University of Guelph Library

University of Guelph Library tag line "Changing Lives, Improving Life" (JPG 10kb)
Click the plus sign to expand this menu item (GIF 61 bytes)Click the minus sign to collapse this menu item (GIF 61 bytes)Geospatial Data Resources
Click the plus sign to expand this menu item (GIF 61 bytes)Click the minus sign to collapse this menu item (GIF 61 bytes)Help & Learning Resources

University of Guelph Library Ask Us! Service button and link to the initiative (PNG 6kb)

Data Resource Centre section title and link to its homepage (PNG – 11kb)

Merging Polygons using ArcGIS 3.x

Text Size: S M L XL

Go back one page (PNG 4 kb)

This page is designed to help you Merge Area Polygons in ArcView 3.x.

Why is it Necessary to Merge Polygons?

Digital Boundary/Cartographic Files contain one or more boundary polygons per geographic area. In the files we are using there are many areas that are comprised of several polygons (such as British Columbia, which includes Vancouver Island and the Queen Charlotte Islands and others). These parts were digitized separately and must be connected electronically. This is required for thematic mapping activities where data tables will be joined to the boundary theme table. Without merging, the mapping results can be misleading due to the way the data would be used for creating classification

Merging Area Polygons

  1. Open ArcView: from the start menu, scroll up to Programs, and look for a folder called ArcView version 3.1)
  2. Start with a New View and add the theme you wish to use in this example.

    Map 1 (JPG 17kb)

    Map 2 (JPG 9kb)

    Map 3 (JPG 24kb)

    When the theme is loaded, display it in ArcView by clicking on the box next to it.

  3. Click on the Province's name in the Table of Contents to make the theme active.

    Map 4 (JPG 26kb)

  4. Select Theme > Convert to Shapefile...
  5. Navigate to a folder where you'd like to save the theme.
  6. Enter a filename (provinces2.shp) in the Convert Provinces dialogue window. Click OK.

    Map 5 (JPG 21kb)

  7. Add the shapefile to View1 when asked. Click Yes.

    Map 6 (JPG 9kb)

  8. Click on the provinces2.shp theme name in the Table of Contents and make the theme active.

    Map 8 (JPG 27kb)

  9. Open the corresponding Attribute Table by selecting Theme > Table.
  10. Select the name of the geographic code on which the polygons will be "merged". Select Pruid and it will become highlighted.

    Map 9 (JPG 36kb)

  11. Select Field > Summarize.

    Map 10 (JPG 17kb)

  12. The Summary Table Definition dialogue box will open.
  13. Click the Save As... button and navigate to the folder where you'd like to save the file. Name the file Prov.dbf. Click OK. The Merge operation will create a new shape file with the name you provide.

    Map 11 (JPG 20kb)

  14. In the Field box, select Shape.
  15. In the Summarize By box, select Merge. Click the Add button.

    Map 12 (JPG 17kb)

  16. In the Field box, select Prename.
  17. In the Summarize By box, select First. Click the Add button.

    Map 13 (JPG 18kb)

  18. In the Field box, select Prfname.
  19. In the Summarize By box, select First. Click the Add button. Click OK when completed.

    Map 14 (JPG 19kb)

  20. Add to View1 When asked by clicking OK.

    Map 15 (JPG 12kb)

  21. Open Theme Table to see the Attributes of Prov Table and view the data in the new theme you created.

    Map 17 (JPG 82kb)

You'll notice that the new table is smaller and has only 14 fields compared to the other table. This is useful because it is now easier to select the themes in the View.

Go back one page (PNG 4 kb)

Top

Data Access

Contact

519–824–4120 ext. 56417

Visit

The DRC is located behind the Research Help desk in the McLaughlin Library.

Check DRC help hours

Last updated Auguast 16th, 2007 by M.G. (details)