Geographic Information Systems Data Analysis. What is GIS Data ?
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Transcript of Geographic Information Systems Data Analysis. What is GIS Data ?
Geographic Information Systems
Data Analysis
What is GIS Data ?
Types of GIS Systems
Raster• Features
represented as a matrix of cells over continuous space
• Each layer is one attribute
• Analysis is done by combining layers to create new layers with new values
• Cell size is critical
Vector• Each feature is a row
in a table• Define by specific
X,Y locations coordinates in space.(lat,long)
• Features can be discreet locations or events (trees or Earthquakes)
• Not as memory intensive
Raster Data• Grids represent entities
– Grids made of cells– Value applied to cell– Each grid represents one attribute– Continuous surface of a matrix of cells
• Analysis Includes:Analysis is done by combining layers to create a new layer with new cell values– Buffering/Proximity– Reclassification– Hill-shade/Slope– Interpolation– Surface Calculation
Vector (Feature) Data
• Points, Lines and Areas represent entities
– Points - City, Tree– Lines - River, Road– Areas - Forest, Lake
• Analysis includes:
– Buffering– Intersecting– Network Analysis (shortest path)
Point Data
Points represent objects that have discrete locationsUsual to small to be represented by area or polygonCan pinpoint the exact locationEg. Buildings
Spot heightsTornadoesWater samplesBusinesses
Line Data
Represent objects that have length but are too narrow to be shown as polygons
Can be broken into many segments known as ARCs
• Eg.-rivers – Roads – Railways– Bridges
Area or Polygon Data
• Defined by borders and are closed• Usually to large to be depicted as points or
lines• Can be legally defined – building lots• Administrative- countries or
counties• Naturally occurring boundaries- Ecozones
Lakes
Coordinate Systems
• A coordinate system is required to reference data to a real world location. It could be lat/long or military grid.
• ArcView transforms the image coordinates into real-world x,y coordinates. – Vector data sources stored in a real-world x,y
coordinate system. – Images/Grids stored in rows and columns of pixels-– Pixel size (resolution) is critical
• ArcView looks for georeferencing information stored with the image.
Attribute data
• The descriptive data that a GIS links to map features
• Attribute data is collected and compiled to link to specific locational data-
census data by Provinceoften comes packaged with
map data
Image Data
Data produced by an optical or electronic device. Usually originally in Raster format
Remote sensed data– Satellite & remote sensed Data– Aerial photography – Scanned data– Photographs
• Can be linked to locational data or registered to display with other themes and layers with real world coordinates
What is GIS Analysis
• From simple to Complex• Simple - Sometimes by just making
a map you are doing analysis• Complex - Sometimes we use
many layers of data to simulate real world events
Data Analysis
What do we Map in a GIS?
•Map where things are-Location Analysis•Map the most and least-Quantitative
Analysis•Map concentrations- Density•Map what is inside-Monitoring•Map what is nearby-Relationships•Map Change-Prediction