Finding the Mainstream - UCSB
Transcript of Finding the Mainstream - UCSB
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Finding the MainstreamFinding the Mainstream
Michael F. Goodchild
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GIS is becoming mainstreamGIS is becoming mainstream
More and more dependence on general IT solutions– RDBMS– Object models– CASE tools, UML
Location as an increasingly important attribute of records– in transactions– in location-based services
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Tract12345678
Pop
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3786Location
x,yx,yx,yx,yx,yx,yx,yx,y
Shape
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How special is GIS?How special is GIS?
It started as highly specialized– but has become less so over time– will GIS disappear into the IT mainstream?
What are the special characteristics of GIS?– is spatial special?– how special will GIS be in 20 years?
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Origins of GISOrigins of GIS
The Canada Geographic Information System– circa 1965 – support for the Canada Land Inventory– $20 million investment by the Government
of Canada– justified by accurate cost-benefit analysis
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Inventions attributable to CGISInventions attributable to CGIS
Measurement of area from digital mapsThe optical scannerThe Morton order– to minimize seek times for adjacent tiles
Topological data structures– to avoid double digitizing– a form of database normalization
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CGIS engineeringCGIS engineering
Low-level source code (PL1)IBM operating system (JCL)Custom input device (map scanner)
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A contemporary GISA contemporary GIS
RDBMSCASE tools for database design– Visio, UML
Graphics librariesReusable software componentsDynamic linking with other component libraries
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Mainstream database solutionsMainstream database solutions
The georelational model– adaptation of RDBMS– related tables– a hybrid of mainstream and specialized
Object-oriented modeling– objects as instances of general classes– classes as specializations of more general classes
(inheritance)– methods associated with classes (encapsulation)– associations between objects
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Specialized GIS data modelsSpecialized GIS data models
The basic elements built into the GIS– points, lines, areas– the GIS mainstream
How these elements are specialized in application domains (vertical markets)– railroad track as a class of transportation
link– transportation link as a class of line
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Unified Modeling LanguageUnified Modeling Language
Visual representation of a data model– conventional symbols– implemented in Visio
Creation of database layout– use CASE tools– build tables– populate tables with data
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UNETRANSUNETRANS
Helping transportation users of ArcGISby providing a database framework that includes familiar elements– contains the core items– is easy to extend and specialize– add new attributes– add specialized classes
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How important are coordinates anyway?How important are coordinates anyway?
Kocmoud and House, Texas A&M University
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Space as a matrixSpace as a matrix
W where wij is some measure of interaction– adjacency– decreasing function of distance– invariant under rotation, displacement– readily obtained from a GIS
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Lumpers and splittersLumpers and splitters
Lump GIS with other IT applications– and benefit from economies of scale– one RDBMS fits all
Split GIS from other IT applications– it addresses a unique type of information– it must adapt to the unique properties of
that type
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What’s special about spatial? A statistician’s viewWhat’s special about spatial? A statistician’s view
Spatial dependence– Tobler’s First Law of Geography– “All things are related, but nearby things are more
related than distant things”– properties vary slowly across the Earth’s surface– try to imagine a world in which that’s not true
• try to describe, navigate in, live in such a world• hell is a place with no spatial dependence
Spatial heterogeneity– results of analysis vary from one place to another
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What’s special about spatial? An SAP’s viewWhat’s special about spatial? An SAP’s view
Large volume– petabytes online
Uncertainty– impossible to measure location exactly– impossible to be certain about some attributes,
e.g. vegetation cover, soilApplications– in virtually all areas of human activity
Production arrangements– produced by central mapping agencies
Impacts on society– privacy
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What’s special about spatial? A database viewWhat’s special about spatial? A database view
First principle of OODB design– all objects are instances of more general classes
Not all geographic phenomena are easily conceptualized as discrete objects– road networks, topography are continuous– must be broken into discrete objects to be handled
in DBMS• but there are many possible ways of breaking them into
discrete chunks• dynamic segmentation
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A week in Jonathan Raper’s lifeA week in Jonathan Raper’s life
Colour= dayLight = early,dark = late
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Updating a street database through transactionsUpdating a street database through transactions
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If spatial is special...If spatial is special...
Special courses for SAPs– education in the principles of GIS– training in the practice of GIS
A distinct metadata standard– FGDC, ISO 19115, ANZLIC
Search engines– specialized to find geospatial data
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Conclusions (1)Conclusions (1)
Some GIS applications are more compatible with the IT mainstream than others
– discrete objects– location as an attribute– transactions
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Conclusions (2)Conclusions (2)
Other applications are much less compatible– GIS in scientific research
• dominance of fields of continuous variation• rasters vs discrete vector objects
– network applications• arbitrary chunking of networks
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Conclusions (3)Conclusions (3)
Economies of scale will continue to pull GIS into the mainstream– applications that are more specialized will
have to pull hard in the opposite directionGIS data sets require highly specialized tools for search and retrieval– a new generation of search engines is
badly needed
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Conclusions (4)Conclusions (4)
Because of the diversity of GIS, it will always be difficult to bound and regulate the field– except in limited, well-defined areas such as the
cadasterThe special characteristics of GIS will continue to foster– a science of geographic information– education in GIS at all levels– a need for training at all levels