55
© 2016 Open Geospatial Consortium
Requirement 27
http:opengis.netspecCDB1.0cor esem-base-material
The specialist SHALL ensure that his SEM has a corresponding Base Material for each of the CDB Base Materials.
2.5.5 Generation of Materials for Inclusion in CDB Datasets
In the case of vector data, the generation of the material information typically requires the modeler to apply an image classification process to the terrain raster imagery. Many industry-
standard tools offer this classification capability.
Following this step, the resultant material classified raster imagery is vectorized into polygons polygons andor lineals. Note that the quality of the image classification typically improves
with the availability of multispectral terrain imagery data. Also note that these two steps can be skipped if the vectorized datasets already exist in digital form.
The classification of the terrain imagery can be done directly against the Base Materials defined by \CDB\Metadata\Materials.xml. In this case, the modeler need not be aware of the mandated
Base Materials. This can be done because the tools can abstract these Base Materials and provide the modeler with an alternate selection of materials. The selection of materials provided
to the modeler is quite arbitrary. This indirect step allows modelers to work with the “materials” they are familiar with. Nonetheless, the tools must, in the end, build the Composite Material
Tables required by the CDB standard and resolve all material references into the Base Materials supported by this Standard. In effect, the Composite Material Table is used to map the modeler’s
materials into CDB Base Materials.
Alternately, the classification of the terrain imagery can be done against whatever “material classes” modelers are accustomed to use when conducting such classifications. In this case, the
SEM specialist can define corresponding Composite Materials for each of these material classes so that they resolve down to the Base Materials supported in the CDB data store.
Requirement 28
http:opengis.netspecCDB1.0cor egeneration-materials-3d
In the case of 3D models, the modeler SHALL appropriately tag zones or selected polygons with the appropriate materials. Here again, the modeler need not be aware of
the Base Materials mandated by the CDB standard and can work with the materials he is
56
© 2016 Open Geospatial Consortium
most familiar with.
3. CDB Structure
This chapter defines the CDB data store physical structure, i.e., the name of all directories forming the CDB model hierarchy, as well as the name of all files found in the CDB model
hierarchy. An important feature of the CDB Model is the fact that all CDB file names are unique and that the filename alone is sufficient to infer the path to get to the file.
The CDB is composed of several datasets that usually reside in their own directory structure; however some datasets share a common structure. The following sections present the directory
structures for all CDB conformant datasets.
3.1 Top Level CDB ModelStructure Description
The top-level directory structure of the CDB from the root directory is described below. All of the synthetic environment content falls in these directories:
1. \CDB\:
This is the root directory of the CDB. It does not need to be “\CDB\” and can be any valid path name on any disk device or volume under the target file system it is stored on.
In order for the text of this standard to remain readable, all examples referring to the root CDB path name will start with \CDB\. A CDB cannot be stored directly in the root
directory of a disk device or volume. A CDB path name cannot be within another CDB or CDB version. The length of the path name leading to the CDB root directory should
be small enough such that the platform file system can store all possible file path names stored within a CDB.
Requirements Class 29-32 req
corecdb-root-requirements Target type
Data instance Dependency
XML Dependency
CDB file hierarchy Dependency
XML Schema – Part 2
