Grouping Polygons for Display Only

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05-22-2012 11:47 AM
SeanGambrel
Occasional Contributor II
Hi all, Hopefully a simple question for you.  I'm using ArcInfo 9.31.
 
I have a polygon feature class of watersheds which have been divided up into subwatersheds.  So the base feature is a tributary to one of a number of larger streams in town.  The features all include a field for a "primary watershed" - basically allowing us to group the subatersheds into one stream's overall watershed.

So the question is this:  How do I DISPLAY just the outline of the larger, primary watersheds, without showing the boundaries of the subwatersheds inside? 

I need a solution that is just a display setting for producing maps, which deosn't involve editing or geoprocessing the data.  Both the original watersheds (divided to subwatershed) and the grouped watersheds (primary watersheds) will continue to be used into the future, for maps and for general GIS use.  We also expect these watershed boundaries to change in the near future as we collect more information, so I really don't want to have to try to keep two parallel datasets - one if primary watersheds and one of subwatersheds - geometrically identical.

Can it be done?  Perhaps with a Representation???


Thank you for your time!
Sean
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5 Replies
TimHopper
Regular Contributor
Sean,

I'm not aware of any functionality which would allow you to achieve this goal without dissolving or merging your dataset.

I know that there isn't any functionality included with cartographic representations that would give you the output you desire.  Representation symbology works just like standard symbology with polygons.  The symbol draws to the edge of the polygon; if the larger (dissolved) polygon isn't in the data, it can't be used for display purposes.

Sorry to be the messenger...
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TimHopper
Regular Contributor
Very nice.
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SeanGambrel
Occasional Contributor II
Awesome!  Symbol Levels!  I knew there must be a way to do this...

So a troubleshooting question:  I need to use the join/merge rules, but for some reason the check boxes do not appear in the dialog.  Any reason what might cause this?

Thanks!!
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SeanGambrel
Occasional Contributor II
Thanks, that does make sense.... 

I initially just had an outline symbol so I didn't do the multi-level symbol as outlined in the help.  I've gone back through, step-by-step, and now I am getting mixed results.  If I specify a fill color for the top symbol, then the joining works perfectly and I get essentially the desired result.  If I specify a "no color" fill for the top symbol, the  symbology reverts back to the default where there is no joining and al lthe boundaries show.  Any thought on this?

I'll continue trying different variables and see if I can get it to work.  Thanks agian for taking the time to help me out!
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SeanGambrel
Occasional Contributor II
Thanks, that makes much more sense now. 

Yes, we want these shown as just boundaries with other data "underneath".  I'll try your suggestion, but it might not work out in this aprticular case.

For what its worth, I spent a bunch of time researching representations and if it would be possible via that route.  The "Cut" geometric tool seemed the most promising, but I couldn't quite get it working right.

As before, if I do find a solution, I'll be sure to post it!

Thanks again,
Sean
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