Class

• <DRM Property Grid>

Superclass

• <DRM Data Table>

Subclass

• None.

Definition

An instance of this DRM class is a <DRM Data Table> instance that has at least one but not more than three spatial axes. Spatial axes shall always appear before any other <DRM Axis> components in the ordered list of <DRM Axis> components for the <DRM Property Grid> instance.

A spatial axis is a <DRM Axis> component that describes sampling along one of the components of the SRF of the <DRM Property Grid> instance. Hence, it is directly useful for locating the sample values in space. To qualify as spatial, the <DRM Axis> component shall match the SRF exactly, using a consistent specification (e.g., the same ORM, direction vector and units). Spatial axes have the following characteristics.

1. The spatial <DRM Axis> components of a <DRM Property Grid> instance shall always be the first members of the ordered set of <DRM Axis> components. The spatial_axis_count field indicates how many of the <DRM Axis> components are spatial. Because the <DRM Axis> component ordering also determines the scanning order when data is retrieved from a <DRM Data Table> instance, placing the spatial axes first imposes some limitations on the way data can be scanned.
2. There are no other ordering rules for spatial <DRM Axis> components. If a producer has a choice, it is recommended that spatial <DRM Axis> components be ordered in the same way as the SRF components. As mentioned in the previous item, this is not always possible. Thus, no assumptions can be made about the ordering apart from those stated above.

The spatial_axis_count field specifies how many axes of the <DRM Property Grid> instance are spatial axes.

The location_index field specifies up to three grid indexes that identify the grid cell that contains the location corresponding to that specified by the <DRM Location 3D> component of the <DRM Property Grid Hook Point> aggregate of the <DRM Property Grid> instance. The identified cell is where the <DRM Location 3D> instance is attached to the <DRM Property Grid> instance. The location_index shall specify a valid cell within the <DRM Property Grid> instance; that is, the indexes shall be within the appropriate bounds of the <DRM Property Grid> instance. Only the first spatial_axis_count entries of location_index are significant.

The srf_context_info field specifies the SRF within which the <DRM Property Grid> instance is defined. The griddedness of spatial positions is dependent on the properties of the SRF. Coordinate conversions and transformations are not, in general, linear, so that a set of points that form a regular array of positions in one SRF may not be regular in another SRF. Therefore, in order to preserve griddedness, a <DRM Property Grid> instance specifies an SRF in which the data positions form a grid.

If data_present = TRUE (the default), the <DRM Property Grid> instance contains cell values that can be extracted by invoking the appropriate API functions. Otherwise, if data_present = FALSE, the <DRM Property Grid> instance does not contain any cell values although it may provide everything else that a populated <DRM Property Grid> instance can provide.

The relative_to_hook_point field specifies whether the cell data of the <DRM Property Grid> instance is specified relative to the context of a <DRM Property Grid Hook Point> instance that references it.

Class diagram

Figure 6.235 — DRM_Property_Grid

Constraints

• Constraints on associates
• <DRM Presentation Domain> constraints
• <DRM Property Grid> constraints
• Index codes within tables
• Publishable object
• Spatial axis constraints

Example(s)

• A DTED <DRM Property Grid> instance is associated to <DRM Areal Feature> instances representing DTED accuracy areas supplemental to the grid.

• Consider a <DRM Property Grid> instance classified as ECC_WATERBODY_TEMPERATURE_PROPERTY_SET for an ocean volume. Ocean temperature features, such as warm/cold currents, fronts, and eddies, are associated to specific cells of the <DRM Property Grid> instance.

• Consider a transmittal provided by a data producer whose format uses polygons rather than grids to represent terrain, where the polygons define a default post spacing. To provide this default post spacing in the transmittal, the data provider provides an empty <DRM Property Grid> instance, attaching it to the hierarchy with a <DRM Property Grid Hook Point> instance, as usual, with the structure depicted in Figure 6.236.

  

  Figure 6.236 — <DRM Property Grid> example

  The spatial <DRM Axis> instances define the extents and the spacing of the <DRM Property Grid> instance. The data provider has the option of providing <DRM Property Characteristic> components for the <DRM Table Property Description> instance to supply the minimum and maximum elevation values.