Introduction-Overview • Why use a GIS? • What can a GIS do...
Transcript of Introduction-Overview • Why use a GIS? • What can a GIS do...
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Introduction-Overview
• Why use a GIS?• What can a GIS do?• How does a GIS work?• How does a GIS work?
• GIS definitions
• Spatial (coordinate) data model
• Relational (tabular) data model( )
Gary Weaver intro_gis.ppt 1
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Why use a GIS?
• An extension of the paper map, but much more than a map, as you will see.• GIS uses the analytical power of the computer to complete complex tasks.• Computer's storage power to manage large data sets. p g p g g• Integration of many different types of data from many different sources.• GIS maps a variety of different data to the same coordinate space (combination).• Digital media are more stable than paper media, and easier to distribute via the net.Digital media are more stable than paper media, and easier to distribute via the net.
• Faster and easier update. • Creation and use of "one-time" maps. • Tailor-made mapsTailor made maps.
• Elimination of some user bias.
• GIS brings new tools for thinking differently about geographic data• GIS brings new tools for thinking differently about geographic data.
Gary Weaver intro_gis.ppt 2
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
What can a GIS do?
• Generically• Locate geographic features based on properties. • Identify and analyze properties of geographic features based on location.
• Specifically• Estimate economic effects of land-use regulation. • Determine the optimal locations of new businesses• Determine the optimal locations of new businesses.• Generate optimal routing and scheduling delivery and repair services. • Determine the ground area covered by a new cellular phone network. • Delineate watershed boundaries for estimates of sedimentation effects. • Predict vegetation types based on elevation, slope, and aspect. • Predict landslide hazard for harvest units. • Locate natural areas that need protection.• Make colorful and interesting maps.
Gary Weaver intro_gis.ppt 3
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
The GIS Model: Examples
•roadsHere we have three layers or themes:--roads,
•longitude•longitude
,--hydrology (water),--topography (land elevation)
They can be related because precise geographic coordinates are recorded for each theme.
•hydrologyLayers are comprised of two data types
•longitudey p yp
Spatial data which describes location (where)Attribute data specifying what, how much, and when
Layers may be represented in two ways:
•topography
y y p y1. in vector format as points and lines2. in raster(or image) format as pixels
All geographic data has 4 properties:
Gary Weaver intro_gis.ppt 4
•longitude
g g p p pprojection, scale, accuracy and resolution
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Examples of what a GIS can do
• Example 1: Where is a given feature or set of features? Where is Aurora Ave N?
Gary Weaver intro_gis.ppt 5
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Examples of what a GIS can do
• Example 2: Where is a particular location?Where is the corner of Aurora Ave N & N 50th St?
Gary Weaver intro_gis.ppt 6
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Examples of what a GIS can do
• Example 3: What parcels will be affected by a road resurfacing project?Which parcels are within ½ mi of Aurora between N 35th & N 50th?
Gary Weaver intro_gis.ppt 7
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Examples of what a GIS can do
• Example 4: Where are areas that meet a given complex set of criteria? What parts of the forest are located:
• on > 30% slope?
• closer than 100 ft to a stream, and• farther than 50 ft from a road,
Gary Weaver intro_gis.ppt 8
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Examples of GIS maps
topographic mapping
Gary Weaver intro_gis.ppt 9
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Examples of GIS maps
orthophoto image maps
Gary Weaver intro_gis.ppt 10
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Examples of GIS maps
surface drapes & 3-D modeling
Gary Weaver intro_gis.ppt 11
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Examples of GIS maps
classified thematic mapping
Gary Weaver intro_gis.ppt 12
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Examples of GIS maps
research documentation
Gary Weaver intro_gis.ppt 13
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
How does GIS work?
bi i f d• Combination of coordinate data
and
tabular dataeach feature has a record
Gary Weaver intro_gis.ppt 14
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
GIS definitions
• "A system of hardware, software, and procedures designed to support the capture, management, manipulation, analysis, modeling and display of spatially-referenced data for solving complex planning and management problems."
