Take the 2-minute tour ×
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.

I intend to convert a raster to several polygons, but I want to ignore too small polygons, and just keep larger polygon. How can I do that? Thanks in advance!

share|improve this question

1 Answer 1

up vote 4 down vote accepted

There are several approaches you may take. The first involves the Raster to Polygon tool itself. Make sure to check the "Simplify polygons" checkbox--this will greatly reduce the number of small polygons. If there are still too many sliver polygons, use the Eliminate (Data Management) tool. Eliminate works by merging smaller polygons with larger polygons. You can specify an expression in the SQL window to further reduce the sliver polygons (e.g. "Area_Sq_Miles" < 0.15).

Edit:

If you are having difficulty dialing in the Eliminate SQL expression, try selecting the polygons you would like to remove directly in the attribute table:

  1. Right click on layer select Open Attribute Table
  2. Select the "Select by Attributes" tab
  3. Create an expression similar to: "Shape_Area" < 7856 select "apply"
  4. Start the Editor
  5. Right click on the highlighted attributes and select "Delete"
  6. If you do not like the results, stop editing and do not save your results.
share|improve this answer
    
I tried to use eliminate by the query (Area > 50000000 square meter), and it did eliminate some, but it still contains some small polygons. Is it possible to just keep 2 or 3 polygon? –  Vicky Oct 17 '12 at 21:30
    
@Vicky Yan-ting Liau Post edited to address comments. Also, you can run "Eliminate" multiple times. –  Aaron Oct 17 '12 at 21:50

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.