This document provides a short introduction to Geographic Information Systems (GIS). It discusses the purposes of GIS, including using GIS to understand phenomena that have both geographic and temporal dimensions. It also describes how GIS allows users to enter, analyze, and present georeferenced data. The document outlines how GIS represents real world features through models like maps and databases and discusses spatial databases specifically. It positions GIS as existing at the intersection of geography and information science and technology.

1. A Short Introduction to
Geographic Information Systems
Xiaogang (Marshall) Ma
School of Science
Rensselaer Polytechnic Institute
Tuesday, January 22, 2013
GIS in the Sciences
ERTH 4750 (38031)

2. Acknowledgements
• This lecture is partly based on:
– Huisman, O., de By, R.A. (eds.), 2009. Principles of
Geographic Information Systems. ITC Press,
Enschede, The Netherlands
– Fox, P., 2012. Introduction to Geographic Information
Systems for Science. Course lecture at RPI, Troy
2

3. Contents
• 1 The purpose of GIS
• 2 The real world and representations of it
• 3 GIS as a domain of science and technology
• 4 Seven levels of GIS competence
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4. 1 The purpose of GIS
• A few example scenarios
• An urban planner might like
to find out about the urban
fringe growth in her/his city,
and quantify the population
growth that some suburbs
are witnessing. S/he might
also like to understand why
it is these suburbs and not
others.
Urban fringe, Waitara, New Zealand
Image courtesy of Quentin Christie
4

5. • A biologist might be
interested to determine
how widespread the
invasive Asian clam in
Lake George was, and to
develop and implement an
eradication plan.
1 The purpose of GIS
Asian clam identified in Lake George, NY
Image courtesy of lakegeorge.com
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6. • A geological engineer
might want to identify the
best localities for
constructing buildings in an
area with regular
earthquakes by looking at
rock formation
characteristics.
1 The purpose of GIS
Rock outcrop, North San Francisco
Image courtesy of Pascal Calarco
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7. • A forest manager might
want to optimize timber
production using data on
soil and current tree stand
distributions, in the
presence of a number of
operational constraints,
such as the requirement to
preserve tree diversity.
1 The purpose of GIS
Timber production
Image courtesy of futureforest.eu
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8. 1 The purpose of GIS
• Various professionals work with data that relates to space,
typically involving positional data.
• Positional data determines where things are, or perhaps
where they were or will be.
Abraham LincolnThomas JeffersonGeorge Washington
They worked on ‘positions’ (land survey) before entering politics
Images courtesy of wikipedia.org 8

