Geoscience Reference
In-Depth Information
models, the user needs to study hundreds of descriptive tags, written summaries, and
community specific expressions. Such issues have existed since the early days of
online data sharing (Létourneau et al.
1998
) and been inherited by the present-day
dissemination of 3D models. Indeed, Evans (
2012
), Pu et al. (
2007
), and Funkhouser
et al. (
2002
) indicate that finding the existing 3D models is a challenging task.
Therefore, as 3D geospatial models are widely produced and stored in vari-
ous personal and official databases and file systems (Stoter et al.
2013
; Terrace
et al.
2012
; Breunig and Zlatanova
2011
), metadata plays an important role in
sharing and seeking them (Evans
2012
; Cellary and Walczak
2012
; Dietze et al.
2007
). Metadata is known to be a key component to publish and discover geospa-
tial resources (Rajabifard et al.
2006
; Longhorn
2005
; Ramroop
2004
). Metadata
describes various specifications of geospatial resources such as the respective affil-
iations, extent, and geospatial content. Despite the general standardization of geo-
spatial metadata like in ISO 19115 and its community extensions, several practices
indicate that effective dissemination of 3D geospatial models requires specific
metadata (Uden and Zipf
2013
; Schilling et al.
2007
; Zipf and Tschirner
2005
;
Anan et al.
2002
). Funkhouser et al. (
2002
) indicate that failure in discovering 3D
geospatial models (i.e. flood of irrelevant matches or empty search results) is due
to ambiguous or irregular metadata. To avoid the costly malfunctions of the down-
loaded or purchased 3D models such as incompatibility with the applied analytic
and rendering tools (Terrace et al.
2012
), 3D communities like Unidy3D (
forum.
unity3d.com
), Layar (
devsupport.layar.com/forums
), and mp3Car (
mp3car.com/
vbulletin
) forums warn users not to retrieve 3D models without sufficiently know-
ing about their specifications. In fact, it is easy to misinterpret an unstructured set
of 3D specifications like mistaking 3D coordinates for 3D model (Scianna
2013
),
2.5D triangulated network for 3D mesh (Ledoux and Meijers
2011
), and adjacent
set of polygons in 3D space for volumetric object (Scianna
2013
; Penninga
2008
).
Hence, in response to the mentioned issues and anticipating the true open market
of 3D geospatial models, we brought up two principal questions to investigate.
First, where can 3D geospatial models be published and discovered? Online
geo-portals and commercial catalogues are among the popular options. Some geo-
portals like the Discovery Portal of the Canadian Geospatial Data Infrastructure
(CGDI) are open to every type and theme of geospatial resources. Some like
Trimble (Google) 3D Warehouse and 3D CAD Browser are exclusive to specific
types of 3D models.
Second, which metadata are used to describe 3D geospatial models? Flotynski
and Walczak (
2013
) describe the semantic of 3D web contents. Focusing on X3D
graphics, they overlook other types of 3D models. The 3D metadata framework
by Doyle et al. (
2009
) documents 3D anatomy objects and is short on 3D geospa-
tial domain. Boeykens and Bogani (
2008
) use their specific metadata to document
3D architectural repositories. However, they build their metadata with reference to
specific type and format of such repositories (i.e. Trimble/Google 3D Warehouse).
Dietze et al. (
2007
) are closer to mass dissemination of 3D geospatial models as
they extend ISO 19115 which is a generic metadata standard. But, their exten-
sion remains exclusive to city models and mainly focuses on CityGML (CityGML
