I have a zip code map which I added per zip code data too (a regional director for each zipcode), and then dissolved the map based on the director attribute. As you may or may not know, zip codes are really just postal routes, so areas in the U.S. that do not receive post, do not have zipcodes. Because of this, there are empty spaces on my map I want to fill.

So my question is, can I somehow merge my dissolved zip code map with a map of the US state boundaries, and use that to fill the empty spaces? I guess I could manually draw out the polygons to fill the gaps, but this would be incredibly time consuming.

Here is a snapshot of Maine to show what I'm explaining. Cyan is zipcode vector, grey is US state boundaries.

Any ideas?

  • Could you explain why you want to alter your data to fill empty spaces? What is the purpose of that? – whuber Sep 29 '14 at 20:32
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    I've done this in ArcMap by overlaying the complete US State polygons with my ZIP code polygons, deleting the ZIP code polygons to have only the remaining missing pieces. Then merging the two together – Maksim Sep 29 '14 at 20:33
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    @whuber It is because I am actually using this map for an interactive piece in Javascript. I need the empty spaces to be filled so the map looks clean and like the full US. – PStokes Sep 29 '14 at 20:40
  • @Maksim I think that is my best bet. I should be able to replicate that process with Symmetrical Difference and Merge Shapefiles in QGIS. – PStokes Sep 29 '14 at 20:43
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    Would it be problematic to fill the empty spaces with a single (admittedly rather complicated) polygon to represent them? Or even to just use a polygon of the full US as a backdrop? – whuber Sep 29 '14 at 20:46

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