9. 1 The purpose of GIS
• More precisely, those professionals’ questions are related
to geographic space, which have positional data relative to
the Earth’s surface (georeferenced data).
– There are also positional data of a non-geographic nature.
• A Geographic Information System (GIS) is a computerized
system that helps in maintaining and displaying data about
geographic space.
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10. 1.1 Some fundamental observations
• Our world is constantly changing, and not all changes are
for the better.
– Natural causes: e.g., volcanic eruptions
– Human causes: e.g., land use changes
– Mix / Unclear causes: e.g., El Niño / La Niña events
Grimsvotn volcano, May 21, 2011
Image courtesy of AP / Jon Gustafsson
U.S. Drought of 2012
Image courtesy of The NY Times / Mashid Mohadjerin
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11. 1.1 Some fundamental observations
• We, humans, want to understand what is going on in our
world, and to take action(s).
• The fundamental problem in many uses of GIS is that of
understanding phenomena that have (a) a geographic
dimension, and (b) a temporal dimension.
– Spatio-temporal: be of/in space and time
“Everything that happens, happens somewhere in
space and time. ”
-- Michael Wegener (University of Dortmund)
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12. 1.1 Some fundamental observations
Drought’s Footprint (1930 to present)
Image source: National Climatic Data Center, NOAA
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13. 1.1 Some fundamental observations
The maps show current and projected forest types. Major changes are
projected for many regions. For example, in the Northeast, under a mid-
range warming scenario, the currently dominant maple-beech-birch
forest type is projected to be completely displaced by other forest types
in a warmer future.
Projected shifts
in forest types
Image source:
http://nca2009.globalchange.gov/
projected-shifts-forest-types
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14. 1.2 Definition of GIS
• We may distinguish three important phases of working with
georeferenced data:
– Data preparation and entry
– Data analysis
– Data presentation
• The three phases may be repeated a number of times
before we are satisfied with the results.
• We can define a GIS as a computerized system that
facilitates the phases of data entry, data analysis and data
presentation especially in cases when we are dealing with
georeferenced data.
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15. 1.3 Spatial data and geoinformation
• Data are representations that can be operated upon by a
computer.
• Metadata are data about data.
• Spatial data are data that contain positional values.
• Geospatial data are spatial data that are georeferenced.
– In the context of GIS, spatial data and geospatial data are regarded
as synonyms of georeferenced data.
• Information is the meaning of data as interpreted by
human beings.
• Geoinformation is information that involves interpretation of
spatial data.
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16. 1.3 Spatial data and geoinformation
Image courtesy of Peter Fox
Data Information Knowledge
Context
Presentation
Organization
Integration
Conversation
Creation
Gathering
Experience
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17. 1.3 Spatial data and geoinformation
• In GIS, a wider view of QUALITY is important for several
reasons:
– Even source data have been subject to strict quality control, errors
are introduced when these data are input to a GIS.
– A GIS database normally contains data from different sources of
varying quality.
– Most GIS analysis operations will themselves introduce errors.
– Uncertainty in decision-making depends upon quality of base data
and derived information.
– … …
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18. 1.3 Spatial data and geoinformation
Comparison of
seven available
digital databases
of the streets in
part of Goleta,
CA, USA
(Goodchild 2011)
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19. 2 The real world
and representations of it
• When dealing with data and information we are usually
trying to represent some part of the real world as it is, as it
was, or perhaps as we think it will be.
– We say ‘some part’ because the real world cannot be represented
completely.
• We use a computer representation of some part of the real
world to enter and store data, analyze the data and
transfer results to humans or to other systems.
Image courtesy of NOAA 19

20. 2.1 Modeling
• A representation of some part of the real world can be
considered a model of that part.
– This allows us to study the model instead of the real world.
• Models come in many different flavors.
– Maps
– Databases
– … …
• Most maps and databases can be considered static
models.
• Dynamic models or process models address changes that
have taken place, are taking place and may take place.
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21. 2.1 Modeling
Dynamic model: break-up of
Pangaea and formation of
modern continents
Static model: map of Pangaea
with present continents outlined
Image courtesy of Wikipedia
Image courtesy of USGS
Pangaea: a supercontinent that
existed about 300 million years ago
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22. 2.2 Maps
• The best known models of the real world are maps.
• A map is always a graphic representation at a certain level
of detail.
– The smaller the scale, the less detail a map can show.
• Cartography: science and art of map making
Map scale increasing
Images made with Google Maps
Image © Bil Keane.
Courtesy of familycircus.com
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23. 2.2 Maps
More examples of maps
Images courtesy of rpi.edu
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24. 2.3 Databases
• A database is a repository for storing large amounts of
data.
– It allows concurrent use.
– It supports storage optimization.
– It supports data integrity.
– It has a query facility.
– It offers query optimization.
• Modern database systems organize the stored data in
tabular format.
Image courtesy of
MapInfo User Guide
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25. 2.3 Databases
• A database may have many tables, and each table may
have many columns (attributes) and rows (records).
• During database design, it is determined which tables will
be present and which columns each table will have.
• The result of a completed database design is known as the
database schema.
• To define the database schema, we use a language,
commonly known as a data model.
• The definition of a model is called data modeling.
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26. 2.4 Spatial databases
• Spatial databases are a specific type of database.
– Besides traditional administrative data, they can store
representations of real world geographic phenomena for use in a
GIS.
– A spatial database, also called a geodatabase, focuses on
concurrency, storage, integrity, and querying of spatial data.
– A GIS focuses on operating on spatial data with a ‘deep
understanding’ of geographic space.
• A spatial database is used under the assumption that the
relevant spatial phenomena occur in a two- or three-
dimensional Euclidean space.
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27. 2.4 Spatial databases
• Geographic phenomena have
various relationships with each other
and possess spatial, temporal, and
thematic attributes.
• For data management purposes,
phenomena are classified into
thematic data layers.
• Spatial analysis is the generic term
for all manipulations of spatial data
carried out to improve one’s
understanding of the geographic
phenomena that the data represent.
Image courtesy of Jonathan Campbell and Michael Shin
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28. 3 GIS as a domain of science and
technology
(DiBiase et al. 2006)
Philosophy
Computer
Science
Mathematics
Statistics
Psychology
Landscape
Architecture
Engineering
Various
Application
Domains
Geography
Information
Science &
Technology
Geographic Information Science & Technology
Geographic
Information
Science
Application of
GI Science &
Technology
Geospatial
Technology
From GI System to
GI Science & Technology
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29. 3.1 Geographic Information Science
• Hmm, a broad S
– From GISystems to GIScience
– GIScience: the science behind GISystems technology
• considers fundamental questions raised by the use of systems
and technologies
• is the science needed to keep technology at the cutting edge
Courtesy: http://www.ncgia.ucsb.edu/giscc/units/u002/u002.html
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30. 3.2 Geospatial technology
• Geospatial technology / Geomatics
– Land surveying
– Remote sensing
– Cartography
– Geographic information systems (GIS)
– Global navigation satellite systems (GPS, GLONASS,
Galileo, Compass)
– Photogrammetry
– Geography
– …
30

