Defining Digital Earth as a virtual representation of all digital information with a geospatial component, this geography attempts to delineate the scope and elements of Digital Earth. The framework for this geography is a set of layers applicable to describing an information system. From bottom to top the layers are physical, data, information, knowledge, decisions and actions. Conclusions of this geography are that some technologies are sufficient for a Digital Earth to come into existence, but some technologies, in particular in the upper layers, need to be developed. Three conclusions are listed in this abstract. In the physical and data layers, the explosive growth of Internet provides access to much Digital Earth data. However, the bandwidth necessary for high-end Digital Earth clients will not be widely deployed for some time. In the near term it will be necessary to have Digital Earth access points in public places like museums where high bandwidth is available. Digital Earth information volume is estimated by assuming a fraction of all digital information that has a geospatial component. Estimates place the total volume of recorded information at several thousand petabytes, i.e., several exabytes. It has been regularly postulated in the geographic community that half or more of all information has a geospatial component. Even though we will soon have the capacity to digitally record this volume of information, most of of it will never be looked at by a human. Tools are needed for auto-summarization, distilling the information into knowledge with lower volume and higher semantic content. To allow decisions and actions based on the knowledge of Digital Earth requires analysis of the knowledge using tools particular to the geospatial domain. As Digital Earth will exist in a distributed service environment based on standards for interoperability, the standards must address the particulars of geospatial semantics. Syntax standards for transporting semantic information (e.g., XML) have been defined and extended with geospatial structures. Standards for achieving shared understandings ("domain semantics") are yet to be developed. Beyond domain semantics, the validity of chaining services on geospatial features ("process semantics") is less developed.

1. A Geography Of
Digital Earth
George Percivall
Digital Earth Office
percivall@gsfc.nasa.gov

2. 14-Nov-01 p1
Digital Earth
•A virtual representation of our planet that
enables a person to explore and interact
with the vast amounts of natural and
cultural information gathered about the
Earth
–multi-resolution
–three-dimensional representation
•Surface of the earth as the organizing
metaphor for a vast amount of data

3. 14-Nov-01 p2
Public
Tools &
Technology
Tools &
Technology
Enabling Citizens
and Communities
Enabling Citizens
and Communities
Interoperability
Interoperability
Collecting Data
Collecting Data
EARTH
EARTH
P
r
i
v
a
t
e
Digital Earth
Digital Resources
Digital Resources
Applications
Applications

4. 14-Nov-01 p3
Decisions
Knowledge
Information
Data
Adapted from “A Theory of Computer Semiotics”, Peter Andersen, Cambridge Press, 1997
Definitions from ANSI Dictionary of Information Technology, www.ncits.org
A Geography for Digital Earth
Compression of redundancies
Representation is described
Data with meaning assigned
Integrated model of information
Pragmatic application of knowledge
Goals of multiple stakeholders
A representation subject to interpretation

5. 14-Nov-01 p4
A Geography for Digital Earth
Decisions
Knowledge
Information
Data
Decision Support
Phenomena Location
Vladimir and Estragon
Models, Agents,
and Knowledge
Fusion and
Assimilation
Content is King? Where in DE are you?
How big is DE? The world is wired

6. 14-Nov-01 p5
The World is Wired and Wireless
• Internet is Pervasive
–IPV6 - nearly 1,600 addresses/sq-m of the earth
~ 1 per sq inch
• Gilder’s law: Deployed bandwidth triples every year
• Wired bandwidth
–Gigabit Ethernet now, Terabit Ethernet in 2008
–Landsat scene transfer: 1 per sec now, 1000 per sec in 2008
• Wireless bandwidth
–4th generation Wireless: 10 to 100 megabit/second (2010)
–Full motion video on wireless devices
• Deployment will take time
–Necessary for Digital Earth access points in public places like
museums
Decisions
Knowledge
Information
Data

7. 14-Nov-01 p6
The Digital Earth — Varying Scales
e.g.
Land Use
Demographics
Global Climate
Sea Surface Temperature
Digital Elevation
HUMANITY
HUMANITY
e.g.
Food and Fiber
Disaster Preparedness
Biodiversity
Coastal Sensitivity
COUNTRY
COUNTRY
e.g.
Smart Growth
Public Health
Disaster Response
Transportation Planning
Weather
COMMUNITY
COMMUNITY
e.g.
Education
Decision Making
Enhanced Living
Information
INDIVIDUAL
INDIVIDUAL
Vision
Initiative
NASA Program
Decisions
Knowledge
Information
Data

8. 14-Nov-01 p7
• All recorded information:
~ several exabytes
• Most data has geographic
component
• DE ~ an exabyte
Yotta
Zetta
Exa
Peta
Tera
Giga
Mega
Kilo
How big is DE?
A Book
A Book
.Movie
All LoC books
(words) 20 TB
All Books
MultiMedia
Everything!
Recorded
A Photo
A Photo
Data
Archive
NASA
EOSDIS
Digital
Earth
Map
Satellite
Image
www.lesk.com/mlesk/ksg97/ksg.html
• Archive organization
–Image products in collections
–CEOS Census: millions of collections
–On-line collections: 10’s of thousands
–Collections cataloged
• Need to get data on-line

