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

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

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

Create A New Model ESRI 2004

Model Building ESRI 2004