Geoscience Reference
In-Depth Information
(and distinctively) under
LOD Particular
abstract class (e.g. CityGML LoD 3 and
CIC/BIM Information LoD A).
Consistency between levels of documentation:
Some of the metadata classes in
Fig.
2
such as the
Thematic Keyword (TH_KH)
and the
GDS
classes are related
to each other with 0 to N associations. When metadata is generated at detailed
granularity (e.g. multiple instances of
MD_TRGT
class for each layer of a dataset
or theme of a semantic model), every instance of these metadata classes become
coupled with their correspondences coherently and automatically (e.g. layer X is
building and modeled by B-Rep solid
+
Layer Y is terrain and modeled by TIN).
But, when metadata is roughly defined (e.g. dataset Z represents building and ter-
rain and contains polygons and 3D points), the 0-N associations help to relate the
corresponding information. In fact, for some important metadata topics, the pro-
posed 3D metadata tries to preserve the information as explicit as possible no mat-
ter the level of
MD_TRGT
class.
5 Comparing the Proposed 3D Metadata with CGDI
Discovery Portal
For the first validation attempt, CGDI Discovery Portal was selected for being
compared with our 3D metadata because of the following reasons:
• CGDI Discovery Portal metadata partially conforms to North American Proile
(NAP) of ISO 19115.
• Regarding the importance of the explicit 3D metadata, CGDI Discovery Portal
provides the highest rate of explicit fields according to Table
1
.
• Among Canada's oficial geo-portals, CGDI Discovery Portal is the one which
permits the greatest variety of stakeholders (all levels of government organi-
zations, academia and research groups, private enterprises, and individuals) to
publish their geospatial resources.
From a conceptual point of view, the proposed 3D metadata is 100 % explicit on
every detail of the inventory table while CGDI's rate is 58 %. It is important to
know that these rates do not advocate the linguistic terminologies (e.g. match-
ing or non-matching words), but the concepts for which the metadata topics are
accounted. In such sense, the proposed 3D metadata brings up six new concepts
for documenting 3D geospatial content with
CTXT_3D
,
GDM
,
LOD
,
GMM
,
AGV
, and
TP_3D
classes from Fig.
2
, organizing 38 properties, and 97 suggested
domain value.
Here is an example to show how a new metadata concept of the proposed
3D metadata adds to the conceptual value of a common metadata topic. Scale
is a common topic which is found in both of the comparing metadata. In CGDI
Discovery Portal, scale refers to the denominator of a vulgar fraction and is an
