GIS and other design issues and techniques
I. Geographic information systems
• What are they?
• Types of GIS
II. Using GIS
• A simple example
• Benefits of GIS
Introduction to Informatics - Fall 02
I. Geographic information systems
• What are they?
GIS is an application of information visualization
It allows layers of information to be combined to
increase our understandings of place
GIS is composed of computer software, hardware and
data, and personnel
Its purpose is to help manipulate, analyze and present
information that is tied to a spatial location
It is a method to visualize, manipulate, analyze, and
display spatial data
It links databases to maps to provide dynamic input
Introduction to Informatics - Fall 02
GIS mapping software links information about where
things are with information about what things are like
Like a paper map, a GIS map has
Points that represent features such as cities
Lines that represent features such as roads
Small areas that represent features such as lakes.
Unlike a paper map, this information comes from a
database and is displayed by user choice
It stores the point’s location, the length of the road, and
the size of the lake
The information in the map sits on a layer, and the users
turn on or off the layers according to their needs
Introduction to Informatics - Fall 02
• Types of GIS
Mapping where things are
This is what we tend to think of first
We look for a specific
object or a pattern
This is a map of
buildings and natural
features that are
potential hazards for
airplanes
http://www.gis.com/whatisgis/dowithgis.html
Introduction to Informatics - Fall 02
Mapping quantities
Some GIS applications add representations of numerical
value
This allows information
about quantity to be
linked to spatial data
This map shows the
amount of net traffic
across the major
backbones
http://www.cybergeography.org/atlas/cox_1457_large.jpg
Introduction to Informatics - Fall 02
Mapping density
In areas with many features it
is difficult to see which areas
have a higher concentration or
density
A density map measures the
number of features using a
uniform unit, such as acres or
square miles
This map shows instances of
excessive truancy
San Diego Police Department
San Diego, California
http://www.esri.com/mapmuseum/
Introduction to Informatics - Fall 02
Finding out what’s nearby
Use mapping to determine precise locations of residences
and business
This is good for
emergency planning
This map shows the
volume of emissions
of cars in Montana
It is used as data in
efforts to control
pollution
Introduction to Informatics - Fall 02
Mapping Change
Map the changes to anticipate future conditions, decide
on a course of action, or to evaluate the results of an
action or policy.
Map where and how things move over a period of time, to
gain insight into how they behave
Map change to anticipate future needs
A police chief might study how crime patterns change
from month to month to decide where officers should be
assigned
Map conditions before and after an action or event to see
the impact
Introduction to Informatics - Fall 02
This map shows
the path of
Hurricane Andrew
as it moved across
the Gulf of Mexico
on 8/24/92
The dots represent
maximum
windspeeds of the
hurricane over
times
Speeds range
from 35-50 MPH
(light blue) to 125-
150 MPH (red)
http://www.gis.com/whatisgis/change.html
Introduction to Informatics - Fall 02
GIS and other design issues and techniques
I. Geographic information systems
• What are they?
• Types of GIS
II. Using GIS
• A simple example
• Benefits of GIS
Introduction to Informatics - Fall 02
II. Using GIS
• A simple example
~Begin with a question
What can we tell about arson fires in the city?
Framing the question is important
The greater the specificity the better
It helps to determine the data, method, and analytic
tools
~Gather data
Data sources vary
They include databases in the organization, the net,
commercial providers, various government agencies
Introduction to Informatics - Fall 02
Data Types
GIS data comes in three basic forms
Spatial data: what maps are made of
These include points, lines, and areas and are basic to
GIS
It designates locations and shapes of map features such
as buildings, streets, or cities
Tabular data: adding information to maps
This information describes a map features
A map of customer locations is linked to demographic
information about those customers
Introduction to Informatics - Fall 02
Image data—using images to build maps
These include diverse elements suchas satellite
images, aerial photographs, and scanned data
These data are converted from paper to digital format
Data models:
Vector data model
Discrete features, such as customer locations and data
summarized by area, are represented using the vector
model
Raster data model
Continuous numeric values, such as elevation, and
continuous categories, such as vegetation types, are
represented using the raster model
Introduction to Informatics - Fall 02
How can a GIS use the information in a map?
