Introduction to Geographic Information

Introduction to Geographic Information

Fall 2006

Instructor: Christine Erlien

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Overview What is geography? What is geographic information?

How do we get it? What do we do with it?

What is a GIS? Difference from CAC, CAD, analog mapping

GIS applications Tool versus science

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Geography = Place names only?

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What is geography? The scientific study of the locational and spatial

variation in physical and human phenomena Where things are located on the earth’s surface

Why things are located where they are

How places differ from one another

How people interact with the environment

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Geographic Information Examining patterns & processes of human and

physical phenomena on the surface of earth

Examples of geographic information: Spatial distribution of world population totals or

growth rates Location of Chapel Hill Interstate I40’s spatial pattern Urban sprawl/development of Raleigh over time

http://sedac.ciesin.columbia.edu/gpw/

World Vegetation

http://www.miamisci.org/ecolinks/mapbiosphere.html

http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/Maps/map_plate_tectonics_world.html

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Geographic Information (GI)

GI - static or dynamic? Static: Does not change position

Benchmarks Locations, such as city/town, lake, park

Dynamic Car with On-Star recording its position Cell-phones used to track children’s locations Studying population change at a particular location

over time

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How do we obtain geographic information? Aerial photographs Digital remote sensing Surveying Censuses Global Positioning System Digitizing maps

11Aerial photograph from http://terraserver.microsoft.com

NC Satellite Image

www.geology.com

Surveying: benchmarks

Geodetic control points

Mark a point of known vertical elevation

Height calculated from height of nearby benchmarks

GPS receivers

Digitizing

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We’ve collected GI, now what do we do with it? Analyze the data

Make maps to present the data to others

How? By using a GIS

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GIS: Geographic Information Systems GIS is built on collective knowledge

Geography Cartography Computer science Mathematics

Many definitions, depending on whom you ask Demers (our textbook) cites Marble & Pequet

(1983), who talk about what we do with a GIS and how we do it 

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Data: Both spatial and temporalSpatial: Related to the space around usTemporal: Related to time

The what and how of GIS:Data input subsystem: Collecting & preprocessing dataData storage & retrieval subsystem: Retrieval, updating, editingData manipulation & analysis subsystem: Analysis & modelingReporting subsystem: Display

What this boils down to: “GIS is an information system that allows for capture, storage, retrieval, analysis and display of spatial data.”

Marble and Pequet (1983)

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GIS

An information system that allows for Capture Storage Retrieval Analysis Display

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Computer hardware Software

Data management and analysis procedures

Spatial data People needed to operate the GIS

Components of a GIS

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The rise of GIS Canada, early 1960s, Dr. Roger Tomlinson Need: inventory & map natural resources A huge task, aided by advances in computing

technology Computers: vacuum tubes transistors

Faster, more reliable, cheaper Larger memories information storage as well as

calculations possible Mainframe used had 512K of memory!!!!

IBM develops the drum scanner to scan lines on maps –1st in the world

Interested in more history? Seehttp://www.casa.ucl.ac.uk/gistimeline/ for an interactive timeline

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How does GIS differ from CAC and CAD? Computer-aided cartography (CAC):

Primarily used in map-making (display) Examples

Global Mapper MapMaker ArcExplorer

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How does GIS differ from CAC and CAD? Computer-aided drafting (CAD)

Used by architects to produce graphic images (display)

Images not linked to descriptive files

What key capability of GIS is lacking in both CAC and CAD?

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Comparing traditional cartography & GIS: InputsTraditional Data sources

Aerial photography Digital remote sensing Survey Census & statistical

data Data recorded as

points, lines, areas on paper or Mylar

GIS Data sources

Same, plus DLGs DEMs Digital orthophotoquads

Data recorded as points, lines, areas using electronic devices

DLGs

Layer Feature Type

Public Land Survey System (PLSS) Township, range, and section lines

BoundariesState, county, city, and other national and

State lands such as forests and parks

TransportationRoads and trails, railroads, pipelines and

transmission lines

Hydrography Flowing water, standing water, and wetlands

DEMs

Digital elevation models

Usually 30 m resolution

Used to determine terrain attributes (slope aspect)

http://www.ngs.noaa.gov/RESEARCH/RSD/main/yakutat/yakori_full.html

DOQs Digital rep. of aerial

photographs Corrected for

image distortions Stored digitally

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Comparing traditional cartography & GIS: Storage & RetrievalTraditional Storage: points,

lines, areas drawn on map

Retrieval: Map reading

GIS Storage:

Points, lines, areas stored with spatial reference data (coordinates) & pointers

Tables of characteristics (attributes) associated with coordinates

Retrieval: Computer tracks where data are stored

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Comparing traditional cartography & GIS: Analysis & Output

Traditional Analysis: Limited to

data as presented on map

Output: Mapping

GIS Analysis: Allows

access to raw data can change aggregation or classification, or analyse further

Output: May include maps, tables, charts

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GIS Application Areas Government

Census Bureau: population Dept of Agriculture: soils data Dept of Defense/CIA: monitoring Dept of Transportation: roads data Political redistricting

Business Researching retail markets Evaluating site suitability Evaluating health care resources

Education & Research Land use change research Environmental monitoring Seismological research Population research

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Reasons for GIS applications Information Management

Data input Data editing Updating

Data output and display Maps Spatial information queries Time series of maps (tracking storms,

population growth, etc.)

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Reasons for GIS applications (Cont.)

Spatial Analysis Shortest Distance Buffer analysis Classification

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The Role of GIS within Geography GIS is an effective tool that integrates human

and physical geography GIS can combine (and overlay) human and

physical data Tool v.s. science

GIS is a tool for those who use it to conduct research on other subjects

GISci: Study of the fundamental issues arising from the creation, handling, storage, and use of geographic information

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To wrap up

What is geographic information? How do we get it? What do we do with it?

What is a GIS? Difference from CAC, CAD, analog

mapping GIS applications Tool versus science