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The MinElevation and MaxElevation components 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.
5.6.1.6.3 Default Read Value
The Line-of-Sight algorithm is described in Section 8 Volume 0 - CDB Primer Formerly Appendix A. Note that the algorithm starts with the coarsest LOD of the MinMaxElevation
dataset; the algorithm recursively executes with progressively finer level-of-detail versions of the MinMaxElevation dataset until the algorithm decides it no longer needs to access finer levels or
until the algorithm no longer finds finer levels of the MinMaxElevation dataset.
If none of the LODs of the MinMaxElevation dataset are provided, then simulator client-devices SHOULD assume default MinElevation and MaxElevation 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 falls under the following two cases:
● CASE I: In the case where the tile-LOD for the MinElevation and the Primary Terrain Elevation components are both missing, the CDB Specification recommends a default
setting of Default_MinElevation_CaseI = Default_Elevation-1. Similarly, where a tile- LOD for MaxElevation and the Primary Terrain Elevation components are both missing,
the CDB standard recommends a default setting of Default_MaxElevation_CaseI = Default_Elevation-1.
● CASE II: In the case where the tile-LOD for the MinElevation is missing and the
Primary Terrain Elevation is not missing, the CDB standard recommends a default setting of Default_MinElevation_CaseII = as supplied in Defaults.xml. In the event where this
default value is not supplied, the CDB standard recommends that client-devices use a default value of -400 m corresponding to the shore of the Dead Sea for MinElevation.
Similarly, when MaxElevation is missing and the Primary Terrain Elevation is not missing, the CDB standard recommends a default setting of Default_MaxElevation_CaseII = as supplied in
Defaults.xml. In the event this default value is not supplied, the CDB standard recommends that client-devices use a default value of 8846 m corresponding to the peak of Mount Everest for
MaxElevation.
5.6.1.6.4 Default Write Value
The files associated with the MinElevation and MaxElevation 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 recommends that the MinElevation and MaxElevation components be generated in accordance to the following guidelines:
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● If the finest LOD of the Primary Terrain Elevation component is available at LOD ≥ 4, then all LODs ranging from -10 ≤ LOD ≤ n – 4 of the MinElevation and MaxElevation
components should be generated where n is the finest available LOD of the Primary Terrain Elevation component. 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 MinElevation and MaxElevation components tiles that are partially populated with data.
● If the finest available LOD of the Primary Terrain Elevation component is available at LOD ≤ 3, then all LODs ranging from -10 ≤ LOD ≤ 0 of the MinElevation and
MaxElevation components should be generated. 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 MinElevation and MaxElevation components
tiles that are partially populated with data.
In the event where parts of a MinElevation tile cannot be determined due to missing primary elevation tiles, the CDB standard recommends to use a default value of
Default_MinElevation_CaseIII, -400 m corresponding to the shore of the Dead Sea for MinElevation. Similarly, in the event where parts of a MaxElevation tile cannot be determined
due to missing primary elevation tiles, the CDB Specification recommends to use a default value of Default_MaxElevation_CaseIII, 8846 m corresponding to the peak of Mount Everest for
MaxElevation. Figure 5-19: Missing MinMaxElevation Datasets shows this case:
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Figure 5-19: Missing MinMaxElevation Datasets
5.6.1.6.5 Supported Compression Algorithm
