virtual globes as "hubs" of knowledge and/or aggregators; Nasa World wind, marble, skylineglobe, google earth; Earth and coordinate systems;Digital Earth Reference Model;dynamic earth;some applications in geo-science, GIS

Digital Earth is a virtual representation of the Earth that is spatially referenced and "interconnected" with the web: http://www.digitalearth-isde.org/index.html
Geoweb is the spatialization of the Internet,  the merging of geographical (location-based) information. This would create an environment where one could search for things based on location instead of by keyword only – e.g. “What is Here?”. Geographic Information Retrieval is the "augmentation" of Information Retrieval with geographic metadata.


A) Earth and coordinate systems
A geographic coordinate system is just a coordinate system. This system enables every location on the Earth to be specified by a set of numbers. A common choice of coordinates is latitude, longitude (and elevation).
For reasons that are a mixture of valid science and historical "accident", there is no one agreed ‘latitude
and longitude’ coordinate system.
Exact formulae only apply in the realm of perfect geometry – not in the real world of coordinated points
on the ground...
http://reference.wolfram.com/mathematica/WorldPlot/tutorial/WorldPlotting.html
http://demonstrations.wolfram.com/topic.html?topic=Earth+Science&limit=20


Digital Earth Reference Model (DERM) : http://www.pyxisinnovation.com/pyxwiki/index.php?title=Digital_Earth_Reference_Model
The Digital Earth reference model seeks to facilitate the use of georeferenced information from multiple sources over the Internet.


DERM tends to encompasses 4 critical principals of a digital model namely:

• A discrete uniform partitioning also called a Geodesic Discrete Global Grid System (a tessellation or tiling of cells over the Earth surface). Criteria for an optimized discrete global grid has been proposed by Michael Goodchild - generally, equal area cells that exhaustively cover the globe in closely packed hierarchical tessellations, each cell representing a homogeneous value:
• A unique linear non floating point index for each discrete cell that encompasses within the index both a parent child hierarchical relationship and a coordinate system that converges uniformly to the set of all real numbers;
• A set of mathematical relationships and operations built on the index: algebra, geometry, Boolean operations, image processing, etc; and
• Drawing on signal processing theory, a strategy for quantizing values (preferable integers) from analog or other digital sources to each discrete cell.

You can download the latest version of WorldView™ GeoWeb Browser (6MB):
http://www.pyxisinnovation.com/downloads.php


B) Virtual globes (VG): 
comparison : http://en.wikipedia.org/wiki/Virtual_Globe
Created in 1999, the first software was 3D World Atlas (Cosmi Corporation)...


4 multi-platforms VG:

• *open source: Nasa World wind: http://goworldwind.org/
  (alexa rank 1500000 (DATA@august 2011)
  See this good wikipedia article: http://en.wikipedia.org/wiki/NASA_World_Wind;
  The size of all currently available data sets is 4.5 terabytes (from the NASA servers).
  It allows multiple datasets (google earth only one dataset)...
  World Wind can be expanded by using one of many add-ons and we can add new functionality to the program. Plugins are small programs written in C#, VB or J# which are loaded and compiled by World Wind at startup.
  download java SDK: http://worldwind.arc.nasa.gov/java/ and create your app: http://goworldwind.org/getting-started/
  see the demo: http://goworldwind.org/demos/
  World Wind Geo: The Eclipse RCP Geobrowser with the great java NetCDF library for plotting/subsetting capabilities of scientific data:
  http://code.google.com/p/worldwindrcp/
  
• *open source: http://edu.kde.org/marble/
  (alexa rank 14600 (DATA@august 2011) in fact rank of KDE)
  http://edu.kde.org/marble/download.php
  Marble is available in 2 flavours: The Marble-KDE and Marble-Qt
  
  
• *freeware: http://www.skylineglobe.com/SkylineGlobe/corporate/home/index.aspx?
  (alexa rank 1500000 (DATA@august 2011)
  online 3D globe website connected by API to TerraExplorer client app;10 terabytes imagery and elevation data collected from freely available satellite and aerial data.
  showcases: http://www.skylineglobe.com/SkylineGlobe/corporate/Industries/CustomerShowcase.aspx
  a) http://www.geoportail.fr/; http://193.48.79.17/territoires06/WebClient/PresentationLayer/WebClient/loginCG06.aspx; http://www.anru.fr/
  b) http://etat.geneve.ch/sitg/guichet-4254.html
  c) http://showtaiwan.hinet.net/
  d) http://www.adelaidecitycouncil.com/development/3d-city-model.html#
  
• *freeware: google earth: http://earth.google.com/. Google Earth can function as a "hub" of knowledge. The internal coordinate system of Google Earth is geographic coordinates (latitude/longitude) on the World Geodetic System of 1984 (WGS84) datum.
  http://googleenterprise.blogspot.com/2010/04/reinventing-classroom-geography-with.html
  kml/kmz add-on : http://www.google.com/gadgets/directory?synd=earth&cat=featured&preview=on
  agregator: http://www.google.com/submityourcontent/
  http://www.google.com/submityourcontent/tools.html
  http://www.google.com/submityourcontent/content_type/business_information.html
  http://earth.google.com/submit.html
  http://maps.google.com/support/bin/static.py?hl=en&topic=21676&guide=21670&page=guide.cs&from=21676&rd=2
  

C)Dynamic earth: relative to the centre of the Earth, a point on the ground can move as much as a metre up and down every day just because of the tidal influences of the sun and moon. The relative motion of two continents can be 10 cm a year...
some links:
http://www.ordnancesurvey.co.uk/oswebsite/gps/docs/A_Guide_to_Coordinate_Systems_in_Great_Britain.pdf
The result is that different systems of latitude and longitude in common use today can disagree on the coordinates of a point by more than 200 m.


Some scientific articles:
http://library.wolfram.com/infocenter/Articles/4551/


----list of ISDE (International Symposium on Digital Earth)
see the last keywords (program): http://www.isde7.net/program

Event	Year	Location	Theme
ISDE 1	1999	Beijing, China	Moving towards Digital Earth
ISDE 2	2001	New Brunswick, Canada	Beyond Information Infrastructure
ISDE 3	2003	Brno, Czech Republic	Information Resources for Global Sustainability
ISDE 4	2005	Tokyo, Japan	Digital Earth as a Global Commons
Digital Earth Summit '06	2006	Auckland, New Zealand	Information Resources for Global Sustainability
ISDE 5	2007	Berkeley & San Francisco, USA	Bringing Digital Earth down to Earth
Digital Earth Summit '08	2008	Potsdam, Germany	Geoinformatics: Tools for Global Change Research
ISDE 6	2009	Beijing, China	Digital Earth in Action
ISDE 7	2011	Perth, Western Australia	ISDE7 The Knowledge Generation