Okay, so I have 2 shapefiles:

  • US states outline file (very coarse/simple outlines)
  • Global Self-consistent Hierarchical High-resolution Shorelines, Level F (much finer spatial resolution)

I am trying to make a map series for my employer using the GSHHS as my land/not land background, and overlaying the state outlines over top. I have other layers, but they're not relevant to this discussion.

This is what the smallest North America polygon looks like.
map of both files overlain
I am only interested in the western US, and only need a couple hundred miles into Mexico and Canada for background purposes.
I can't simply clip for obvious reasons, and there's another problem...
Case 1 large-scale image of the problem
Case 2 enter image description here
In both cases, the GCHHS runs inside as well as outside the rough state lines. I'd like to update the shoreline of the state file to match the GCHHS.
The only theoretical way I've come up with would be to do an Erase of the GCHHS based on the states, which would give me the bits outside the states, then maybe a Clip of the states based on the GCHHS to get the bits where the states overrun.
And once I get all these slivers, I'd have to dissolve them all into the proper state.

Should I just start looking for higher-resolution state polygons?
Thanks for any ideas or suggestions.

  • 2
    This is a really great question (not to discourage your efforst), but there certainly are much better state polys available. My experience with Maryland at least, the State Highway Administartion (SHA) had some great high-res files available.
    – Roy
    Jun 7, 2012 at 18:25

1 Answer 1


I assume that you want to reconcile the crude statelines with the GSHHS data. If your licence allows you to use the Integrate Tool, there is a relatively simple solution:

Massively buffer your statelines, but obviously don't dissolve. Then use ArcMap's Integrate tool to integrate the buffered statelines with itself. This will put back all the internal boundaries (albeit with lots of extra vertices now). You should now have a statelines dataset that has all the internal lines where they ought to be but the coastline extends far out to sea. Now do your clip operation and you will be left with a statelines boundary set that exactly matches the GSHHS polygons.

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