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 that always appear before any other <DRM Axis> instances in its ordered list of <DRM Axis> instances.

A spatial axis is a <DRM Axis> instance that describes sampling along one of the components of the spatial reference frame 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> instance shall match the spatial reference frame exactly, using a consistent specification (e.g., the same ORM, direction vector and (possibly scaled) units.

1. The spatial <DRM Axis> instances of a <DRM Property Grid> instance shall always be the first members of the ordered set of <DRM Axis> components. The spatial_axes_count field indicates how many of the <DRM Axis> instances are spatial. Because the <DRM Axis> instance 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> instances. If a producer has a choice, it is recommended that spatial <DRM Axis> components be ordered in the same way as the spatial reference frame components, but as mentioned in a. above, this is not always possible, so no assumptions can be made about the ordering apart from those stated above.

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

This specifies up to three grid indices 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 given <DRM Property Grid> instance.

The identified cell is the attachment cell of the given <DRM Property Grid> instance; it 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 given <DRM Property Grid> instance; that is, the indices shall be within the appropriate bounds of the <DRM Property Grid> instance. Only the first spatial_axes_count entries of location_index are significant. This specifies the SRF within which the given <DRM Property Grid> instance is defined, rather than attempting to depend on the SRF of the context in which the instance appears.

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 a SRF in which the data positions form a grid.

If data_present = TRUE (the default), the given <DRM Property Grid> instance contains cell values that can be extracted by invoking the appropriate API functions. Otherwise, if data_present = FALSE, the given <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.

Class diagram

Figure 6.224 — DRM_Property_Grid

Constraints

• Axis type restrictions
• Index codes within tables
• Non crossing associations
• Publishable Object

Example(s)

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

• Consider a <DRM Property Grid> instance classified as ECC_WATER_BODY_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 would provide an empty <DRM Property Grid> instance, attaching it to the hierarchy with a <DRM Property Grid Hook Point> instance, as usual, with the following structure.

  

  Figure 6.225 — <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.