Geoscience Reference
In-Depth Information
- In Scenario 1, CGDI Discovery Portal is not capable of responding to the
inquiry about LoD because its respective metadata does not institute the con-
cept. On the contrary, the proposed 3D metadata defines LoD as a new meta-
data concept for documenting various aspects of data granularity.
• Conceptual specializations by the proposed 3D metadata
- In Scenario 2, both metadata are explicit on defining the concept of vertical
references. But, the proposed 3D metadata offers a more specific point of
view with enriching the concept with auxiliary and arbitrary vertical refer-
ence which may be used in 3D models.
- In Scenario 3, both metadata documents the processing background of the
dataset. However, the proposed 3D metadata decomposes this into two dis-
tinguished components;
Geometric Modeling Mechanism (GMM)
class
specifically for 3D modeling background and
Manipulation Background
(MNP_BCK)
class for classic cartographic procedures.
• Syntactic advantages of the proposed 3D metadata
- In Scenario 2, CGDI Discovery Portal permits one vertical reference per
metadata. This shortcoming is not present in the proposed 3D metadata as
the maximum cardinality of
Vertical Geospatial Reference
(
VGR
) class is not
limited.
- In Scenario 3, CGDI Discovery Portal offers one summary-form field for
documenting the processing background. But, the proposed 3D metadata uses
several explicit fields to avoid implicit texts as much as possible.
6 Conclusion and Future Work
Many individuals and agencies intend to cut or reduce re-production costs by dis-
covering exiting 3D geospatial models when applicable. The literature and prac-
tical experiences clearly show that mass dissemination of such models requires
particular metadata. However, in the absence of generically conceptualized 3D
metadata, various application and domain specific documentations become frag-
mented. This problem is observed among several topics such as the context of 3D,
expression of geometric dimension (i.e. definition of “3” and “D”) and structures,
and levels of details. This results in empty or irrelevantly overloaded discovery
results when the users who seek 3D geospatial resources outline their demands
by distinct rationalities. An inventory on eight online metadata which are used to
publish and discover various 3D geospatial resources shows that the 3D geospatial
content is documented by proprietary concepts and uncommon information. The
inventory studied the published metadata against a list of 3D metadata require-
ments identified from a broad review of literature. The objective was to know how
these topics are documented; in explicitly defined fields, by chance in written sum-
maries (i.e. implicit), or not at all (i.e. none). The results (Table
1
) show that 7 of
the 8 inventoried metadata are explicit on less than half of the 12 metadata topics
(
Information Detail
column of Table
1
) with the average rate of explicitness only
