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

Levels of geography Block group

Levels of geography ZIP code

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

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?

Where can we add new stores/Delis?

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 PARKS URBAN FOREST OVERLAY the layers on top of each other

Process the data SOILS PARKS URBAN Solution map FOREST Color in the unacceptable areas

Look at the results

Check out other similar projects

Map Overlay But what about the protected rats? SOILS PARKS URBAN Solution map FOREST Rats

Before GIS - Paper Computers speed the process Databases hold more information than paper Why GIS?  Faster  Cheaper  Easier  More