GIS: Geography InformationGIS: Geography Information
SystemsSystems

What is GIS?
a computer-based information system used to:a computer-based information system used to:
What is GISWhat is GIS
capture,capture,
manage,manage,
update,update,
analyze,analyze,
display, anddisplay, and
output spatial data and informationoutput spatial data and information
to be used in a decision making contextto be used in a decision making context
GIS (Geographical Information System is:GIS (Geographical Information System is:

What is GIS?
Components of a GISComponents of a GIS
HardwareHardware
SoftwareSoftware DataData
PeoplePeople ApplicationsApplications
GIS

What is GIS?
Geography Brings Data TogetherGeography Brings Data Together
Multiple Data Layers
Geographically Referenced
Common Coordinate System
Provides basis for:
• Data Integration
• Systematic Analysis
• Customized Maps

What is GIS?
GIS Data Model
A layer-cake of information

What is GIS?
The GIS Data Model:The GIS Data Model:
ImplementationImplementation
Geographic Integration of InformationGeographic Integration of Information
Digital Orthophoto
Streets
Hydrography
Parcels
Buildings
Zoning
Utilities
Administrative Boundaries
• Data is organized by layers, coverages or themes (synonomous concepts), with
each layer representing a common feature.
• Layers are integrated using explicit location on the earth’s surface, thus
geographic location is the organizing principal.

What is GIS?
GIS Integrates Data & ApplicationsGIS Integrates Data & Applications
Human
Services
Town
Clerk
Senior
Center
Parks &
Recreation
Town
Manager
Finance
Health
Building Police Engineering
Assessor
Planning
Public
Works
Fire
Department

What is GIS?
A GIS Manages Two Types of DataA GIS Manages Two Types of Data
Attribute Data (what)
information that defines and
describes each feature
Spatial Data (where)
cartographic features
points, lines & polygons

What is GIS?
Spatial and Attribute DataSpatial and Attribute Data
• Spatial data (where)
– specifies location
– stored in a shape file, geodatabase or similar geographic file
• Attribute (descriptive) data (what, how much, when)
– specifies characteristics at that location, natural or human-created
– stored in a data base table
– It is information that is additional to geographical location.
(Spatial Data) E.g. Names, descriptions, labels, statistics,
measurements, categories, codes, dates, symbology.
GIS systems traditionally maintain spatial and attribute data
separately, then “join” them for display or analysis for
example, in ArcView, the Attributes of … table is used to link
a shapefile (spatial structure) with a data base table
containing attribute information in order to display the attribute
data spatially on a map

What is GIS?
The GIS Model: LayeringThe GIS Model: Layering
roads
hydrology
topography
Here we have three layers or themes:
--roads,
--hydrology (water),
--topography (land elevation)
They can be related because precise
geographic coordinates are recorded for
each theme.
longitude
latitude
longitude
longitude
latitude
latitude
Layers are comprised of two data types
•Spatial data which describes location
(where)
•Attribute data specifing what, how
much,when
Layers may be represented in two ways:
•in vector format as points and lines
•in raster(or image) format as pixels
All geographic data has 4 properties:
projection, scale, accuracy and resolution

What is GIS?
Layers are represented inLayers are represented in RasterRaster or Vectoror Vector formatformat
Raster Model
• area is covered by grid with (usually) equal-sized, square cells
• attributes are recorded by assigning each cell a single value
based on the majority feature (attribute) in the cell, such as land
use type.
• Image data is a special case of raster data in which the
“attribute” is a reflectance value from the geomagnetic
spectrum
– cells in image data often called pixels (picture elements)
• Vector Model
The fundamental concept of vector GIS is that all geographic
features in the real work can be represented either as:
• points or dots (nodes): trees, poles, fire plugs, airports, cities
• lines (arcs): streams, streets, sewers,
• areas (polygons): land parcels, cities, counties, forest, rock
type
Because representation depends on shape, ArcView refers to files
containing vector data as shapefiles

What is GIS?
0 1 2 3 4 5 6 7 8 9
0 R T
1 R T
2 H R
3 R
4 R R
5 R
6 R T T H
7 R T T
8 R
9 R
Real World
Vector Representation
Raster Representation
Concept of
Vector and Raster
line
polygon
point

What is GIS?
Street Network layer: lines Land Parcels layer: polygons
Raster (image) Layer
Digital Ortho Photograph Layer:
Digital Ortho photo: combines the visual
properties of a photograph with the positional
accuracy of a map, in computer readable
form.
Vector
Layers
Layers
Projection: State Plane, North Central Texas
Zone, NAD 83
Resolution: 0.5 meters
Accuracy: 1.0 meters
0 1500 3000 Feet

