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 NOT the 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.