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

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

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.

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

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

Extract: Polygon Clipping

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

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

Union Attributes tables contain different data

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

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

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.

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

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.