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Since MinElevation, MaxElevation and MaxCulture components are defined, any line-of-sight algorithm can rapidly assess an intersection status of the line-of-sight vector with the terrain
andor with the cultural features of the CDB. Furthermore, since the MaxCulture component follows the same conventions as the MinElevation and MaxElevation components, it is easy for
the LOS algorithm to combine the values to determine the highestlowest point with or without cultural features in a given geographic area. The culture-variant of the LOS algorithm is
virtually identical to the terrain-only case. Before undertaking its computations, the LOS algorithm must add the values of MaxCulture to the MaxElevation values, once adjusted for
LOD, and then perform the first LOS determination based on this. If an intersection is detected with MaxCulture, the final determination of intersection is conducted at first with the bounding
box of the cultural feature, then with the actual geometry of the cultural feature if available.
Note that the geographic areas where MaxCulture is zero can be used to quickly identify the absence of any obstacles that can potentially affect the route of an entity.
The MaxCulture component also follows the “center grid data element” convention of the CDB Specification. In the case where a cultural feature has no modeled representation, the
MaxCulture component must be generated from the feature’s bounding volume that overlaps each MaxCulture grid data element. If the feature has an associated modeled representation, the
grid data of the MaxCulture component must be generated from the model geometry.
5.6.1.7.1 Level of Details
The coarser LODs of the MaxCulture component are iteratively derived from the finest generated LOD.
Since the MaxCulture component is intended to be used in conjunction with the MaxElevation component, it is recommended that the number of LODs for the MaxCulture component be equal
or greater than the MaxElevation component.
5.6.1.7.2 Data Type
Requirement 95
http:www.opengis.netspeccdb1.0core maxculture-data-type
The MaxCulture component SHALL be represented as floating-point or signed integer values. Integer values for tiles at LOD larger than 0 SHALL be scaled according to the
following formula: ��������� = ��������×2
Integer values can make use of TIFF’s 8-bit, 16-bit, or 32-bit representation.
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5.6.1.7.3 Default Read Value
If none of the LODs of the MaxCulture dataset are provided, then simulator client-devices should assume default MaxCulture values. The default values for these datasets can be found in
\CDB\Metadata\Defaults.xml and can be provided to the client-devices on demand. Handling of defaults fall under the following two cases:
● CASE I: In the case where the MaxCulture component is missing, but there is at least one vector dataset; client-devices should assume a default MaxCulture value of
Default_MaxCulture_CaseI. In the event this default value is not supplied, the CDB standard recommends that client-devices use a value of 600 m corresponding to the tip
of World’s tallest tower plus a margin of 47 m.
● CASE II: In the case where the MaxCulture component is missing, but there is not a single vector dataset; client-devices should assume a default MaxCulture value of
Default_MaxCulture_CaseII. In the event this default value is not supplied, the CDB standard recommends that client-devices use a value of 0 m.
5.6.1.7.4 Default Write Value
The files associated with the MaxCulture components for the area covered by a tile at a given LOD should not be created if the Primary Terrain Elevation data is not available.
The CDB standard strongly recommends that the MaxCulture dataset be generated in accordance to the following guidelines:
If the finest LOD of any vector tiled datasets is available at LOD ≥ 6, then all LODs ranging from -10 ≤ LOD ≤ n – 6 of the MaxCulture dataset should be generated where n is the
finest available LOD of any vector tiled datasets. The technique illustrated in Figure 5-15: Generation of LODs for the MinMaxElevation Dataset 1D should be used to populate the LOD
hierarchy. Gaps i.e., missing levels in the MIP-MAP hierarchy are not permitted. It is not permitted to generate MaxCulture dataset tiles that are partially populated with data.
If the finest LOD of any vector tiled datasets is available at LOD ≤ 5, then all LODs ranging from -10 ≤ LOD ≤ 0 of the MaxCulture dataset should be generated where n is the
finest available LOD of any vector tiled datasets. The technique illustrated in Figure 5-15: Generation of LODs for the MinMaxElevation Dataset 1D should be used to populate the LOD
hierarchy. Gaps i.e., missing levels in the MIP-MAP hierarchy are not permitted. MaxCulture dataset tiles that are partially populated with data should not be used.
5.6.1.7.5 Supported Compression Algorithm
