what is a gis?
DESCRIPTION
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 …. …. - PowerPoint PPT PresentationTRANSCRIPT
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.