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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B6. Istanbul 2004
limits. À general database of educational material is provided
by the "Gateway to Educational Materials" project
(http:/www.thegateway.org), a consortium effort created to
provide easy access to the substantial, but uncataloged,
collections of educational materials available on various federal,
state, university, non-profit, and commercial Internet sites.
Another Internet portal full of resources of relevance to
faculties, students, and research staff at the university level is
Infomine (http://infomine.uer.edu/). It is a huge database
including electronic journals, electronic books, bulletin boards,
listservs, online library card catalogues, articles and directories
of researchers and many other types of information. More
specific resources in Remote Sensing, just to mention few good
links, are provided by NASA (http://rst.gsfc.nasa.gov), ASPRS
(http://research.umbc.edu/~tbenjal), CCRS
(http://Www.cers.nrcan.gc.ca/cers/learn/learn_e.html) and
CEOS CD-ROM (http://ceos.cnes.fr:8100/).
Concerning articles, publications and presentations available on
the net, they can be easily found using a powerful search engine
or through Citeseer (http://citeseer.ist.psu.edu/), a scientific
digital library.
2.11 E-Learning
E-learning is the education via Internet, network or standalone
computer. E-learning uses electronic applications and processes
to teach and learn as the network enables easily transfer of
skills and knowledge between users. E-learning applications
and processes include Web-based learning, computer-based
learning, virtual classrooms and digital collaboration. Content
is delivered via the Internet, intranet/extranet, audio or video
tape, satellite TV and CD-ROM.
An e-learning web sites collection is provided by the University
of Leicester (http://Www.le.ac.uk/ce/rjm1/isp/ele.html).
2.12 Internet growth and its statistics
It is very difficult to determine how many users and how many
domains or hosts are on the net, besides making guesses and
estimates. There are many companies that do surveys to
estimate the number of users, but we can consider the numbers
presented in these surveys to be fairly good estimates of the
minimum size of the Internet. And often the results are also in
disagreement. Moreover the geographical location of an
Internet host is somewhat problematic since a host need not to
be located in the country which correspond to its ccTLD; and
gTLD has never an explicit geographic designation (e.g. ISPRS,
with the server in Zurich, the Headquarter in London and the
President in Sidney!) For these reasons is not possible to
determine the exact size of the Internet, where host are located
or how many users there are.
The growth of the available information can be estimated from
the number of registered host (e.g., a computer or machine with
a unique IP address on a network). According to the Internet
Software Consortium [ISC, 2004], the number of registered
hosts states 80,000 in January 1988, 1.3 million in January
1993, 16.1 million in January 1997 and 109.7 million in
January 2001 (Figure 10). Internet hosts include network
elements such as routers, Web servers, mail servers,
workstations in universities and businesses, and ports in modem
banks of Internet Service Providers (ISPs). The number of hosts
is considered one of the most accurate measures of the size of
the Internet, even if their distribution is concentrated mainly in
the most delevopded countries (Figure 11).
In 1997, the OCLC Office of Research started a project aimed
at answering fundamental questions about the Web, like how
117
big is it? what does it contain? how is it evolving? The project's
objective was to develop and implement a methodology for
Number of users online
Million of users online
io © P= o = e e
c» e» e c» e © c m =
© © e e e e c e ©
joue S T T e e 2 ex
Years
Figure 10: Internet growth represented by the number of
Internet hosts. Source: [ISC, NUA].
characterizing the size, structure, and content of the Web,
making the results available to both the library community and
the public at large. The strategy adopted for characterizing the
Web was to harvest a representative sample of web sites, and
use this sample as the basis for compute an estimate and make
an inference about the Web [O'Neill et al., 1997]. According to
OCLC, the web sites can be divided in three categories: (1)
public, sites that provide free and unrestricted access to all or at
least a significant portion of its content; (2) private, sites whose
content is intended for a restricted audience; the restriction can
be explicit (e.g., fee payment or authorisation) or implicit
(obvious from nature of content); (3) provisional, sites in
transitory or unfinished state (e.g., "under construction"),
and/or offers content that is, from a general perspective,
meaningless or trivial. In the most recent survey (2002) of the
OCLC Web Characterization Project [OCLC, 2004], the web
contains 9.04 millions of web sites (with 8.7 millions of unique
web sites, i.e., the count is adjusted to account for sites
duplicated at multiple IP addresses). The growth of unique web
site between 1998 and 2002 is ca 231%. OCLC found that
15.5% of the web sites provides information services, 14.2%
provides professional, scientific and technical services, 11.8
retail trade and 6.6% provides educational services.
Internet hosts distribution
AFRICA
0.1535 7
T EUROPA
E. % _ MIDDLE EAST
uu 0.14%
USA & CANADA
75 08%
.. LATIN AMERICA
pu 2.70%
|
PACIFIC
1.93%
Figure 11: Distribution of Internet hosts. Source [ITU].
Considering the million of users online (Figure 12), the number
of people is constantly increasing. In 1995 the Internet
population was only 16 million people (app. 0.35% of the world
population) while at the middle of 2003 there were more than
730 million people online (11.596 of world population) [NUA ].
The number is expected to increase again in the next years and
a CIA (Computer Industry Almanac) document reports that in