9. 14-Nov-01 p8
Decisions
Knowledge
Information
Data
Moving Digital Earth online
• Progression of Storage Technology
–Disk technology is overtaking tapes
–EOSDIS data moving from tape to disk
–In ten years RAM will cost what disk costs today
• Hurdles to moving online: technical, legal, business
–Technical issues of accessibility - geocoding,
geographic access standards
–“Government commercialization” concerns
–Owners fear intellectual property will be stolen.
–Need for copy-protection & payment schemes
–Privacy Impact Assessment
“Rules of Thumb in Data Engineering,” March 2000, Microsoft Technical Report, MS-TR-99-100
“Data Policy Issues and Barriers to Using Commercial Resources” Rand Doc No: DB-247-NASA/OSTP, 1999

10. 14-Nov-01 p9
Decisions
Knowledge
Information
Data
Finding value in DE Data
• Technology will allow us to store every thing
–In only a few years, we will be able save everything,
no information will have to be thrown out
–Human attention is the scarce resource
–Most of this data will never be looked at by a human being
• Domain Semantics
–Needs to have representation with the data, I.e. information
–Geography Markup Language
–Information communities, semantic nets, RDF
• Enables auto-summarization
–Mining based on geographic concepts
–Feature Tracking
–Feature Classification - Feature Type Catalogs
ADaM data mining engine, http://datamining.itsc.uah.edu/environment.html

11. 14-Nov-01 p10
Decisions
Knowledge
Information
Data
Is Content King in Digital Earth?
• Economics of a telecommunications medium
–“Content is King” vs. “Commodity Pipelines”
–Broadcast content is most of the data volume
–Point to point communications is most of the dollars
• Content is King in DE
–Professionally developed content from data centers
• Commodity Pipelines prevails in DE
–Individuals providing information from a geographic location
• Need for geographic device directory, e.g., dot-geo
• cellular Cams, GPS and Virtualized Reality (CMU)
–Sensor webs
• The need for geographic reference
“The history of communications and its implications for the Internet,” Odlyzko, AT&T Labs

12. 14-Nov-01 p11
• Coordinate Reference Systems
–Mature technology including ISO standards
–Registries for specific coordinate reference systems
• Overlay of multi-site 2-D data
–Standardized using OGC Web Mapping Service (WMS)
– “Digital Earth will do for georeferenced information what the
World Wide Web did for text and multimedia” - Jeff de La
Beaujardiere
Knowing where you are in DE
Decisions
Knowledge
Information
Data
• Merging multi-site 3-D and 4-D data
–Demonstrated as research
–Standards needed

13. 14-Nov-01 p12
Knowing where you are in DE
Decisions
Knowledge
Information
Data
Space Time Toolkit: http://vast.uah.edu/
• Merging multi-site 3-D and 4-D data
–Demonstrated as research
–Standards needed

14. 14-Nov-01 p13
Decisions
Knowledge
Information
Data
Fusion and Assimilation
• Data Fusion
–combine remote sensing data with other sources of geospatial
information to improve the understanding of specific
phenomena.
–Fusion Levels: Pixel, Features, Decisions
• Data Assimilation
–melding observations with model simulations to provide
accurate estimation of the state of the atmosphere, oceans,
and land-surface, etc.
• Models
–Simulations of a given topic
–Geographic models utilize coordinate reference systems
–Metadata for models to enable interoperability

15. 14-Nov-01 p14
Decisions
Knowledge
Information
Data
Models, Agents, and Knowledge
• Agents
–Software that runs without direct human control to accomplish
goals provided by a user
–Agents collect, filter and process information found on the
Web, sometimes with the help of other agents.
• Process Semantics
–Define automated interaction of Agents and Models
–W3C activity - Semantic Web:
• Use rules to make inferences, choose courses of action and
answer questions
–Digital Earth is a Geographic Semantic Web
• Geospatial linkages are well understood semantics
• Needed technology
–Geographic Ontologies
–Software interoperability stack

16. 14-Nov-01 p15
Decisions
Knowledge
Information
Data
Catalog
Catalog
Catalogs Geoprocessing
Services
Features
Other
Content Repositories
Coverages
D i r e c t
data
access
Pictures / maps /
Transformed data
Metadata Update
M e t a d a t a s e a r c h
a n d r e t r i e v a l
User
Applications
Middleware
Agents
Servers
And Models
S e r v i c e C h a i n i n g
Interoperability Stack
Digital Earth Reference Model

17. 14-Nov-01 p16
Decisions
Knowledge
Information
Data
Decision Support Systems
``Interactive system to help decision makers
select options”
–Large quantities of space-time data
–Models for predicting results of alternative policy choices
–Display the results in easily understood ways to multiple
communities
• Technology Progression
–Many models and DSS environments exist in close solutions
–Need for distributed DSS, scripting, workflow
• DE supports multiple decision making methods
–Content is King - professional data bases, models, and
decision processes
–Simple Pipes - point to point communications about the state of
the earth will enable inform the democratic decision process

18. 14-Nov-01 p17
A Geography for Digital Earth
Decisions
Knowledge
Information
Data
Decision Support
Phenomena Place
Vladimir and Estragon
Models, Agents,
and Knowledge
Fusion and
Assimilation
Content is King?
Where in DE are
you?
How big is DE? The world is wired

19. 14-Nov-01 p18
Waiting for Godot,
by Samuel Beckett
Vladimir: Well? Shall we go?
Estragon: Yes, let’s go
They do not move
Curtain
Decisions
Knowledge
Information
Data
Final Scene: Two men along a country road

20. 14-Nov-01 p19
Waiting for Godot,
in Digital Earth
Final Scene: Two men along a country road
Vladimir: Well? Shall we go?
Estragon: Yes, let’s go
They depart
Curtain
Decisions
Knowledge
Information
Data

21. 14-Nov-01 p20
Questions?
Questions?