introduction to geographic information systems

Introduction to GeographicInformation Systems

Dr. Larry Teeter

What is a GIS?

Geospatial technologies are technolo-gies for collecting and dealing with geographic information. There are three main types:

Global Positioning SystemsRemote SensingGeographic Information Systems

One of a Set

Defining GIS

• Different definitions of a GIS have evolved in different areas and disciplines

• All GIS definitions recognize that spatial data are unique because they are linked to maps

• A GIS at least consists of a database, map information, and a computer-based link between them

"A geographic information system is a special case of information systems where the database consists of observations on spatially distributed features, activities or events, which are definable in space as points, lines, or areas. A geographic information system manipulates data about these points, lines, and areas to retrieve data for ad hoc queries and analyses" (Dueker, 1979, p 106).

Definition 1: Dueker’s Feature Model

Definition 2: A GIS is an information system

"An information system that is designed to work with data referenced by spatial or geographic coordinates. In other words, a GIS is both a database system with specific capabilities for spatially-referenced data, as well as a set of operations for working with the data" (Star and Estes, 1990, p. 2).

Definition 3: Paul Bolstad’s Definition

(author of class text)“a computer-based system to aid in the

collection, maintenance, storage, analysis, output, and distribution of spatial data and information”

Definition 4: GIS is a multi-billion dollar business.

“The growth of GIS has been a marketing phenomenon of amazing breadth and depth and will remain so for many years to come. Clearly, GIS will integrate its way into our everyday life to such an extent that it will soon be impossible to imagine how we functioned before”

We usually understand GIS to be computer-facilitated system

GIS is NOT only software/hardware

Also includes:

•Trained personnel

•Supporting Institution

•Protocols for use

Why Learn GIS?..... Because GIS is Everywhere

Why computerize manual methods? 

•To bring together data from multiple sources (synthesis)

•Analytical power•measure distance, density, area•overlay and buffer•adjacency and proximity•vicinity (neighborhood)•networks•intervisibility

•Flexibility

•Output Quality

Why GIS?

• Resource depletion/degradation

• Increased problem complexity

• Demands by the body politic

• Improved capabilities• Increased competition

Why GIS?

• Expanded capabilities - do the heretofore impossible

• Improved efficiency - reduce speed of analysis 10-fold or more

Why GIS?Traffic Information

Monitoring and Mapping Sea Icein near Real Time

Why GIS?

Pavement quality inventory and monitoring

Why GIS?

Sustaining Lobster Fisheries in Penobscot Bay

Why is it important? Fisheries stocks dwindling, lobster an economic mainstay with sustainable harvests

From Observations and Process Knowledge to Prediction and

Action

Where did GIS come from?

• GIS is built upon knowledge from geography, cartography, computer science and mathematics

• Geographic Information Science is a new interdisciplinary field built out of the use and theory of GIS

Basic Concepts of a GIS

- spatial data from different data sources are registered to same scale to form data planes (layers)

- These data are used together (overlaid) toproduce a variety of derived information

- data layers resource manager might use:

land ownership transportation networksright of way utilitiesland use vegetation coversurface water endangered specieselevation soil typejurisdictional boundaries pest & disease

Questions a user might ask of a GIS:

-Where is object A (RCW cavity trees)?

-Where is A in relation to place B?

-How many occurrences of type A are within distance X of B?

-What is the value of function Z (distance from parking area) at position X?

-How large is B (campground area, perimeter)

A Brief History of GIS• GIS’s origins lie in thematic cartography • Many planners used the method of map

overlay using manual techniques • Manual map overlay as a method was first

described comprehensively by Jacqueline Tyrwhitt in a 1950 planning textbook

• McHarg used blacked out transparent overlays for site selection in Design with Nature

A Brief History of GIS (cont.)• The 1960s saw many new forms of geographic

data and mapping software

• Computer cartography developed the first basic GIS concepts during the late 1950s and 1960s

• Linked software modules, rather than stand-alone programs, preceded GISs

A Brief History of GIS (cont.)

• Computerized GIS began in mid - 60's- CGIS - 1964- MLMIS - 1969- FRIS - early 70's

- required mainframe computers- mini computers made technology more

accessible (early 80's)

A Brief History of GIS (cont.)

• GIS was significantly altered by (1) the PC and (2) the workstation

• During the 1980s, new GIS software could better exploit more advanced hardware

• User Interface developments led to GIS's vastly improved ease of use during the 1990s

• During the 1980s, new GIS software could better exploit more advanced hardware

Features as Objects• The standard feature model divides a mapped

landscape up into features, that can be points, lines, or areas.

• Almost all human activity and natural phenomena are spatially distributed, so can be studied using a GIS.

• A GIS uses map features to manage data.

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Figure 1.2 The Feature Model: Examples of a point feature (elevation bench mark), a line feature (riv-er) and an area feature (lake).

POINT LINE AREA

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