## Tuesday, August 30, 2011

### 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.

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:
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...
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

EventYearLocationTheme
ISDE 11999Beijing, ChinaMoving towards Digital Earth
ISDE 22001New Brunswick, CanadaBeyond Information Infrastructure
ISDE 32003Brno, Czech RepublicInformation Resources for Global Sustainability
ISDE 42005Tokyo, JapanDigital Earth as a Global Commons
Digital Earth Summit '062006Auckland, New ZealandInformation Resources for Global Sustainability
ISDE 52007Berkeley & San Francisco, USABringing Digital Earth down to Earth
Digital Earth Summit '082008Potsdam, GermanyGeoinformatics: Tools for Global Change Research
ISDE 62009Beijing, ChinaDigital Earth in Action
ISDE 72011Perth, Western AustraliaISDE7 The Knowledge Generation