International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
on existing conditions, it is not likely that these deliberations
will yield major solutions to the current lack of access and
distribution of global satellite data and associated information
to all nations and their citizens. However, there is ample
evidence that as the GEO community improves their
formatting and access policies, 3-D Geobrowsers will be in
position to facilitate the free and equal distribution and
application of these vast global archives.
2. THREE-DIMENSIONAL GEOBROWSERS
2.1 Field of Dreams
In March of 2000, a meeting of the Digital Earth Interagency
Working Committee was convened to review the status and
prowess of 3-D visualization technologies in generating virtual
reality simulations for the Earth. A significant cross section of
industrial, governmental, and academic systems was debuted
at this milestone event. This community of supporters easily
accepted the spinning globe technologies as the iconic symbol
for Digital Earth. This amplified the vision presented by
former Vice President Al Gore in his historic speech. At that
time in the evolution of the Digital Earth initiative there was
only a general agreement as to what should be expected of
these 3-D Geobrowsers (although they were simply given the
term of Digital Earth visualization). Performance
specifications were relegated to the catchall for open systems
and interoperability protocols set out in the Digital Earth
Reference Model (DERM). As a result, progress of the dozen
or so systems continued with minimal attention to standards
for performance. Each system developer operated more or less
under the philosophy of “if we built it, people will come and
use it.”
2.2. African GIS Realities
In November of 2001, at the 5* African GIS Conference in
Nairobi, Kenya, the United Nations Environment Programme
contracted with one of the leading Geobrowser developers,
Keyhole Technology, Inc. to provide the first. international
display of an operational Geobrowser. This system streamed
data from globally distributed servers to provide a stunning
display of global satellite coverage of the Earth's surface
including the overlay of database resources upon the spherical
tessellation of a virtual globe, Figure 1. As the audience
included government and industry leaders from around the
globe, the impact of this milestone presentation cannot be
overstated.
Ld
ger THB
Figure 1. First international debut of 3-D Geobrowser.
2.3. Chinese Interest Continue Legacy
The Chinese Academy of Sciences (CAS) picked up the
Digital Earth mantle and founded the International Symposium
on Digital Earth series. In addition to their stalwart support for
an international collaboration on Digital Earth technologies,
the Chinese began a robust engagement with national,
provincial, and municipal Digital Earth projects. Until 2002,
however, the application of 3-D Geobrowsers was limited to
visualization demonstration. In December of that year, the
CAS hosted the 1% International Society for Digital Earth
workshop on 3-D Geobrowsers. This meeting brought
together representatives from many of the Geobrowser
development teams including Japan and the US. Consensus
was developed among the participants to create a draft
document titled “Mandate for Digital Earth Geobrowsers:
Status and Recommendations.”
2.4 US Developers Convene
A second workshop was hosted by the National Center for
Geographic Information and Analysis at Santa Barbara in
March 2003. A significant portion of the US Geobrowser
community was in attendance to further the development of
the draft document and to define criteria for the performance
goals likely to address the majority of the user community
requirements. Emphasis was placed upon alignment with the
ongoing protocols as well as the standards undergoing
definition from the ISO, OGC, and GSDI communities
(Foresman, et al, 2003). Many current developments in
Geobrowser implementation were created from the
partnerships formed at this workshop.
2.5 First Round Requirements
Initial goals for Geobrowser performance, or the functional
user requirements, were identified as a result of these two
workshops, Table 1. These results were considered, however,
to be both preliminary and high-altitude design guidance.
Further experience" with networked and semi-operations
systems would be required to fine tune the details of
architectural specifications useful to current and future
Geobrowser developers. These activities have been perused in
part by a strong desire to curtail the proliferation of stand-
along systems that end up detracting, not contributing, to the
improved cooperative understanding and management of the
Earth's resources.
Function or Description of Function or Element
Element
Platform/Server the hardware requirements for the server side
Hardware software operating in conjunction with
processors, memory, and other systems
components
Operating System | the operating systems that the software must run
on
the methods and algorithms applied to the
graphic presentation of three-dimensional
objects determining the performance and hence
functional limits
3-D Rendering
Tessellation the method used to enable dynamic, local to
global, seamless display of framework data
Client/Server the architectural strategy for hardware and
operating systems performance across à network
Data Type the capacity to handle different types of and
formatted data
Volumetric the methods and flexibility for addressing three-
Rendering dimensional displays and models for volumetric
applications
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