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Importing an Esri Shapefile

Revision as of 14:00, 25 March 2012 by Judyvdouglas.verizon.net (Talk | contribs) (Using the Shapefile Graph Generator)

The Esri Shapefile Format

The Esri shapefile is a popular format for geographic information systems (GIS). Shapefiles can describe polygons, polylines and points. For example, polygons can represent geographical regions like countries and states while polylines can represent roads, rivers and so on. Points are currently not used used in the Shapefile Graph Generator.

A shapefile is a set of various files: three of these files are used by the Shapefile Graph Generator.

  • .shp — shape format; contains the shapes (polygons, polylines and points)
  • .prj — projection format; contains the coordinate system and projection information
  • .dbf — attribute format; contains attributes for each shape

Using the Shapefile Graph Generator

The Shapefile Graph Generator can read polygons and polylines from shapefiles. Polygons are imported as geographical regions while polylines can be processed to create different kinds of edges. If a shapefile contains a road network, the polylines could be used to create Road Transportation Edges.

The shapefiles used in this example can be downloaded from [1]. The UI for importing shapefiles can be displayed by choosing the item Shapefile Graph Generator in the New Graph wizard. Click on Select Shape Files to select multiple shapefiles in a file dialog. For each of the shapefiles, you must specify if the file contains regions, roads or polylines with migration data. Also you need to specify a unique ID for each shape by selecting an ID column in the related combo box. The data of all columns can be displayed by clicking on Show Data. If the shapefile contains roads or polylines with migration data, additional parameters like Road Class, Migration Rate and so on must be specified. To do so, either use the data from a table column or enter the value for the parameter in the text field. In the latter case, the same value is used for all shapes.

In the images below one can see an example on how to use the GUI. First PolbndA.shp is selected, the type is set to Regions and gfid is used as Region ID. Then RailrdL.shp is selected, the type is set to Roads, gfid is used as Road ID and the Road Class is set to Railroad.

Running the Shapefile Graph Generator as shown above, the result should look like this in the Graph Editor.