Table 6.216 — DRM_Reference_Surface

Property

Description

Class

  • <DRM Reference Surface>

Superclass

Subclass

  • None.

Definition

An instance of this DRM class specifies a constructed, geometric surface that is part of the environment. The <DRM Reference Surface> instance is used to determine the elevation of conforming points in the component tree rooted at each hierarchy instance of which it is a component. Conforming points are either <DRM Location 2D> instances or <DRM Location Surface> instances. A <DRM Reference Surface> instance also specifies how the surface is used in determining the elevation value.

An instance of <DRM Feature Hierarchy> or <DRM Geometry Hierarchy> requires a <DRM Reference Surface> component if the following conditions apply:

  1. There are conforming points below the hierarchy.
  2. The conforming points are in the scope of a 3D SRF.
  3. The data provider wants the locations to lie on a surface other than the last default surface. The initial default is the designated spatial surface specified in the corresponding srf_context_info field. If no designated spatial surface is specified, the surface of the ORM specified for the SRF is used.

The field values of the <DRM Reference Surface> instance in conjunction with its associated <DRM Geometry Hierarchy> instance define a surface for determining the elevation values for conforming points. There are several cases:

  1. The <DRM Geometry Hierarchy> instance is a <DRM Property Grid Hook Point> instance that has at least one <DRM Property Grid> component G with these qualifications:

    1. the <DRM Classification Data> component of G matches the classification field of the <DRM Reference Surface> instance,
    2. G has two spatial axes corresponding to the horizontal coordinates of the SRF, and
    3. G has a <DRM Table Property Description> component for height, elevation, or bathymetry.

    If the <DRM Property Grid> instance meets the above criteria, it defines a reference surface.

  2. The <DRM Geometry Hierarchy> instance is a <DRM Union Of Primitive Geometry> instance that aggregates <DRM Surface Geometry> components with <DRM Classification Data> instances matching the classification field of the <DRM Reference Surface> instance. In this case, all such <DRM Surface Geometry> components combine to form the reference surface.

  3. The <DRM Geometry Hierarchy> instance is a <DRM LOD Related Geometry> instance that aggregates (directly or indirectly) <DRM Geometry Hierarchy> instance cases a and/or b above under an LOD branch selected by the lod_rule field of the <DRM Reference Surface> instance. The <DRM LOD Related Geometry> instance may be of type distance, index, map scale, or spatial resolution. The branch selected by the lod_rule field forms the reference surface.

  4. The <DRM Geometry Hierarchy> instance aggregates some combination of cases a, b, or c. For each such case, the combination of the individual reference surfaces forms the composite reference surface.

The third coordinate-component of a conforming point is determined as specified in 4.7.3 Location.

Within the reference surface, only geometry matching the (possibly elaborated) classification specified by the classification field is used.

The multiplicity_rule field specifies a rule to select a single point from multiple intersections of a ray with the reference surface defined by the instance of <DRM Reference Surface>.

The lod_rule field specifies a rule to select one LOD branch.

Class diagram

Figure 6.266 — DRM_Reference_Surface

Inherited field elements

Field name

Range

Field data type

None

   

Field elements

Field name

Range

Field data type

classification

 

EDCS_Classification_Code

multiplicity_rule

 

Reference_Surface_Elevation_Select

lod_rule

 

Reference_Surface_LOD_Select

Default field values

Default field values for DRM_Reference_Surface

Associated to (one-way) (inherited)

  • None.

Associated to (one-way)

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)

  • None.

Composed of (two-way)

Composed of (two-way metadata) (inherited)

  • None.

Composed of (two-way metadata)

  • None.

Component of (two-way) (inherited)

  • None.

Component of (two-way)

Constraints

Clarifications

1This specifies the <DRM Geometry Hierarchy> instance containing the <DRM Surface Geometry> instances and/or <DRM Property Grid> instances to be used as the reference surface.

2A <DRM Reference Surface> instance has <DRM Property Value> components only when the classification of the <DRM Reference Surface> requires elaboration by <DRM Property Value> components.

Example(s)