What is a GIS?

A geographic information system (GIS) = a computer-based tool for analyzing (and mapping) spatial or, geographic information (2D or 3D).

GIS combines database operations …

…..

GIS lets you (among other things) EXPLAIN events, PREDICT outcomes, and PLAN strategies by visualization.

things to ponder: overpopulation, deforestation, pollution, natural disasters……GIS can help us cope!

…...

Site a new business, locate the best soil for growing corn, or route the fastest way for an ambulance…….GIS is your tool

Maps are not new…but…now they are “alive” and can be made reasonably fast

Components of a typical GIS Hardware - stand-alone

or networked? Software - DBMS with

geographic capabilities Data - digitized, or

purchased? People YOU!

(organized?) Methods - think it

through first - then act

How GIS works...

World is “stored” as linked thematic layers….the layers have known geographic locations

a geographic location is a longitide and latitude in some coordinate system. (UTM ?), address, road names, etc.

Models - Raster or Vector

Raster - grid cells (pixels) of a certain dimension (resolution)

Vector - points, lines, polygons

Real world

Advantages/disadvantages of the Raster model & Vector model Sometimes inefficient to

store (eg.big lake) sometimes faster than

vector . better for complex

continuous data. “smoother” 3d analysis. “jaggy” appearance ….so use both!

Looks better than raster (less “jaggy”)

efficient storage (eg. big lake)

“jagged” 3d analysis linear features do not

occupy space…(fence) more correct ….so use both!

The 5 tasks of a GIS

InputManipulationManagementQuery and AnalysisVisualization

Input…...

Digitize or scan existing maps.

Import digital data.

Import digital imagery .

GPS.

Manipulation…

…..data fussing……the “not fun” part, and often very time consuming……moving of lines that don’t fit, change in projections, weeding out data of no use, cleaning up scanned maps….etc.

Management…

Will the GIS system still be useful to others?

If the answer is NO, are you managing the GIS properly to store, organize, and manage the data?ARC’s approach is a RELATIONALdesign in the form of a collection of TABLES with common fieldsthat can be linked from TABLE to TABLE….

Management…

Query and Analysis…

Ask simple questions: who owns that big lot?…….what isthe distance from here to the big lot?……..is the big lotproperly zoned for the planned development?…….Howbig is the big lot?

Ask more complex analytical questions: is the big lot closeto any potential problems?………should the planned development require more land?..is there any similar plotsnearby?…….will the planned development have anegative impact on traffic flow?……..and so on…….yourimagination and insight should rule….not the GIS!!!

Query and Analysis…

…..use the GIS to look for PATTERNS and TRENDS and use it for“WHAT IF” scenarios…… proximity analysis….

Query and Analysis…

……overlay analysis….

Visualization…

….now for some cartography…….use an appropriateamount of time…….who will use the map and for whatpurpose???

Related Technologies

Desktop Mapping - focus is on map creation…..ARCVIEW

CAD - much simpler than GIS (design) Remote Sensing (including GPS) - more

complex than GIS but with less focus on database management

DBMS - Does you data base require 2D or 3D visualization?

Some uses……...

Realtors……tiled roofs and 5 bedrooms……then list houses in particular area matching the request……….then price and distance to schools can be additional constraints...

…..and narrow it down !

More uses

Improved Organizational Integration……

And some more Make Better Decisions………..just

remember that the quality of the DATA and the insight and imagination of the RESOURCE MANAGER rule……the GIS is the tool towards objective and rational decision making.

…..more……Making Maps

Ensure that the all components of the “system” keep producing.

The “chain” is only as good as the weakest link.