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40 Cards in this Set
- Front
- Back
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Spatial analysis
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Process of investigating patterns arising as result of processes that operate in space
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Spatial analysis adds value to geographic data by turning it into _____
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Geographic Information
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A prior knowledge
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Independent of experience
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A posteriori knowledge
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dependent upon experience
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Deduction
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Theory to observation to confirmation
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Induction
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Observation to tentative hypothesis to theory
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Types of spatial analysis
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1. Exploratory: visualization, measurement
2. Geostatistics: in search of patterns 3. Spatial modeling: prediction, forecasting |
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1st law of geography
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Everything is related to everything else, but near things are more related than distant things
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Spatial autocorrelation issues
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-Some phenomena exhibit extreme irregularity across space
-Assumes variables are dependent |
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Spatial Interpolation
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-Estimates values at any given point based on surrounding known values
-Reliant on distance decay principle -Reliant on adequate sampling of data from which to interpolate |
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Vector Analysis: Selection by Attribute
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Ex. you have tracts for an entire state, but only want tracts for one county
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Vector Analysis: Selection by Location
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Powerful, unique to GIS
-ID relationships between layers (spatial query) |
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Dissolve
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Remove unneeded info
-Attribute of features used as "dissolve" attribute |
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Vector Analysis: Proximity functions
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Modify existing features or create new features that depend on distance
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Vector Analysis: Buffer
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Region less than or equal to specified distance from one/more features
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Vector Analysis: Overlay
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2 or more maps registered to common coordinate system are SUPERIMPOSED
-Show relationships between features occupying same geographic space |
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Types of overlay: Clip
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Uses "cookie cutter" to select features
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Types of overlay: Union
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Resulting output layer has combined all attribute data of polygons in two inputs
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Types of overlay: Intersect
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Features portion of features overlapping in all layers
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Append
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Appends multiple input dataset into already existing target dataset
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Merge
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Combines input features from multiple input sources into a single, new output feature class
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Map algebra
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Mathematical way to manipulate/combine raster data sets to create a new raster
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Forms of map algebra
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-Unary operations: output = f(x)
-Binary operations: output = input_A (operator) input_B |
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AND
Ex. value1 AND value2 |
if both input values are true, the result is true
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OR
Ex. value1 OR value 2 |
if either of the inputs is true, the result is true
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NOT
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Switch true for false and false for true
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Local functions
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Map algebra that uses one cell in an input raster at a time
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Focal functions
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Use map algebra that uses all cells in user defined neighborhood in input raster
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Global funtions
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Map algebra that use all cells in an input raster
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Issues of raster overlay
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Different coordinate systems
Cell orientation Cell size |
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(2) types of spatial modeling
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1. Spatio-temporal models: dynamic in time and space
2. Cartographic models: static, combine data from multiple data layers |
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Spatio-temporal models
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1. Agent based: simulation of decisions and interactions of individual, independent agents
2. Cellular automata: use simple transition rules to determine time-step evolution of cell values |
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Cartographic models
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Provide info through combination of spatial data sets, functions and operations
-Based on set of CRITERIA -Output spatial data layer |
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Suitability analysis
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Spatial operations (ex. buffering, overlay) used to output suitability layer, ranking parcels for particular land-use
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Spatial Modeling definitions
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1. Abstraction of reality
2. Set of rules for predicting an outcome 3. Data representation of reality |
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Discrete rankings
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Either/or suitable
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Continuous rankings
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More/less suitable
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Weighting
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Defines relative value of different layers
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Ranking
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Defines relative values within same layer
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ModelBuilder
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Automates and strings functions together
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