Lecture 4
Data
Why GIS?
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Ask questions
Solve a problem
Support a decision
Make Maps
Involve others, share data, procedures, ideas
What is a GIS?
GISs are simultaneously the telescope, the
microscope, the computer, and the Xerox
machine of regional analysis and synthesis
of spatial data. (Ron Abler, 1988)
Definition 1: A GIS is a toolbox
"a powerful set of tools for storing and retrieving
at will, transforming and displaying spatial
data from the real world for a particular set of
purposes"
(Burrough, 1986, p. 6).
"automated systems for the capture, storage,
retrieval, analysis, and display of spatial
data." (Clarke, 1995, p. 13).
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: GIS is an approach to
science
Geographic Information Science is research
both on and with GIS.
"the generic issues that surround the use of
GIS technology, impede its successful
implementation, or emerge from an
understanding of its potential capabilities."
(Goodchild, 1992)
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Definition 4: GIS plays a role in society
Nick Chrisman (1999) “organized activity by
which people measure and represent
geographic phenomena, and then
transform these representations into other
forms while interacting with social
structures.”
Components of a GIS
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Hardware
Software
Procedures
People with skills to complete tasks
Data
Hardware
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Computer, CPU, memory, and monitor
Modem and internet connection
Data collection devices, GPS, handheld data
Scanner or digitizing table
Plotter and printer
Web Server
Software
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GIS software – range of functions
Software extensions – add functions
Data viewers – least functionality
Single purpose software – make parcel maps
Software for the web – ATM, House locators
Non-GIS software - database, statistics,
image processing
Procedures
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Data input – paper maps, GPS, images
Data management - edit and quality
Query - Asking map questions
Analysis - Spatial, tabular and statistical
analysis
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Map overlay
Distance calculations
Data output - Map making, on screen, paper,
internet
People with spatial knowledge
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Data entry
Data quality
Analyst
Developer / Programmer
Database manager
Web developer
Project manager
GIS manager
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www.gjc.org - GIS jobs listing
Data types
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Maps and Layers
Vector
Raster
TIN
3D
Text
Metadata
Data storage formats
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Maps and layers
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Vector
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GRID, sid, img, gif, jpeg
Tables
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Geodatabase, shapefile, coverage
DXF, DWG DGN
Raster
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Mxd
lyr
Geodatabase, dbf,
3D
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TIN format
Vector data
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Point - x, y
Line - list of x, y coordinates
Polygon - list of lines that form a closed area
Points
4753456
4753436
4753462
4753432
4753405
4753401
4753462
4753398
Lines
623412
623424
623478
623482
623429
623508
623555
623634
Polygons
Vector layers
Feature class
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Group of points, lines, or polygons
Has a theme-rivers, streets, cities, lakes, states…
Makes a layer
Polygon feature class
Point feature class
Line feature class
Shapefile
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Three files, .shp, (.dbf, .shx)
Files contain either points, lines, or polygons
Layer files
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File for one layer, stores its symbology
.lyr extension, streets.lyr
Add to any map or share with friends
No data
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Pointer to data
Symbols
Geodatabase
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One file - Access format .mdb file
Point, line, & polygon feature classes
Tables too
What is a database
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Storage format
Container for tables of data
Allows queries
The sales table contains five tables
Table structure
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Fields
Rows
Cells
A feature class table
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Has a geometry field
You can’t see the actual values, too big
Field menu
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Sort
Options menu
Select By Attributes
Build a SQL expression
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Field, Operator, Value to search for
Records get selected
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Pop90_SQMI < 30
Features get selected too
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Pop90_SQMI < 30
Make table steps
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Get or make a database
Make a table
Add fields
Add records
Add values
Make a personal geodatabase
A .mdb file is Microsoft Access format
Make a new table in the database
Name it and default configuration
Add fields, type in name and type
Data Types and Length
Drag the table to ArcMap for editing
Add Editor toolbar, Start editing
Empty table to start, start typing
Type a value into a cell
Type in all values
Stop editing, save edits
Turn off Editor toolbar
Make a Geodatabase exercise
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Make an access database
Convert a shapefile
Build relationships with other tables
Add fields
Calculate fields
Join fields