Lecture 3

How does GIS work

How does GIS work?Maps are stored in computers

Databases and Tables

Geometry

Attributes

How does GIS work?Categories of reality are divided into layers

Countries, States, Cities

Parcels of land ownership

Roads, Rivers, Lakes, Buildings

ZIP codes

How does GIS work?Layers are made up of points, lines, or polygons

Cities – points

Roads – lines

Counties – polygons

Drawing maps Points, lines, polygons, and text

Main Street

Home

Work

Construction

Mall

Change street layer color and thickness

Main Street

Home

Work

Construction

Mall

Turn Streets layer off

Main Street

Home

Work

Construction

Mall

World country layer - polygons

Amelia Earhart’s last flight - lines

Cities (fuel stops) - points

Levels of geography Country State County City

DEMO

http://www.marshallco.org/www/maps/images/50seregexpl.jpg

Levels of geography Block group

http://www2.lib.udel.edu/subj/maps/internet/dedo/nnccinc.htm

Levels of geography ZIP code

http://cssr.berkeley.edu/cwscmsreports/maps/showEntriesCountymap.asp?page=Ora

Levels of geography Parcel Buildings Houses

GIS links attribute and spatial data Each layer has a database table Each map feature has one record in the table The table has attributes about the features

One to one: layer and table One to one: map feature and record

Is your data spatial? >80 percent of all data has location “What’s your ZIP code”

My customer database

Here is my store

ArcMap puts customers on the map

Before GIS Just Pens and Paper

http://www.census.gov/pubinfo/www/photos/img/lowres/Hist08l.jpg

GIS Power Just a database Tools Analysis GIS Science and Geography Geo Statistics Aids in decision making

Remember “Maps Communicate”

Which 8% of 7000 stores to close?

http://money.cnn.com/news/specials/storysupplement/starbucks_closings/CA.html

Where can we add new stores/Delis?

Where can we add new stores/Delis?

5 steps to GIS analysis

5 steps to GIS analysis Frame the question Get the data Choose analysis method Process the data Look at the results

Frame the question Where can we put a garbage dump?

Frame the question Where can we put a garbage dump?

Not on bad soil Out of the city Not in a park Not in a protected area like a forest More?

Get the data

SOILS

PARKS

URBAN

FOREST

Color in the unacceptable areas Can’t locate in dark areas

Choose analysis method

SOILS PARKSURBAN FOREST

OVERLAY the layers on top of each other

Process the data

SOILS

PARKS

URBAN

Solution mapFOREST

Color in the unacceptable areas

Look at the results

Check out other similar projects

http://www.ruralgis.org/conference/2004proceedings/thurs/session4/thurs_4_1_00.pdf

Map Overlay But what about the protected rats?

SOILS

PARKS

URBAN

Solution mapFOREST

Rats

Before GIS - Paper Computers speed the process Databases hold more information than paper Why GIS?

Faster Cheaper Easier More

http://www.census.gov/pubinfo/www/photos/img/lowres/Hist08l.jpg