Implementing Digital Earth: A Research Agenda Michael F. Goodchild University of California Santa Barbara

Perspectives on Digital Earth n 1. An immersive environment –“I believe 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.” U.S. Vice President Gore, 1/98 n Spin, zoom, pan –"fly-by" technology

Immersive environments n Head-mounted devices n Immersadesk n The "cave" n Standard computer displays –2D window on manipulable 3D objects –Nick Faust, Georgia Tech –SRI Digital Earth, Terravision –powerful processors, 3D graphics

Research challenges n Smooth zoom –10km to 1m resolution –consistent data structures < smooth transitions to more detailed data < color matches –projections < orthographic for the globe < projected for local detail < Georgia State: nested azimuthal projections

Research challenges (2) n Visualization –renderable data –non-renderable data < iconic representation indicating presence < symbolic representation –user-centered views < reduce resolution in periphery < avatar

Research challenges (3) n Local data, powerful processor –what is deliverable via the Internet? –bandwidth requirements –local data volume < cells at 1m resolution n Software environments –VRML, GeoVRML –Open GL –triangular data structures

Research challenges (4) n Discrete global grids –for indexing and data representation n QTM (Geoffrey Dutton, Spatial Effects) –8 triangles at level 0 –recursive subdivision into 4 triangles –address is 1 base 8 digit and n base 4 digits –level 20 is roughly 1m resolution

Discrete global grid based on the Icosahedron (20 triangles, 1:4 recursive subdivision) Ross Heikes and David Randall, Colorado State University

International Conference on Discrete Global Grids n Santa Barbara, California n March 26-28, 2000 n Abstracts due January 10, 2000 n

Perspectives on Digital Earth n 2. A metaphor for organizing information n The geolibrary –a library that is searchable by geographic location –"what have you got about there?" –physically impossible but feasible in a digital world

NRC report n "Distributed Geolibraries: Spatial Information Resources"

Organizing information by location n Information with a geographic footprint n Organizational metaphors –the desktop, office, workbench –the surface of the Earth

Research challenges n Defining footprints –fuzzy, vernacular n Mapping between georeferencing methods –the gazetteer n Search over a distributed archive –search engines –object-level metadata (OLM) –collection-level metadata (CLM)

CLM of the Alexandria Digital Library

Research challenges (2) n Approaches to CLM –by data type < ortho.mit.edu –by area of the globe < SRI's Digital Earth, IBM's WorldBoard –the one stop shop < –a new generation of search engines < identifying footprints

Perspectives on Digital Earth n 3. The Mother of All Databases (MOADB) n A distributed collection of knowledge about the Earth –transparent to the user –accessible through geolibrary mechanisms –supported by consistent protocols

Perspectives on Digital Earth n 4. A collection of knowledge about the Earth's dynamics –the processes that create and modify the landscape n Dynamics or statics? –most GIS data are cross-sectional time- slices < providing facts –understanding of the Earth must focus on processes

Bernhardus Varenius n n General geography –the principles, processes n Special geography –the unique properties of places –the boundary conditions

A dynamic Digital Earth n Simulations of past and future conditions n A library of simulation models –applied to local conditions represented by data n A tool with enormous educational value n PCRaster demonstrations –University of Utrecht, Peter Burrough

Three probabilities for dispersion 1 Probability of individual reaching a given distance from the parent 2 Probability that habitat permits individual to establish 3 Probability that individual produces new offspring UCEL

Simple dispersion functions Probability of establishment UCEL

Example of diffusion modelling n Dispersion of individuals over a space in which the resistance to movement is variable, individuals need to work together to colonize new areas diffusion

Modelling uplift in Sabah, Malaysia. UCEL

Over a period of several million years movement along the faults has created long sediment-filled valleys UCEL Faults Relative vertical displacement Sediment

The demo illustrates: n A simplified model of normal faults and landform before uplift n Reaction of landform to gradual vertical displacement along the parallel normal faults n Erosion and deposition as a result of vertical movements (red is erosion - blue is deposition) n Emergent behaviour of rivers leading to development of braided streams tectonics

Research challenges n Data structures and modeling –no finite difference models on the curved surface of the planet –finite element models based on triangles? –object-based models n Describing models –metadata –libraries of models

Research challenges (2) n Software environments –PCRaster n Calibration, verification, accuracy n Integration across domains –coupling models –distinct ontologies

Summary: four perspectives n An immersive environment n A metaphor for information organization n A distributed database transparent to the user n A representation of the planet's dynamics

Augmented reality n Information tied to location –accessible by a person at that location –locationally enabled devices < palmtop with GPS < cellphone n Delivering DE services in the field –wireless devices –g-commerce

Digital Earth: a mirror world n Models of the Earth –maps –descriptive text –process models n Collectively, a storehouse of knowledge about the planet –distributed –digital –captures our understanding of the world