1. GIS Institute Center for Geographic Analysis
Spatial Structures in the Social Sciences
GIS Institute Center for Geographic Analysis
Transformation of Vectors/ Feature data
Global Positioning Systems

2. Spatial Structures in the Social Sciences
Geoprocessing
GIS operation used to manipulate spatial data.
A typical geoprocessing operation takes an input dataset, performs an operation on that dataset, and returns the result of the operation as an output dataset.
INPUT
OUTPUT
Typically take input data set(s), manipulate, and produce output data sets
OPERATION
TOOL
Global Positioning Systems

3. Geoprocessing in ArcGIS
ArcToolBox (tools for performing analysis and managing geographic data)
A geoprocessing tool performs a operation on a geographic dataset:
creating a buffer zone around features.
adding a field to a table.
projecting a dataset from one map projection to another.
ArcGIS includes hundreds geoprocessing tools.
Now, let’s talk about GEOPROCESSING in ARCGIS
ArcGIS provides a geoprocessing tools for performing analysis and managing your geographic data.
A single geoprocessing tool performs a operation on geographic data (creating a buffer zone around features, adding a field to a table, projecting a dataset from one map projection to another).
ArcGIS includes hundreds of geoprocessing tools.

4. Spatial Structures in the Social Sciences
Geoprocessing Tools
Extract:
Select
Clip
Proximity:
Buffer
Overlay:
Union
Intersect
EXTRACT:
GIS datasets often contain more data than you need. The Extract tools let you select features and attributes in a feature class or table based on a query (SQL expression) or spatial extraction. The output features and attributes are stored in a feature class or table.
PROXIMITY:
One of the most basic questions asked of a GIS is "what's near what?" For example:
What is the distance between two locations?
OVERLAY:
One of the most basic questions asked of a GIS is "What's on top of what?" For example:
What wells are within a specific area?
Global Positioning Systems

5. Extract: Line (Arc) Clipping
Spatial Structures in the Social Sciences
Extract: Line (Arc) Clipping
Input layer - Streets
Clip layer – Central Business District (selected)
Output layer - Streets within Central Business District
EXTRACT:
GIS datasets often contain more data than you need. The Extract tools let you select features and attributes in a feature class or table based on a query (SQL expression) or spatial extraction. The output features and attributes are stored in a feature class or table.
Global Positioning Systems

6. Extract: Polygon Clipping

7. Spatial Structures in the Social Sciences
Proximity: Buffering
Point
Polyline
Polygon
PROXIMITY:
One of the most basic questions asked of a GIS is "what's near what?" For example:
What is the distance between two locations?
Global Positioning Systems

9. Spatial Structures in the Social Sciences
Union
Spatial Structures in the Social Sciences
Topological overlay of two polygonal spatial datasets that preserves features that
fall within the spatial extent of either input dataset (Pittsburgh ZIP codes and
neighborhoods.
Global Positioning Systems

10. Union
Attributes tables contain different data

11. Result: Polygons with information from both layers
Union
Result: Polygons with information from both layers

12. Polygon Overlay (Union) : Spurious or sliver polygons
In this example, two polygons are overlaid to form 9 new polygons. One is formed from both input polygons; four are formed by Polygon A and not Polygon B; and four are formed by Polygon B and not Polygon A.
As a result large numbers of small sliver polygons will be created B A

13. Intersect
Use Intersect when you want to overlay a layer (point/line/poly) with the polygons in another layer so that the resulting output layer:
It has the combined attribute data of the features in the two inputs
It only contains features that fall within the spatial extent of the overlay polygons.

15. At the end of the Vector lab you should be able to
Spatial Structures in the Social Sciences
At the end of the Vector lab you should be able to
Work with one spatial layer to
Clip and Select from a spatial dataset
Create a Buffer
Work with multiple polygon layers to overlay
Intersect
Union
Use location or attribute queries from the previous lab
Global Positioning Systems

16. Selecting and Clipping: Extract Massachusetts tracts.
Buffering: Create 1 miles buffer zone from Massachusetts Hospitals and estimate the population living in these buffers around Hospitals (assuming the population is uniformly distributed)
Intersecting: Tracts and buffer zone and calculate a new area to estimate the population with this area.
Union: Tracts and buffer zone.