Geoscience Reference
In-Depth Information
4.5.1 d igital e arthS
In a speech, Gore (1998) stated '… we need a Digital Earth. A multi-resolution, three-dimensional
representation of the planet, into which we can embed vast quantities of geo-referenced data'. In
essence, Gore was calling for a virtual representation of the Earth on the Internet that is spatially
referenced and interconnected with digital databases from around the world. Indeed, just as we
discussed in Section 4.3, geography, especially location, provides a means to index and access such
information over the Internet, and in the concept of the Digital Earth, the rapid diffusion of geo-
browsers is simply in the vanguard of a whole series of software systems providing a geographically
enabled Web 2.0 service that promises to bring geolocation to the fore and of course to everyone
(Hudson-Smith, 2008).
The idea behind such a system is to allow users to navigate through space and time. Initially
while the idea of organising vast quantities of digital data to specific points was appealing, it was
not feasible due to hardware, software, networking and data interoperability limitations. However,
as Grossner et al. (2008) note, what made the Digital Earth concept possible was the Digital Earth
Initiative chaired by NASA which focused on infrastructure interoperability (once again stressing
the needs for standards for the GeoWeb). However, it was not until 2001 with the launch of Earth
Viewer by Keyhole* (later acquired by Google and becoming Google Earth) that the technical fea-
sibility of a Digital Earth viewer was possible on a desktop computer. A common feature of Digital
Earths (geo-browsers) is that they are built using a technology stack comprised of a thin client,
high-speed Internet connection and sophisticated server infrastructure (Craglia et al., 2008), and
such technologies were not available when Gore (1998) made his speech.
Google Earth (along with other geo-browsers) has increased awareness of GIS potential and
encourages researchers to explore more powerful techniques (Butler, 2006). 'Just as the PC democ-
ratised computing, so systems like Google Earth will democratise GIS' (Goodchild quoted in
Butler, 2006). The Google Earth phenomena have opened up some of the more straightforward
capabilities of GIS to the general public, making it easy to deploy geographical information across
computing platforms through a standard, easy-to-navigate GUI. They provide a base layer on which
to overlay data whereby users can pan (e.g. by dragging the mouse) and zoom (e.g. by using the
mouse wheel) on map data almost anywhere in the world. For example, in Figure 4.4, we show how
Google Earth can be used as a base layer to explore possible trajectories of the radioactive plume
from the Fukushima Daiichi nuclear disaster.
While geo-browsers are visually impressive, they are restricted to some sort of mashup capability
(as shown in Figure 4.4) or searching functionality and have limited spatial analysis functions (e.g.
positioning, measuring). More often than not they are used just for visualisation purposes. For
example, one can use Google Earth to explore how an area has changed as shown in Figure 4.5. But
such Digital Earths have been shown to build critical thinking and analysis and promote geographic
awareness (e.g. Patterson, 2007). This has lead some researchers, for example, Rau and Cheng
(2013), to call for a Web-based 3D GIS platform accessible over the Internet which is capable of 2D
and 3D spatial analysis. However, such systems are not widely available. For example, one has to
rely on specialised 3D GIS software to carry out visibility and viewshed with respect to building
heights (e.g. Yu et al., 2007) or emergency response (Kwan and Lee, 2005). If one wants to explore
changes over time or the linkage between human activity and the corresponding physical footprint
or vice versa (e.g. the potential impact of a hurricane on humans), one still has to turn to specific 3D
GIS. Nevertheless, it is important to realise the recent progress in Digital Earths which now provide
the capability to visualise past settlement patterns in three dimensions. For example, Digital Earths
have been used to reconstruct past settlements such as Chengtoushan in China (Sakamoto and
Chikatsu, 2002) to that of modern-day cities such as London, England (Hudson-Smith et al., 2005)
or a combination of both such as in Kyoto, Japan (Yano et al., 2009). Digital Earths can also be used
* Interestingly, one of the co-founders of Keyhole also developed technologies for Second Life (see Crampton, 2008).
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