What is GIS?
Visualizations - Layer ControlVisualizations - Layer Control

What is GIS?
Different Ways to View DataDifferent Ways to View Data

What is GIS?
GIS Applications – What GIS is used forGIS Applications – What GIS is used for
• Property assessment
• Wetlands regulation
• Emergency response
• Infrastructure management
• School redistricting
• Law enforcement
• Open space planning
• Greenway planning
• Access to health services
• Forest management
• Homeland security
• Transportation planning
• Site suitability / selection
• Build-out analysis
• Search and rescue
• Plans of C & D
• Map design & production
• Watershed protection
• Permit review
• E-911
• Farmland protection
• Aquifer protection
• Archaeological research
• Economic development

What is GIS?
Examples of Applied GISExamples of Applied GIS
• Urban Planning, Management &
Policy
– Zoning, subdivision planning
– Land acquisition
– Economic development
– Code enforcement
– Housing renovation programs
– Emergency response
– Crime analysis
– Tax assessment
• Environmental Sciences
– Monitoring environmental risk
– Modeling stormwater runoff
– Management of watersheds,
floodplains, wetlands, forests,
aquifers
– Environmental Impact Analysis
– Hazardous or toxic facility siting
– Groundwater modeling and
contamination tracking
• Political Science
– Redistricting
– Analysis of election results
– Predictive modeling
• Civil Engineering/Utility
– Locating underground facilities
– Designing alignment for freeways, transit
– Coordination of infrastructure
maintenance
• Business
– Demographic Analysis
– Market Penetration/ Share Analysis
– Site Selection
• Education Administration
– Attendance Area Maintenance
– Enrollment Projections
– School Bus Routing
• Real Estate
– Neighborhood land prices
– Traffic Impact Analysis
– Determination of Highest and Best Use
• Health Care
– Epidemiology
– Needs Analysis
– Service Inventory

What is GIS?
Provide examples of data pre-processing.
(1) Georeferencing– The process of giving images in your
GIS real-world coordinates.
(2) Digitising— features on paper-based maps are traced
using a mouse type device called a cursor (it is stored
in vector format)
(3) Scanning— a scanner converts hardcopy maps and
documents into digital images.
(4) Features and Attribute tables— Attributes are attached
to the vector feature in the GIS by using a data table.
The columns are the different kinds of attributes, the
rows are the individual vector features that have been
digitized.

What is GIS?
Name and explain 4 steps to follow when creating a GIS
project.
1)Data collection. The process of finding data.
2) Data pre-processing. Data is made user-friendly by undergoing distortion
adjustments and geometric registration. (See slide on data pre-processing).
3) Data Management. Storing and updating large amounts of data and making it
easier for users to find the data.
4) Data Analysis and Manipulation. Data can be analyzed and change into
information.
ApplicationsApplications

What is GIS?
What is a GIS project? (Provide some
examples of GIS projects).
A Gis project is one that uses spatial / geographical data to answer
a particular question:
1) Agriculture: How can food production be improved?
2) Emergency: What is the fastest route to the hospital?
3) Retail: Where is the best to build a new shopping centre?
4) Marketing: Where do the people live that I want to sell to?

What is GIS?
GIS ProjectsGIS Projects
• Locating a Day-care
– intro to GIS capabilities
– illustration of a major application: site selection
• Texas Demographic growth
– manipulation of data and mapping principles
– another major application: analysis of spatial patterns with polygon
data
• Geocoding Housing Sales, or Analyzing Earthquake
Locations
– techniques and data requirements for geocoding and point
patterns
– another application: geocoding/address matching
• Creating a Census Tract layer, or a Geological Map
– editing and creating topologically consistent data
– how new data layers can be created
• Pipeline Routing
– data selection, buffering and spatial analysis
– another major application: corridor studies

What is GIS?
Perform Spatial AnalysesPerform Spatial Analyses
Find
Buildings
Within 250m of streams

What is GIS?
Public Utility ApplicationsPublic Utility Applications
Select Suitable Site for Water
Company Well
.
Water Company
Service Area
Only within undeveloped land
areas
Within undeveloped land area, only
outside buffer of polluted streams
and known point sources of pollution.
Only surface geology that shows greatest
potential for water production

What is GIS?
How does GISHow does GIS
data get stored?data get stored?Data
Decisions
Science
M
anagem
ent
Many GIS applications store digital data in a database.
GIS data is stored in a number of file formats, but the
shape file is the most common. It consists of at least
three different files that work together to store digital
vector data as shown in the table below.
A database is a storage system linked to tables.

What is GIS?
Sources of data used in a GIS
1)Primary data: Data collected in the field by physically measuring, observing and
interpreting objects e.g. GPS measurements, scanned in maps.
2) Secondary data: Data that already exists in one format or another. It is data that can
be reused e.g. maps, databases, images and aerial photographs.
Name two ways in which primary data is collected.
1) Ground-based surveys. E.g tachymetry
2) GPS

What is GIS?
What is metadata?
Metadata is data about data.
Provide some examples of metadata.
Names of people responsible for creating the data.
A textual description of the content of the data.
Dates and times of when the data was produced.
Map projection / spatial resolution used.

What is GIS?
GIS aspects that need agreement on global
standardisation include:
•The global map projections used.
•Methods of Georeferencing.
•Geographical names.
•Units of measurement used.
•Methods of processing digital data.
Data Standardisation
Growing of GIS has resulted in intense efforts at data
standardisation to establish structures and methods for
the interchange of spatial data.