Maps can be digitized with at mouse to collect the
coordinates of
features
Electronic
scanning
devices convert
map lines and
points to digits
http://www.usgs.gov/research/gis/work2.html
Introduction to Informatics - Fall 02
Spatial data Image data
Tabular data
http://www.gis.com/data/data_types.html
Introduction to Informatics - Fall 02
Questions to ask about data
What do you want to do with the data?
Do you want to do a certain type of analysis?
Do you simply want to draw an accurate street map?
Do you want to develop delivery routes?
What are the specific geographic features you need?
To gain the most from the GIS, determine the level of
detail required from the data.
What attributes of those features do you need?
Using streets, determine if none, some, or all of the
following are needed: street name, route number, road
surface class, address ranges, traffic volume…
Introduction to Informatics - Fall 02
What is the geographic extent of the area of interest?
Data can be acquired for areas as small as a ZIP Code or
as large as the entire world
What is the level of geography you want to examine within
your area of interest?
How current must the data be?
What type of computing environment will you be using?
What GIS software will you be using?
How many concurrent users will be accessing the data, at
how many locations?
Different scenarios will affect the type of data license
you buy
Introduction to Informatics - Fall 02
When do you need the data?
Orders requiring customization may take up to
several weeks to prepare and deliver
Will you need periodic data updates and, if so, how
frequently?
Are complete replacements of the data preferred or if
will transactional updates be sufficent?
Which of the data sets identified may be licensed from
the same data publisher?
There is no guarantee that data sets from different
publishers will overlay precisely
Feature identification attributes may not be the same
in different data sets
Introduction to Informatics - Fall 02
Budgetary constraints and proximity also play a role in
data acquisition
The data should be clean, accurate, and manageable
It will contain an explicit geographic reference
Latitude and longitude coordinates)
An implicit reference: address, postal code, census
tract name, road name
We’d like
Number and location of arson fires
Demographics of perpetrators
Location of elementary schools
Introduction to Informatics - Fall 02
~The analytic method involves the creation and
application of layers
Data layers must match up correctly to draw them on top
of each other or combine them to see relationships
They must use the same map projection and coordinate
system
Issues in choosing projections and coordinate systems:
Where the area is located that is being mapped
How large it is
If precise measurements of distance or area are needed
We’d like to overlay the layers with the information we’ve
requested
Introduction to Informatics - Fall 02
~Process the Data
To map where things are located, assign geographic
coordinates (latitude and longitude or address) to the
data
Assign category values to the data
To map quantities, such as number of vegetation types
in a state park, choose a classification scheme and
decide on the number of classes that represent the data
To find out what is inside, measure an area or combine
different layers of information
This is what we will do
Introduction to Informatics - Fall 02
Layer 1: Map of the
city
Layer 2: Location
of schools
Layer 3: Location
of fires School
Layer 4: Age of
arsonist
16-25
12-16
School
8-12
Introduction to Informatics - Fall 02
• Benefits of GIS
Improve organizational integration
GIS provides improved management of organizations and
resources
It links data sets using common spatial data, such as
addresses
This provides multiple points of access to shared data
It helps departments and agencies share data
Shared databases mean that data can be collected once
and used many times
One department can benefit from the work of another
Introduction to Informatics - Fall 02
Improve decision making
GIS is a tool to query, analyze, and map data to support
of decision making
For example, It can be used to reach decisions about
the location of a new land fill
The analysis points out areas that are low risk, have
minimal environmental impact, and are relatively far
from population centers
GIS information can be presented succinctly and clearly
in the form of maps and reports
Decision makers can focus on issues instead of data
Because GIS maps can be produced quickly, multiple
scenarios can be evaluated efficiently and effectively
Introduction to Informatics - Fall 02