• A working GIS integrates five key components:
f• hardware,
• people, and• data, • software,
• methodsp p
Gary Weaver intro_gis.ppt 15
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Spatial Data Model
GIS are driven by spatial data - 2 basic spatial data models exist
• VectorTh f d l f GIS i h ll hi f• The fundamental concept of vector GIS is that all geographic features in the real work can be represented either as:
• points or dots (nodes): trees, poles, fire plugs, airports, cities• lines (arcs): streams, streets, sewers,( ) , , ,• areas (polygons): land parcels, cities, counties, forest, rock type • Because representation depends on shape, ArcGIS refers to files
containing vector data as shapefilesR t• Raster
• area is covered by grid with (usually) equal-sized, square cells• attributes are recorded by assigning each cell a single value based on
the majority feature (attribute) in the cell, such as land use type.j y ( ) , yp• Image data is a special case of raster data in which the “attribute” is a
reflectance value from the geomagnetic spectrum• cells in image data often called pixels (picture elements)
Gary Weaver intro_gis.ppt 16
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Vector Data Model
• Characteristics of the vector data model:
• Features positioned accurately• Features positioned accurately
• Shape of features represented correctly
• Features represented discretely (no fuzzy boundaries)
• Complex data structure (especially for •pointComplex data structure (especially for polygons) •line
•polygon
Gary Weaver intro_gis.ppt 17
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Vector Data Model
Points: represent discrete point features
Gary Weaver intro_gis.ppt 18
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Vector Data Model
Lines: represent linear features
Gary Weaver intro_gis.ppt 19
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Vector Data Model
Lines: represent linear features
• Lines start and end at nodes• line #1 goes from node #2 to node #1
• Vertices determine shape of line
Gary Weaver intro_gis.ppt 20
Vertices determine shape of line_
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Vector Data Model
Polygons: represent bounded areas
Gary Weaver intro_gis.ppt 21
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Vector Data Model
Polygons: represent bounded areas
• Polygon #2 is bounded by lines 1 & 2• Line 2 has polygon 1 on left and polygon 2 on right
Gary Weaver intro_gis.ppt 22
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Vector Data Model
Polygons: represent bounded areas
• complex data model• “arc/node topology”• arc/node topology
Gary Weaver intro_gis.ppt 23
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Vector Data Model
Types (formats) of vector data available in ArcView
• ArcGIS shapefilesArcGIS shapefiles
• ArcInfo coverages and libraries
• CAD files (AutoCAD DWG, DXF;Microstation DGN)
• StreetMap files
• Spatial Database Engine (SDE) data
• ASCII point coordinate data
Gary Weaver intro_gis.ppt 24
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Vector Data Model
• A vector data format
Shapefiles
A vector data format
• Preferred in ArcGIS• Draws fast• Fully editable in ArcGIS
• Simple in structure
• Does not use arc-node topology• “Connected” lines do not necessarily share a common node
Adj t l d t h b di• Adjacent polygons do not share common bounding arcs• Data sets are either point or line or polygon
Gary Weaver intro_gis.ppt 25
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Vector Data Model
• A older commonly found format
ArcInfo coverages
A older commonly found format
• Data model more complex
• Draws more slowly in ArcGIS
• Coordinate data not editable in ArcGIS
• Can be used in both ArcGIS and ArcInfo
P l hi• Polymorphic
• Problematic file structure (more on this later in the term)
Gary Weaver intro_gis.ppt 26
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Vector Data Model
• CAD data are very common (industry standard)
AutoCAD & Microstation CAD drawing data
• CAD data are very common (industry standard)
• DXF, DWG, and DGN formats supported in ArcGIS
• Coordinate data not editable in ArcGIS
• Frequently contain “sloppy” dataq y ppy• No enforced topology rules• Gaps in data
• Frequently contain little or no useful attribute data
Gary Weaver intro_gis.ppt 27
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Vector Data Model
• Easy to obtain from a variety of sources
ASCII coordinate data
y y• GPS• Traverse• Direct reading from maps
• OS, architecture, and application independent
Gary Weaver intro_gis.ppt 28
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Raster Data Model
• Rectangular grid of square cells
Characteristics of the raster data model:
g g q
• Shape of features generalized by cells
• Contin o s (s rface) data represented easil• Continuous (surface) data represented easily
• Simple data structure
Gary Weaver intro_gis.ppt 29
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Raster Data Model
Wi d d
Raster data are good at representing continuous phenomena
• Wind speed
• Elevation, slope, aspect
• Chemical concentration
• Likelihood of existence of a certain speciesLikelihood of existence of a certain species
• Electromagnetic reflectance (photographic or satellite imagery)
Gary Weaver intro_gis.ppt 30
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Raster Data Model
• origin is set explicitly
Raster spatial data model
• cell size is known
ll f• cell references (row/column locations)are known
• cell values are referencedto row/column location
• values represent numerical phenomena orindex codes for non-
Gary Weaver intro_gis.ppt 31
numerical phenomena
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Raster Data Model
A few different types of raster data
• digital orthophotodigital orthophoto
• digital elevation model (DEM)
Gary Weaver intro_gis.ppt 32
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Relational Database Model & Attribute Data Structures
• The “where” of GIS is determined by coordinate (map) data structures, but …
• The “what” of GIS is determined by tabular (relational database) data structures
• Thus, tabular data are just as important as coordinate data
Gary Weaver intro_gis.ppt 33
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Relational Database Model & Attribute Data Structures
Attribute data are stored in database tables.
• Tables are composed of:
• fields
and
d• records
Gary Weaver intro_gis.ppt 34
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Relational Database Model & Attribute Data Structures
You may already be familiar with relational databases
• dBase
• rBaserBase
• Access
• Excel (database functionality)
• Oracle, INFORMIX, INGRES, SQL Server
• INFO (in ArcInfo)
Gary Weaver intro_gis.ppt 35
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Relational Database Model & Attribute Data Structures
ArcGIS uses tabular data formats from dBase, ASCII text, and INFO files
• tables are stored on the drives as
• .dbf,.dbf,
• .txt, or
• in INFO directories
Gary Weaver intro_gis.ppt 36
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Relational Database Model & Attribute Data Structures
Tables can be linked and joined (“related”) by use of common values in fields
Gary Weaver intro_gis.ppt 37
CM3205 - 51 – GEOGRAPHIC INFORMATION SYSTEMS
Relational Database Model & Attribute Data Structures
V
Different types of attribute tables in ArcView
• Vector• point attribute tables• polygon attribute• line attribute• line attribute
• node attribute* • text attribute*text attribute• route & event tables*
• RasterRaster• value attribute
Gary Weaver intro_gis.ppt 38
* in ArcInfo coverage data only