What is GIS?
Data sharing offers several advantages:
•It avoids expensive repetition of data
acquisition (e.g. sensors in orbit).
•It makes a wide range of data available to
people all over the world.
•It reduces workload and cost
Data Sharing
Data sharing between organisations with different GIS
could only be achieved by data converters, transfer
standards and open file formats.

What is GIS?
Data is protected in several ways:
•Data must be secure from loss or computer failure.
•Data must be secure from fraud.
•Some files (databases) of municipalities and the
government must be kept secret.
•The police, fire brigade and ambulance have data
files that would be of interest to criminals / terrorists
and have to be protected.
Data Security
Data and information can sometimes be highly sensitive,
either for commercial or personal confidentiality or
national security. To ensure data security the data can
only be accessed with authorisation codes.

What is GIS?
Data Manipulation
Data needed for GIS comes from
many different sources. They will
need to be transformed or
manipulated in some way to
make them compatible with the
GIS system
Examples of Data Manipulation:Examples of Data Manipulation:
Creation of buffers, creation of models, integration of data layers,
conversion of data from raster and vector formats, interpolation
between points .

What is GIS?
To correct distortionsTo correct distortions
Why is it necessary to manipulateWhy is it necessary to manipulate
data in a database?data in a database?
To sharpen definitionsTo sharpen definitions
To ensure colour consistencyTo ensure colour consistency
To ensure correct latitude andTo ensure correct latitude and
longitudelongitude
Linked database tableLinked database table
Spatial dataSpatial data

What is GIS?
Data Integration
What are the problems of integrating data?
Maps have different scales
Maps have different projections
Maps have different georeferences
What is the importance of integrating
data?
A summary of integrated data is
produced and is easier to
understand
Data integration involves the combination of two or more
layers in order to create a new one.

What is GIS?
Data Querying
You can begin to ask questions:
GIS allows querying in order to answer Geographical questions
and help solve complex problems. It’s displayed graphically!
The vegetation layer is compared with the soil data layer. The shrubs
and sand areas are overlaid and only the areas adhering to the query
are shown.

What is GIS?
Answers to Simple QuestionsAnswers to Simple Questions
?
Visualize spatial
relationships
Answer questions
about what “it” is
Answer questions
about where things
are
Ad hoc queries are one of the
most important and basic of all
GIS functions
Ad hoc queries are one of the
most important and basic of all
GIS functions

What is GIS?
• That were sold in
the past 3 years
• For more than
$200,000
Queries - Class of FeaturesQueries - Class of Features
• Select all parcels
in a subdivision

What is GIS?
A buffer refers to an area around a point, line or polygon.
You can demarcate a buffer area of for example 3 km around a place on
the map.
EXAMPLES OF BUFFERING: What is the total number of customers
within 10 km of this shopping mall? Which areas will be affected by a 1m
rise in sea level? Which residential areas will be affected by a nuclear
fallout affecting a radius of 60 km from the nuclear power station?
MapInfoMapInfo
Buffering

What is GIS?
Statistical Analysis
Information such as:
Statistical Analysis is used to investigate GIS
data and assist in the identification of
additional information.
Spatial patterns
Spatial trends
Climatic averages e.g. temperature and
rainfall
Which layers would GIS researches use to
determine the risk of a landslide:
Altitude Slope angle
Rock type Land cover
Slope exposure Distance from rivers
Profile curvature Surface curvature
Distance from the road Drainage Basin

What is GIS?
What remote sensing is used for:
Remote sensing is obtaining data from a distance without touching the object.
Instruments used to collect the information are the camera, radar, sonar, thermal
and electro-optical sensors.
Remote sensing is used to study weather patterns, climate change, urban change,
the atmosphere, landscapes, ecosystems, human impact on the environment, the
oceans and hydrology.

What is GIS?
Spatial ResolutionSpatial Resolution
• Satellite images are captured in digital format.
• They consist of a very fine grid of squares called
‘picture cells’ or ‘pixels’. (Raster data)
• Coarse (low) resolution if the pixel covers a
large area on the ground
• Fine (high) resolution covers a smaller area
on the ground.
Spatial Resolution refers to the size of an object that can
be recorded; the most usual method is the pixel size.

What is GIS?
Spectral ResolutionSpectral Resolution
Spectral resolution refers to the width of the wavelength intervals that are being
measured in the electromagnetic spectrum.
Remote sensors can collect data in the visible part of the spectrum (to provide
images such as aerial photographs).
Other sensors may collect data in the invisible sectors like infrared (seen below)
and ultraviolet.

What is GIS?
Vertical Aerial Photograph – Taken from
above, camera is pointing vertically
downwards.
High Oblique Aerial Photograph – Horizon
is visible. Camera is tilted at 68 degrees.
Low Oblique Aerial Photograph – Horizon is not
visible. Camera is tilted at 30 degrees.