Introduction to Geographic Information Systems Fall 2013 (INF 385T- 28620) Dr. David Arctur...
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Transcript of Introduction to Geographic Information Systems Fall 2013 (INF 385T- 28620) Dr. David Arctur...
Introduction to Geographic Information Systems Fall 2013 (INF 385T-28620)
Dr. David ArcturResearch Fellow, Adjunct Faculty
University of Texas at Austin
Lecture 6October 3, 2013
Spatial Data andGeoprocessing
Outline Attribute extraction Feature location extraction Location proximities Geoprocessing tools ModelBuilder
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ATTRIBUTE EXTRACTIONLecture 6
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Attribute query extractionYou have tracts for
an entire state, but
wanttracts for one
county only
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Attribute query extraction Select tracts by County FIPS ID
Cook County = 031
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Attribute query extraction Cook County tracts
selected Export to new feature
class or shapefile
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Export selected features Right-click to export selected features
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Add new layer Cook County tracts
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FEATURE LOCATION EXTRACTION
Lecture 6
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Select by location Powerful function unique to GIS Identify spatial relationships between
layers Finds features that are within another
layer
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Select by location Have Cook County census tracts
but want City of Chicago only Can’t use Select By Attributes No attribute for Chicago
Use “Municipality” layer City of Chicago is a municipality within
Cook County
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Select by location Select “Chicago” from municipalities
layer
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Select by location Selection, select by location
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Export selected features
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LOCATION PROXIMITIESLecture 6
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Points near polygons Health officials want to know polluting
companies near water features
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Points near points School officials want to know what
schools are near polluting companies
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Polygons intersecting lines Transportation planner wants to know
what neighborhoods are affected by construction project on major highway
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Lines intersecting polygons Public works official wants to know
what streets or sidewalks will be affected by potential floods
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Polygons completely within polygons City planners want to know what
buildings are completely within a zoning area.
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GEOPROCESSING TOOLSLecture 6
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Geoprocessing overview GIS operations to manipulate data Typically take input datasets,
manipulate, and produce output datasets
Often use multiple datasets
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Common geoprocessing tools Analysis
Extract – clip Overlay – intersect and union
Data management Generalization – dissolve
General append merge
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Accessing tools Geoprocessing menu
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Accessing tools ArcToolbox
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Accessing tools Search window
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Clip vs. Select By Location Clip
Clean edges Looks good
Select By Location Dangling edges Better for geocoding
(chapter 8)
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Dissolve Combines adjacent polygons to create
new, larger polygons Uses common field value to remove
interior lines within each polygon, forming the new polygons
Aggregate (sums) data while dissolving
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Dissolve Create regions using US states
Use SUB_REGION field to dissolve Sum population
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Dissolve
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Dissolve results States dissolved to form regions Population summed for each region
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Append Appends one or more datasets into an existing dataset Features must be of the same type Input datasets may overlap one another and/or the
target dataset TEST option: field definitions of the feature classes
must be the same and in the same order for all appended features
NO TEST option: Input features schemasdo not have to match the target feature classes’ schema
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Append DuPage and Cook County are
combining public works and need a new single street centerline file.
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Append Append will add DuPage streets to
Cook County streets
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Resultant layer One street layer (Cook County) with all
records and field items
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Merge Combines multiple input datasets of
the same data type into a single, new output dataset Illinois campaign manager needs a single
voting district map but wants to preserve the original layers
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Merge
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Resultant layer New voting district layer
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Union Overlays two polygon layers
Resulting output layer has combined attribute data of the two inputs
Contains all the polygons from the inputs, whether or not they overlap
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Union Neighborhoods and ZIP Codes
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Union
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Union Better describes characteristics of a
neighborhood Central business district 15222 vs. 15219
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Union Attributes tables contain different fields
and data
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Union results
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New polygons with combined data
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Union vs. Merge vs. Dissolve
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Operation # Input Feature Classes
Change in Geometry
Schema Restrictions
Union Multiple Combines all input geometries
Includes all fields from all input feature classes; input tables do not have to be identical
Merge Multiple Combines all input geometries
Input tables must be identical; retains one set of attributes
Dissolve Single Combines feature geometries based on shared attribute values
N/A – single feature class schema
Intersect Computes a geometric intersection of
the input features Features (or portions of features that
overlap in all layers and/or feature classes) will be written to the output feature class
Inputs can have different geometry types
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Intersect City manager needs to know what
buildings intersect flood zones and wants the flood data attached to each intersecting building
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Intersect
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Intersect result Only building polygons that intersect
flood zones with combined data fields
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MODELBUILDERLecture 6
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ModelBuilder overview Models automate and string tools together Example: You have census tracts for a county
and want to create neighborhoods for a city Some steps are needed to create
neighborhoods Join a crosswalk table to the tracts map layer Dissolve tracts to create neighborhoods using
the dissolve column in the crosswalk Remove the join so that the model can be
rerun if necessary You run the model for this workflow with one
click of a button
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Starting map TIGER census tracts and municipalities
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Final map Tracts dissolved to create
neighborhoods
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Crosswalk table Neighborhood names
are not included with the census tracts, so a crosswalk table was created with the name of neighborhood for each census tract
Some neighborhoods are made of multiple tracts
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Set geoprocessing options Geoprocessing > Geoprocessing
Options
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Create a new toolbox Catalog
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Create a new model Right-click Toolbox > New > Model
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Add tool to model Add Join tool
To join crosswalk table to tracts…
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Set parameter for Join tool Joins crosswalk table to census tracts
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Model steps
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Add join
Dissolve Remove join
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Finished model
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Summary Attribute extraction Feature location extraction Location proximities Geoprocessing tools ModelBuilder
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