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