gis overview. what is gis? gis is an information system that allows for capture, storage, retrieval,...
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GIS Overview
What is GIS?
GIS is an information system that allows for capture, storage, retrieval, analysis and display of spatial data.
Characteristics of GIS?
GISGIS
Computer
Software
DataPeople ComputerHardware
People
People– Users
knowledgeable about geographic concepts and theory, GIS software, and data who can carry out the process
Data
Geographic data can include:– Remotely sensed data– GPS data– Census data– Road networks– Elevation data– Climate data– Power line coverage– Hydrography– Etc.
Data
Spatially Referenced– geographic data
contain information linking them to locations
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Data
Attributes – non-spatial characteristics of the features
linked to their geographic locations
Data in GIS (vector model)
Points(e.g., houses, cities)
Lines(e.g., roads)
Polygons(e.g., land parcels)
Data in GIS (raster model)
Data in GIS (raster model)
http://weather.unisys.com/surface/sst.gif
GIS Data TerminologyGeographic information / data can be referred to in all of the following ways (and more)– geographic data– spatial data – geospatial data– map data– GIS data– GIS layer– coverage– shapefile– locational data
From the Department of Redundancy Department
Computer Hardware
ComputersDigitizers and scannersPrinter and plotter output devicesDisk storage
Computer Software
Provides the ability to integrate, transform, analyze, and produce maps from geographic data to meet the needs of users
GIS In Practice: Project Design
GIS projects are developed to address a problem or answer a research questionIdeal Scenario:– Determine what output will best address the project
goal(s)– Determine the analyses that can best produce that output– Determine what data are needed for those analyses
Common Problems:– Analytical techniques may not be feasible due to
inadequate software functionality, user training, time constraints, etc.
– Data may be unavailable and too expensive to buy or collect
– Data may be impossible to collect (e.g., historic data)
GIS In Practice: Data Acquisition
Search GIS data available locally– Hard-drive, networked databases, CDs, DVDs, etc.
Convert non-GIS data– Scan air-photos or digitize paper maps
Search for free data online– Web searches of free data distribution sites
Ask other people for data and/or for how to find it– Ask other members of a research group, field of study, etc.– This can be tricky since data are expensive in terms of money and
time, can be sensitive/confidential, and may have great value to the person asked
Buy the data– Typically find it via web searches of sites selling data
Collect the data– Often expensive, slow, and difficult to do, and usually there are
strings attached like needing research permits or IRB approval
GIS In Practice: Data Issues
Storage– Decide where and how the data are going to be stored– Decide who will have access to these data– Decide how files will be named– Note: data storage is often given too little thought
initially and not addressed until problems arise later in the project
Metadata (data about the data)– Tells who created the data and how they did it– Ideally metadata will report the accuracy/quality of the
data – New datasets should all have metadata files created for
them
Simple Database ExampleOrange Co.
BaseData
DerivedData
Cities
Land Cover
Rates of Deforestation
UnprocessedProcessed
Satellite ImagesRoads
GIS In Practice: Preprocessing
Common preprocessing steps include– Converting all datasets to the same
projection– Clipping datasets to the same area– Changing the units (e.g., feet to
meters)– Rescaling the data to the same
resolution
GIS In Practice: Analysis
Use existing functionality in a GISExpanding the functionality of the GIS – Searching online for scripts that others have
developed– Writing your own scripts
Take advantage of functionality in other software– This can include other GIS packages– Using a remote sensing package to process satellite
imagery and using output from that in a GIS– Using statistical software to perform an analysis that
the GIS can not doMake your own software– This is what modelers do
GIS In Practice: Output
Making maps or tables that fulfill the project needs– Making nice maps takes time and a good
sense of designIncorporating the output into the larger project– Converting the maps to graphics for a report
or slides for a presentationInterpreting the results– Important and challenging– Note: making maps is often easier than
explaining what they mean
Quiz Time
Turn the quiz in on your way outSee you on Wednesday