31. • Global Positioning System (GPS)
– a system of Earth-orbiting satellites transmitting
precisely timed signals
• a similar system deployed by the Russian Federation is called
GLONASS (global navigation satellite system)
• and other systems by EU, China, India, etc.
– signals are received by a special electronic device
• the smallest versions are hand-held and even smaller
– provides direct measurement of position on the Earth's
surface
– location is expressed in latitude/longitude or other
standard system
3.2 Geospatial technology
31

32. • GPS
3.2 Geospatial technology
Image source: AP
Image source: Wikipedia
Image from WWWImage source: Wikipedia
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33. • Remote Sensing (RS)
– use of Earth orbiting satellites to capture information
about the surface and atmosphere below
– satellites vary depending on how much detail can be
seen, what parts of the electromagnetic spectrum are
sensed
– signals transmitted to Earth receiving stations where
they are transformed for dissemination as digital images
Courtesy: http://www.ncgia.ucsb.edu/giscc/units/u002/u002.html
3.2 Geospatial technology
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34. 3.2 Geospatial technology
• Two main types of RS
– Passive RS: detect natural radiation (e.g., sunlight) that
is emitted or reflected by the object or surrounding
areas
– Active RS: emits energy (e.g., laser light) in order to
scan objects and areas whereupon a sensor then
detects and measures the radiation that is reflected or
backscattered from the target
Images from:
http://www.rsgisrs.com/rs_types.htm34

35. 35
Night lights of Australia as observed by the Visible Infrared Imaging Radiometer
Suite (VIIRS) on the Suomi NPP satellite in April and October 2012

36. 36
More information: http://earthobservatory.nasa.gov/IOTD/view.php?id=80030&src=fb
Fires

37. • GISystems
– a computerized system that facilitates the entry,
analysis, and presentation of georeferenced data
• GPS and RS are primary data sources for GIS
3.2 Geospatial technology
http://shuttles.rpi.edu/
http://www.flightradar24.com/
Try these:
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38. 4 Seven levels of GIS competence
• Levels of GIS competence in ascending order:
1. Public awareness of GIS and its uses;
2. Basic spatial and computer understanding;
3. Routine use of basic GIS software;
4. Higher-level modeling applications of GIS;
5. Design and development of GIS applications;
6. Design of geographic information systems; and
7. GIS research and development.
(DiBiase et al. 2006; Marble 1997)
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