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Negative elevation values do not imply that the elevation point is submerged; rather, a negative value merely indicates that its altitude is below the WGS-84 reference ellipsoid.
The CDB standard defines a number of subordinate elevation components that are used in combination with the primary component of the Elevation Dataset.
5.6.1.1 Terrain Mesh Types
The CDB standard defines two mesh types to connect each grid post to its neighbors. The purpose of the mesh type is to minimize the error in the representation of the Terrain Profile built
from the components of the Elevation dataset. Figure 5-7 below illustrates the supported CDB Mesh Types.
Figure 5-7: CDB Mesh Types
Mesh type 0 connects the southwest grid post to its northeast neighbor while mesh type 1 does the same for the northwest and southeast posts.
5.6.1.1.1 Data Type
The mesh type is represented by an unsigned integer of a size that is large enough to accommodate the range of mesh types. Currently, there are only two values defined; as such, an
8-bit unsigned integer is sufficient and appropriate to store the mesh type.
5.6.1.1.2 Default Value
By default, when the mesh type is not specified or not available, a value of zero is assumed.
5.6.1.2 List of all Elevation Dataset Components
The Elevation Dataset is comprised of several components listed here and detailed in the subsequent sections.
Mesh Type 0 Mesh Type 1
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Table 5-11: Elevation Dataset Components CS1
CS2 File
Extension Component
Name Component
Description Dataset 001, Elevation
001 001
.tif Primary
Terrain Elevation
A grid of data representing the Elevation at the surface of the Earth. Stored as a 1 or 2-channel
TIFF image. When present, the second channel provides the mesh type of each grid element.
001 002
.tif Primary
Terrain Elevation
Control Deprecated
001 003
.tif Primary
Alternate Terrain
Elevation A grid of data representing the Elevation of the
surface of the Earth at specified Latitude and Longitude offsets inside each grid element. Stored
as a 4-channel TIFF image.
002..099 001
.tif Subordinate
Terrain Elevation
Deprecated 002..099
002 .tif
Subordinate Terrain
Elevation Control
Deprecated
100 001
.tif Subordinate
Bathymetry A grid of data representing the Depth of water with
respect to the selected Terrain Elevation component. Store as a 1 or 2-channel TIFF image.
When present, the second channel provides the mesh type of each grid element.
100 002
.tif Subordinate
Alternate Bathymetry
A grid of data representing the Depth of water at specified Latitude and Longitude offsets inside
each grid element with respect to the selected Terrain Elevation component. Stored as a 4-
channel TIFF image.
101 001
.tif Subordinate
Tide Elevation
A grid of data representing the average height variation of water with respect to the Primary
Terrain Elevation Component. Dataset 002, MinMaxElevation
001 001
.tif Minimum
Elevation Minimum height on a per tile LOD basis of the
Primary Terrain Elevation Dataset Component excluding all cultural features.
001 002
.tif Maximum
Elevation Maximum height on a per tile LOD basis of the
Primary Terrain Elevation Dataset Component excluding all cultural features.
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001 001
.tif Primary
Maximum Culture
Elevation Maximum height on a per tile LOD basis of the
bounding boxes of all cultural features held in the vector tiled datasets within the geographic footprint
of the area represented by the sample value.
5.6.1.3 Primary Terrain Elevation Component
