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

• 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

• 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?

• 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/ICPSR/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/workshops/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/