GIS Maps: Basic Terminology
University of Illinois Library
Eric Johnson - 2012
Goals for today
• Learn some GIS terms
• Learn how to find data and shape files
• Make some maps
Introductions
• Name
• Department
• A sentence about why you are here
GIS terms
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•
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•
•
Thematic map
Choropleth
Latitude & Longitude
Projection
Layer
Shape file
Base map
Thematic Map
• A map with a theme
• Usually shows landmarks so you know
where you are looking
• Start with a base map, then add points,
symbols, and shapes to display a concept
• This will probably be the type of map you
are interested in making
Choropleth
• Each area is colored to indicate information
Symbol = information
Location = geographic relationship
http://pokemonrusset.com/Info/Locations
What is this?
• A volcano
• ice cream with flavor
chunks
• Meteorite crater
• Lunar surface
• Mt. Kilimanjaro
• Polar ice cap
• child’s art project
Same location showing altitude
instead of geologic formations
• A volcano
• ice cream with flavor
chunks
• Meteorite crater
• Lunar surface
• Mt. Kilimanjaro
• Polar ice cap
• Son’s art project
Lunar Reconnaissance Orbiter using
the Lunar Orbiter Laser Altimeter
Latitude & Longitude
Latitude & Longitude
• A coordinate system used to locate
any surface point on a globe.
• Rotates with the globe.
(not sun based)
• With the addition of altitude, any
point on, in or near a planet can be
located.
Latitude & Longitude
http://www.flickr.com/photos/smithsonian/2940640045/
Latitude & Longitude
• Latitude = “parallels”
• Are parallel on a globe
• Measure North and South
• Longitude = “meridians”
• Long lines go North and South
• Measure East and West.
Prime Meridian
• Zero point for
measuring
longitude
• Passes
through the
Royal
Observatory
in London
http://en.wikipedia.org/wiki/File:Greenwich_observatory_laser.jpg
Projections
• The sphere often needs to be
converted to a flat image.
• Imagine a light bulb inside the globe
and continent’s shadows projected
on the wall.
• All projections distort the sphere.
Equal Area, U.S.
• Attempts
to keep
areas
correct
• Shapes
and
directions
will be
warped
Use the projection made for your
region
NAD 1983- State Plane Colorado
We can make all latitudes straight
But, it stretches Canada and shrinks Texas
4 types of Layers
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Point (locations of cities)
Line (roads and rivers)
Polygon (shapes of states and counties)
Images (like background terrain)
Layers can be combined many ways
Roads + Terrain Layers
Planning your own map
• Data
• Shape files (to visually hold the data)
• Base map (the background geography)
Data: What information do you
want to analyze or display?
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What is your question or problem?
Define what you want to visualize.
What point do you want to make?
What types of data did you collect?
People, things, activities
• When is the data? What time period(s)?
Shape files: The map outlines
of the data
• If the data is about states, then you need
the shape of each of state.
• Choropleth (“many areas”) maps fill each
shape with a different color to indicate
information.
• Shape files are also called “Polygon files”
Base map: an informative
background for the data
• Helps the user know where the data is
located.
• Gives other useful information such as
terrain, roads and place names.
Data sources
• http://www.library.illinois.edu/datagis/
lists many excellent resources
• http://www.icpsr.umich.edu/icpsrweb/IC
PSR/access/index.jsp (ICPSR) for social
science data
• http://factfinder2.census.gov for U. S.
census data
Historic data sources
• https://www.nhgis.org/ National
Historical Geographic Information
System
• Collection of census data and shape files
both current and historic
US Census data
• Census data: American FactFinder
http://factfinder2.census.gov/faces/nav/
jsf/pages/index.xhtml
• Alternative portal to census data:
DataFerrett http://dataferrett.census.gov
Other workshops in this series
• Library GIS 101 – An introduction to some of
the ways people are using GIS. Examples of
maps and GIS tools in action.
• Library GIS 103 – ArcGIS: Importing images
and giving them locations, creating shape
files, shading areas of proximity
Survey
• What GIS skills would you like to learn?
For more help…
• Scholarly Commons for one-on-one
consultation.
http://www.library.illinois.edu/sc/
• ATLAS data services and GIS training
http://www.atlas.illinois.edu/services/stats/w
orkshops/registration/
• ArcGIS classes at U. of I.: ESE 379, GEOG 105,
GEOG 379, LIS 490GIG, LIS 490GIL(online),
NRES 454, UP 418, UP 519
• Links to numeric and spatial data
http://www.library.illinois.edu/datagis/