Geoscience Reference
In-Depth Information
geospatial models. In Table
1
,
Primitive Dimension
was noted in 7 of the 8
inventoried metadata while implicit (i.e. “I”) in all 7 cases.
- The type of the geometric primitives (e.g. simple and composite polygons and
solids, voxel, and etc.) which constitute geospatial representations is explic-
itly documented in half of the inventoried metadata. In Table
1
,
Primitive Type
under
Information Details
column is explicit (i.e. “E”) in 4 of the 8 invento-
ried metadata and implicit (i.e. “I”) in 3 of them. But, the implications such
as
Polygon
,
3D Face
, and
Multi
-
Patch
which are used with
Primitive Type
are
often related to proprietary definitions at software specific level.
- To interpret the proprietary metadata on 3D geometric specifications (as
discussed for
Primitive Dimension
and
Primitive Type
in previous points), the
user at least needs to learn about the proprietary 3D modeling environments
and functions which have been employed. But,
3D Pre
-
Processing
(under
Information Details
in Table
1
) is only explicit in 1 of the 8 inventoried meta-
data. So, there is no guarantee that the users become aware of the proprietary
logic which is behind the presented 3D models.
• Table
1
clearly shows that more than half of the noticed metadata are implicit.
Implicit information are not formally described and make believe that 3D meta-
data are based on individual initiatives, thus inconsistent and ultimately confusing:
- Expect CGDI, the rest of the inventoried metadata are explicit on less than
half of the 3D metadata topics (Fig.
1
). Excluding CGDI with the explicitness
rate of 58 %, the average explicitness rate of the remaining metadata is 21 %
with the highest at 42 % (CBW) and the lowest at 8 % (QCOD and MRN).
4 Proposal of 3D Metadata
The inventory, as well as the literature, indicates that the metadata which is used
to document 3D geospatial data is not explicit and unifying about many key top-
ics such as the notion of dimension, contextual information, and level of details.
The following section proposes a top-level 3D metadata that aims at improving the
explicitness and integrity of the information to document 3D geospatial data. This
means that the proposal.
• Institutes the meaning and organization of 3D metadata requirements in a set of
explicit and disciplined classes, fields, and relationships (e.g. number of vertices
as primitive count and a measure of LoD);
• Avoids implicit syntaxes like creating summary-type ields which append meta-
data arbitrarily.
Regarding explicitness as a key point, the proposed 3D metadata considers the
academic and pragmatic points of view by citing more than 60 papers, standards,
and software environments as well as the inventory results. In such sense, a variety
of domains including geology, urbanism, cadaster, topographic mapping, and com-
puter graphics have been cited. These resources were investigated to identify the
