GIS Lecture: Geoprocessing

Outline Geoprocessing Tools Model Builder

Geoprocessing Tools

Geoprocessing Tools GIS operation to manipulate data Take input data sets, manipulate, and produce output data sets Often use multiple data sets

Common geoprocessing tools Analysis Proximity - Buffer Extract – Clip Overlay – Intersect and Union Data management Generalization – Dissolve General Append Merge

Accessing tools Geoprocessing menu

Accessing tools ArcToolbox

Accessing tools Search window

Proximity Buffers

Point Proximity Buffers Point buffers are circular with a user-supplied radius

Point buffer example Drug-free zones: criminal penalties are higher for drug dealing within 1,000 feet of a school

Point buffer example Polluting company buffers Added schools Added population Data from U.S. Census and EPA website

Line Proximity Buffers Line buffers look like a worm

Line buffer example Businesses within 0.25 miles of a selected street being paved

Select features in buffer

Polygon Proximity Buffers Polygon buffers extend polygons outward and round-off corners

Polygon buffer example Parcels within 150′ of selected property Need to send notifications to adjacent land owners about a requested zoning variance at selected property (commercial land use in residential area)

Select features in buffer

Spatial Joins With Buffers - Spatially join toxic release sites to buffers - Count appears in new buffer

Multiple ring buffer Each distance produces a separate polygon.

Clip Features

Clip Uses “cookie cutter” to select features Input Clip Feature Output

Line (Arc) Clipping Input layer: Streets Clip layer: Central Business District (selected neighborhood) Output layer: Clipped Streets (within Central Business District only)

Difference Between Clipping and Select by Location Clip: Clean “cut” Select by Location Intersect: Dangle edges

Dissolve Features

Dissolve combines adjacent polygons to create new, larger polygons uses common field value to remove interior lines within each polygon, forming new polygons can also aggregate (sum) data while dissolving Input Output

Dissolve Create regions using US states Use SUB_REGION field to dissolve Sum population

Dissolve

Dissolve results States dissolved to form regions Population summed for each region

Append Features

Append Appends one or more datasets into an existing dataset features must be of the same feature type input datasets may overlap one another and/or the target dataset TEST option: fields must be the same and in the same order NO TEST option: fields do not have to match

Append Streets DuPage and Cook County are combining public works and need a new single street centerline file.

Append Streets Append will add DuPage to Cook County streets

Resultant Layer One street layer with all records and field items

Union Features

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

Union Start with ZIP codes and Neighborhoods

Union Attributes tables contain different data

Union Union neighborhoods and ZIP Codes to include the zip on each neighborhood polygon

Resultant Layer Polygons are combined with both attribute tables

Intersect Features

Intersect Computes a geometric intersection of the input features Features or portions of features which overlap in all layers

Intersect City manager needs to know what buildings intersect flood zones and wants the flood data attached to each intersecting building

Intersect

Intersect result Only building polygons that intersect flood zones with combined data fields

Model Builder

Model Builder Workflow processes can be complicated Models automate and string tools together You run a model with one click of a button

Add Functions to Model Drag and drop layers from Table of Contents and functions from ArcToolbox

Model Builder Example Run the model…

Model Builder Examples

Model Builder Examples Simple to Complex

Summary Geoprocessing Tools Model Builder