vector in those coordinate systems with compatible vector space structure. In GD, GM, GEI, GSE, GSM, and SM coordinate systems, it is a vector in the canonical LTP at the location of the <DRM Reference Vector> <DRM Location> component.

Example(s)

· A <DRM Reference Vector> contained by a <DRM Polygon>, representing its geometric normal vector. This would have a vector_type of FACE_NORMAL.

· A <DRM Reference Vector> contained by a <DRM Polygon>, representing a normal vector that is used for rendering purposes, i.e., to calculate color and shading when rendering the <DRM Polygon>. This <DRM Reference Vector> would have a vector_type of RENDERING_NORMAL.

· A fence modeled as a polygon has radar cross sections that are dependent on aspect angles (azimuth and elevation). These aspect angles are defined with respect to the polygon's normal and its azimuth <DRM Reference Vector>. This <DRM Polygon> (fence) has two <DRM Reference Vector>s (a geometric-normal and an azimuth-reference). The geometric normal is the unit vector perpendicular to the <DRM Polygon> pointing away from it on its outside face and the azimuth reference vector points straight up and is in the plane of the <DRM Polygon>.

· A segment of the road has a reflector (actually, a retro-reflector) on it and is modeled as a <DRM Line>. The <DRM Line> has a normal vector that is perpendicular to it and an azimuth reference parallel to it. This is sufficient to describe radar cross sections of the road as a function of aspect angles. However, the normal vector for the infrared bands depends on the orientation of the retro-reflector, not the road. This because radars see the road but IR (or more obviously, car lights) see the retro- reflector. In this example, the <DRM Line> has four <DRM Reference Vector>s (radar-normal, radar-azimuth, ir-normal, and ir-azimuth).

· A normal vector used for reflectivity/emissivity calculations. This would have a vector_type of REFLECTIVITY_EMISSIVITY_NORMAL.

· A vector specifying the direction an Infinite Light illuminates. This would have a vector_type of LIGHT_DIRECTION.

Inherited field elements

field_name	range	Field_Data_Type
none

Field elements

field_name	range	Field_Data_Type
unit_vector		Vector_3
vector_type		Reference_Vector_Type

Associated to (one-way) (inherited)

· none

Associated to (one-way)

· none

Associated by (one-way) (inherited)

· none

Associated by (one-way)

· none

Associated with (two-way) (inherited)

· none

Associated with (two-way)

· none

Composed of (two-way) (inherited)

· zero or one <DRM Location>

· zero or one DRM_Reference_Vector_Control_Link

Composed of (two-way)

· none

Composed of (two-way metadata) (inherited)

· none

Composed of (two-way metadata)

· none

Component of (two-way) (inherited)

· none

Component of (two-way)

· zero or more <DRM Base Vertex>s

· zero or more <DRM Cylindrical Volume Extent>s

· zero or more <DRM Ellipse>s

· zero or more <DRM Elliptic Cylinder>s

· zero or more <DRM Infinite Light>s

· zero or more <DRM Line>s

· zero or more <DRM Lobe Data>s

· zero or more <DRM LSR Transformation Step>s

· zero or more <DRM Moving Light Behaviour>s

· zero or more <DRM Parallelepiped Volume Extent>s

· zero or more <DRM Point>s

· zero or more <DRM Polygon>s

· zero or more <DRM Union Of Geometry>s

Constraints

· Inheritence rule for Location

· Required Reference_Vector location

Notes

none

Class diagram

<DRM Reference Vector>