Geoscience Reference
In-Depth Information
Fig. 1
Based on Table
1
,
percentage of explicit
metadata (number of “E”s per
total number of information
fields) in
blue
versus implicit/
none metadata (“I” and “Ø”)
in
pink
for each inventoried
portal. Results are from the
original inventory in mid-
2013
number of information fields) in blue versus implicit/none metadata (“I” and “Ø”)
in pink for each inventoried portal.
The following notes present some of the facts which may be outlined from this
inventory:
• The metadata which outline 3D models are uncommon and inconsistent, thus
difficult to be reasoned
- In Table
1
, there is no metadata filed which is “E” under the entire inven-
toried portal. This implies that it is impossible to document the same 3D
model according to similar parameters. For example, for outlining LoD,
Scale
(explicit under CGDI),
Object Count
(explicit under CBW, CTY1, and
CTY2) and
Primitive Count
(explicit under CBW and TRL) are not inter-
changeable or necessarily correlated.
- The concept of LoD is attributed with different explicit and implicit state-
ments as
Scale
in 1,
Object Count
in 3, and
Primitive Count
in 3 of the 8
inventoried metadata. Table
1
demonstrates that none of the portals which
are dedicated to sharing 3D models (by the definition of their governors)
use scale as an indicator of LoD. Besides, thematic-geometric LoDs such as
CityGML LoD were never noticed even at implicit level.
- The literature shows that certain practices look for particular indicators when
searching 3D models. For some examples one may refer to
Vertical Reference
and
Coverage
for 3D integration,
Vertical Precision
,
Elevation Encoding
,
and
Proprietary Format
for 3D analysis, and
3D Appearance
for 3D visuali-
zation. But, as indicated by Table
1
, except
Proprietary Format
and
Vertical
Precession
which are respectively explicit in 6 and 4 of the 8 inventoried
metadata, most of the inventoried portals (6 of 8) never document the rest of
the mentioned indicators explicitly.
•3D models are dificult to discover and to compare according to their geometric
specifications:
- The dimension of the contained geometric primitives is never attributed
explicitly despite its importance in defining the geometric dimension of
