Lecture 4

Data

Why GIS?

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)

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

Hardware Software Procedures People with skills to complete tasks Data

Hardware

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

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

Data input – paper maps, GPS, images Data management - edit and quality Query - Asking map questions Analysis - Spatial, tabular and statistical

analysis Map overlay Distance calculations

Data output - Map making, on screen, paper, internet

People with spatial knowledge Data entry Data quality Analyst Developer / Programmer Database manager Web developer Project manager GIS managerwww.gjc.org - GIS jobs listing

Data types Maps and Layers Vector Raster TIN 3D Text Metadata

Data storage formats Maps and layers

Mxd lyr

Vector Geodatabase, shapefile, coverage DXF, DWG DGN

Raster GRID, sid, img, gif, jpeg

Tables Geodatabase, dbf,

3D TIN format

Vector data Point - x, y Line - list of x, y coordinates Polygon - list of lines that form a closed area

Points

4753456 6234124753436 6234244753462 6234784753432 6234824753405 6234294753401 6235084753462 6235554753398 623634

Lines Polygons

Vector layers

Feature class Group of points, lines, or polygons Has a theme-rivers, streets, cities, lakes, states… Makes a layer

Point feature class

Line feature class

Polygon feature class

Shapefile Three files, .shp, (.dbf, .shx) Files contain either points, lines, or polygons

Layer files File for one layer, stores its symbology .lyr extension, streets.lyr Add to any map or share with friends No data

Pointer to data Symbols

Geodatabase One file - Access format .mdb file Point, line, & polygon feature classes Tables too

What is a database Storage format Container for tables of data Allows queries The sales table contains five tables

Table structure Fields Rows Cells

A feature class table Has a geometry field You can’t see the actual values, too big

Field menu Sort

Options menu

Select By Attributes

Build a SQL expression Field, Operator, Value to search for

Records get selected Pop90_SQMI < 30

Features get selected too Pop90_SQMI < 30

Make table steps 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 Make an access database

Convert a shapefile Build relationships with other tables Add fields Calculate fields Join fields