1. URBDP 422 Urban and Regional Geo-Spatial Analysis
Lecture 7: Vector Spatial Analysis
Lab Exercise 7: A Vector Analysis
January 28, 2014

2. Objectives of Lecture Introduce geoprocessing concepts
Describe geoprocessing operations
Build a model with Model Builder

3. Vector Vs. Raster Spatial Operations
Overlay analyses
Operate on spatial entities from two or more layers
It is one of the most “fundamental” of GIS operations
McHarg in 1960 used acetate map overlays
Vector overlays
combine point, line, and polygon features
computationally complex
Raster overlays
cell-by-cell comparison or integration
computationally less complex

4. Operations on the attributes of
geographic entities
The process of selection or creation of new attributes
can be formalized s a function:
Ui = f(A,B,C,D…)
U = new attribute
A,B,C.. = values of the attribute used to estimate U

5. Spatial Analysis Proximity Extract Overlay Point distance Near Buffer
clip
split
Overlay
union
intersect
Identity
erase
update

6. Proximity: Point Distance
POINTDISTANCE computes the distances between point features in one feature class to all points in a second feature class that are within the specified search radius.
ESRI 2009

7. Proximity: Near
NEAR computes the distance from each point in a feature class to the nearest arc, point or node in another feature class.
ESRI 2009

8. Proximity: Buffering
BUFFER creates a polygon feature class by generating buffer zones around input feature class features (lines, polygons, points, or nodes).
ESRI 2009

9. Proximity: Buffering Output is always a polygon feature class
The size of the buffer zone is defined in one of three ways:
By using the buffer distance to specify a constant size for all buffer zones
By specifying an item value to generate multiple buffer sizes directly
By generating the multiple sized from item values through a lookup table

10. Polygon Overlay
POLYGON OVERLAY commands involve three feature classes: an input feature class, an overlay feature class, and an output feature class created as a result of the overlay.
Input feature class features can be polygons, lines, or points.
The overlay feature class feature must be polygons.
Output features are of the same class as the input features.
polygon-on-polygon overlay - output is a polygon feature class
line-on-polygon overlay - output is line feature class
point-on-polygon overlay - output is a point feature class

11. Polygon Overlay
UNION combines all the features of both feature classes
INTERSECT Only those features in the area common to both feature classes will be preserved in the output feature class. Any data that lie outside the common area are deleted (clipped) from the output feature class.
IDENTITY All features of the input feature class, as well as those features of the identity feature class that overlap the input feature class, are preserved in the output feature class.

12. Overlay: Union
UNION - computes the geometric intersection of two polygon feature classes. All polygons from both feature classes will be split at their intersections and preserved in the output feature class.
ESRI 2009

13. Overlay: Intersect
INTERSECT - computes the geometric intersection of two feature classes. Only those features in the area common to both feature classes will be preserved in the output feature class.
ESRI 2009

14. Overlay: Identity
IDENTITY - computes the geometric intersection of two feature classes. All features of the input feature class, as well as those features of the identity feature class that overlap the input feature class, are preserved in the output feature class.
ESRI 2009

15. Overlay: Erase
Erase Features polygons define the erasing area. Input Features or portions of input features that overlap the Erase Features are not written to the output feature class.
Input Features can be points, lines, or polygons, but Erase Features must be polygons. Output Features will be of the same geometry type as Input Features.
ESRI 2009

16. Overlay: Update
UPDATE replaces the Input Features with the Update Features using a cut-and-paste operation.
Computes a geometric intersection of the Input Features and Update Features.
The attributes and geometry of the Input Features are updated by the Update Features. The results are written to the Output Feature Class.
ESRI 2009

17. Extract: Clip
Use Clip when you want to cut out a piece of one feature class using one or more of the features in another feature class as a "cookie cutter". This is particularly useful for creating a new feature class that contains a geographic subset of the features in another, larger feature class.
ESRI 2009

18. Extract: Split
Split creates new feature classes by overlaying two sets of features. Split performs a series of Clip operations, one for each output feature class. Each output feature class contains only those portions of Input Features that are overlapped by the specified polygons of the Split Features.
ESRI 2009

19. Data Management: Dissolve
Use Dissolve when you want to aggregate features based on a specified attribute or attributes. Features with the same value combinations for the specified fields will be aggregated (dissolved) into a single feature. The Dissolve fields are written to the Output Feature Class table.
ESRI 2009

20. Data Management: Merge
Allows you to “join” two adjacent or non-adjacent themes
into the same layer
Combines input features from multiple input sources (of the same data type) into a single, new, output feature class. The input data sources may be point, line, or polygon feature classes or tables.
ESRI 2009

21. Model Building Building a model helps you manage and automate your
Geo-processing work flow.
Building a model helps you manage this complexity by:
- making processes and the relationships between processes explicit,
and the model you create is updated whenever a change is made.
- setting values for the parameters of each tool, and it records this
information, making the model output easily reproducible.
- editing the structure of the model by adding and deleting processes
or changing the relationships between the processes.
- editing the parameter values defined for tools to experiment with
alternative outcomes.
ESRI 2004

22. Model Building
The ModelBuilder window consists of a display window in which you
build a diagram of your model, a Main menu, and a toolbar that you
can use to interact with elements in your model diagram. You can run
a model from within the ModelBuilder window or from its dialog box.
ESRI 2004

23. Project elements (blue ovals) exist prior to model
Tool to be executed (yellow rectangle)
Derived data (green ovals) produced by tool
Connector (arrow) showing sequence of processing
Value (light blue oval)
Derived value (light green oval)
ESRI 2004

24. Create A New Model
ESRI 2004

25. Model Building
ESRI 2004