Transcript lecture 6 ppt

Introduction to Geographic Information Systems
Fall 2013 (INF 385T-28620)
Dr. David Arctur
Research Fellow, Adjunct Faculty
University of Texas at Austin
Lecture 6
October 3, 2013
Spatial Data and
Geoprocessing
Outline

Attribute extraction

Feature location extraction

Location proximities

Geoprocessing tools

ModelBuilder
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Lecture 6
ATTRIBUTE EXTRACTION
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Attribute query extraction
You have tracts for an
entire state, but want
tracts 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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Lecture 6
FEATURE LOCATION
EXTRACTION
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Select by location


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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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Lecture 6
LOCATION PROXIMITIES
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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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Lecture 6
GEOPROCESSING TOOLS
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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
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Data management
 Generalization – dissolve

General
 append
 merge
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Accessing tools

Geoprocessing menu
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Accessing tools
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ArcToolbox
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Accessing tools

Search window
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Clip vs. Select By Location
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Clip
 Clean edges
 Looks good

Select By Location
 Dangling edges
 Better for geocoding
(chapter 8)
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Dissolve
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Combines adjacent polygons to create new,
larger polygons
Uses common field value to remove interior
lines within each polygon, forming the new
polygons
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Aggregate (sums) data while dissolving
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Dissolve
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Create regions using US states
 Use SUB_REGION field to dissolve
 Sum population
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Dissolve
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Dissolve results

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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 schemas
do 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
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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
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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
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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
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
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Intersect
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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
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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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Lecture 6
MODELBUILDER
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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
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TIGER census tracts and municipalities
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Final map
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Tracts dissolved to create neighborhoods
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Crosswalk table

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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
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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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