An Introduction to Geographic
Information Systems (GIS)
Presented March 14, 2007
Explain what a geographic information system
Provide a history of GIS.
Describe different types of data elements.
Explain spatial scales.
Provide an overview of the map elements.
Introduce 4 different types of maps.
“GIS is a collection of computer hardware, software, and
geographic data for capturing, managing, analyzing, and
displaying all forms of geographically referenced
What is a GIS
Acronym for Geographic Information Systems.
In a GIS, we combine geographic locations with
descriptive data about the locations.
Database and map are linked to allow us to
Visualize the results on a map
The goal is to help us gain a better
understanding of our world so we can enhance
planning and decision making.
History of GIS
1854 Dr. John Snow created a map to show the locations of
death by cholera in central London. This technique was
used to track the source to a contaminated well.
1960s Roger Tomlinson helped to design and develop the
Canadian GIS (CGIS). The CGIS was used to manage and
analyze Canada Land Inventory Data monitor and the
1960s SYMAP the 1st mapping package developed by
Increased access to data and technological advances such
as having smaller more powerful computers with greater
storage capacity has helped the field to develop rapidly.
Components of a GIS
Geographical locations (spatial data)
Information about the locations (attributes or
Software for storing and managing the data.
Computers to facilitate the data storage,
processing and analysis.
People to operate the GIS
Attribute Data Location Data
What is it? Where is it?
• road • XY Coordinate data
How can we describe it? (latitude and longitude)
• Length of road segment
• Date of construction
Spatial data contain the
coordinates and identifying
information that is necessary
to draw maps.
A layer is a collection of all
the features in the map that
share some common
Three types of layers can be
represented in a GIS: points,
lines, and areas
When the various layers are
overlaid, they form a map
5 Functions of a GIS
Manipulation and analysis
Generation of maps, images, reports and tables.
7 Types of Questions a GIS Can Answer
Can you map that?
Where is that?
What has changed?
What relationships exist?
Where is it best?
What afffects what?
Source: Joseph K. Berry (1995) Spatial Reasoning for Effective Reasoning. GIS World Books.
Representing Map Features
Representation of real-world objects
on a map using symbols and their
locations and geometry with:
Area or polygon objects
Vector Data Structure
Points, lines and polygons
Raster Data Structure
Ratio of the size of the entity represented on a map to the size of the
entity in reality.
10km road can be represented by 1cm line on a map.
• 1cm on the map is equal to 1,000,000cm in reality.
• Scale = 1:1,000,000
• Smaller scale -> less detailed
100km road can be represented by 1cm line on a map.
• 1cm on the map is equal to 10,000cm in reality.
• Scale = 1:10,000
• Larger Scale - > more detailed
Larger Scale Smaller Scale
3. Dot Map
Plots point locations to show the spatial distribution of the
4. Symbol Maps
Use symbols of various sizes
and shapes to represent
variations of an attribute.
“The National Public Toilet Map
is part of the Australian
government's National Continence
Management Strategy (NCMS). The
map allows more Australians with
urinary and fecal incontinence
problems to live and participate in
their communities with dignity and
confidence, by making it easier for
them to find information about the
location of public toilets.“