Monday, January 23, 2012

Join a spatial table with a non-graphical table in gvSIG

It is very useful to join a geospatial feature with a related non-graphical database table for analysis. This is a common feature found in commercial GIS applications like GeoMedia. I found a similar function in the open-source software gvSIG although it seems to handle only inner type joins. An example of using the gvSIG Join command is described below.
  1. Start gvSIG OADE. Load and display a geospatial feature e.g. States.shp in a map view.
     
  2. Load a database table e.g. SalesByStates.dbf.


  3. In the Map view legend TOC, click on the geospatial feature name e.g. States.shp. Then press the right button of the mouse on the name.

    A pop up menu appears.
  4. Choose Join.

    The Join tables dialog box appears.

  5. In the Field to join on combo box, choose a common field between the graphical and non-graphical table e.g. STATE_NAME.
  6. In the Field prefix field, type in the prefix string to indicate the fields from the geospatial feature table e.g. States_shp. Click Next.


  7. In the Name field, choose the non-graphical table e.g. SalesByStates.dbf.
  8. In the Field to join on, choose the common field between the non-graphical table and the feature table e.g. STATE_NAME.
  9. In the Field prefix field, type in the prefix string to indicate the fields from the non-graphical table e.g. SalesByStates_dbf. Click Finish.



    The tables are joined.
To see the results of the join, you can view the attribute table or query the attributes of selected features. For example, press CTRL+I, then click on any feature in the map view. The Query results dialog box should appear showing the joined table attributes, as shown below.


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