Analysis in 9.2:

Overlay

Analysis

• Usually starts with selection but selection can be used throughout an analysis

• The main tools for analysis are, however, the Analysis Tools from the toolbox

• What follows is– Overview of Select by location options– Overview of Analysis Tools– A problem

Sel by location: Intersect

Sel by location: Touch Bndy of…

Sel by location: Have their Center in…

Sel by location: Are completely w/in…

Sel by location: w/in a distance of…

Sel by location: are contained by…

Selection Summary

• Allow the selection of features based on criteria

• Is a pretty rich set of operations

• BUT– Some share name

with the REAL overlay operations but don’t deliver the same result

• Intersect• Within distance of• Completely contain• Completely within• Have center in• Share segment w/• Touch boundary of• Are identical to• Are crossed by

outline• Contain• Are contained by

Overlay Operations

• Overlay operations are like the “select by location” functions but not exactly the same.

• Both use two layers– Select by location just selects

features in one of the layers– Overlay operations create new

feature classes

Toolbox

Overlay: Erase• From Help: Erase feature removes a chunk of

the input feature• It is important to keep Input and Erase feature

correct or GIGO

Overlay: Union

• This computes a geometric UNION of the input and output feature classes . ALL features will be written to the output feature class with the attributes from both.

• Or: This tool builds a new feature class by combining the features and attributes of each feature class.

Overlay: Union

UNION: another view

Overlay: Identity• Computes a geometric intersection

(logic) of the input and identity features• Input features (or portions thereof) that

overlap the identity features will get their attribute features from the identity features

• To put it another way: combines the portions of features that overlap the identity features to create a new feature class.

Overlay: Identity• Computes a geometric intersection

(logic) of the input and identity features• Input features (or portions thereof) that

overlap the identity features will get attribute features from the identity features

• To put it another way: combines the portions of features that overlap the identity features to create a new feature class.

Clips by the Input feature and then UNIONS what is

left.

Overlay: Intersect• Computes the geometric

intersection of the input features or portions of features COMMON to all layers.

• This tool builds a new feature class from the intersecting features common in both feature classes. Available with any ArcGIS license.

Overlay: Intersect• Computes the geometric

intersection of the input features or portions of features COMMON to all layers.

• This tool builds a new feature class from the intersecting features common in both feature classes. Available with any ArcGIS license.

Intersect is NOTthe same as

Identity

Overlay: Symmetric Diff

• Computes a geometric intersection of the input and update features. Any features COMMON to ONLY one of the inputs will be written to the output

• Or to put it another way: This tool creates a feature class from those features or portions of features that are not common to any of the other inputs.

Overlay: Symmetric Diff

• Computes a geometric intersection of the input and update features. Any features COMMON to ONLY one of the inputs will be written to the output

• Or to put it another way: This tool creates a feature class from those features or portions of features that are not common to any of the other inputs.

This is the olive drab feature showing

through a hole in the yellow feature!

Overlay: Update

• Computes the geometric intersection of the input and update features. The attributes and geometry of the input features are replaced by the update features.

• This tool updates the attributes and geometry of an input feature class or layer by the Update feature class or layer that they overlap

Overlay: Update

• Computes the geometric intersection of the input and update features. The attributes and geometry of the input features are replaced by the update features.

• This tool updates the attributes and geometry of an input feature class or layer by the Update feature class or layer that they overlap

Overlay: Summary

IDENTITY INTERSECT SYM-DIF UNION UPDATE

Buffer

• Buffering is an additional tool used in Analysis. Not

Dissolved

Dissolved =All

Summary

• The analysis tool in ArcGIS are very powerful

• And fairly easy to understand … one at a time!

• It is use by combining the overlay and selection tools to solve a problem that is the problem!

• Exercise 7 is for you to create your own crib sheet for some of the selection and analysis functions.

• You cannot use any of the graphics or text in this PP or in the ESRI help.

• You have to digest what is in this PP and help and create your own descriptions and graphics.