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Joining Polygon Boundaries Using Symbol Levels

JoshuaDamron

Working with a road polygon layer I want to use the Join property/check box in Symbol Levels (http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Dissolving_polygon_boundaries_using_symbol_level_drawing/00s500000025000000/) to remove the outlines between like road polygons.

In my buildings polygon layer when I open the symbol level window everything is fine and I have the check boxes available to me (see below)

[ATTACH=CONFIG]21623[/ATTACH]

However, in my roads ploy the symbol level join property is greyed out and unavailable (see below.

[ATTACH=CONFIG]21624[/ATTACH]

Both layers are feature classes in file geodatabases. At first I thought it was due to my layer groupings, but I ungrouped my layers and I am still having this issue. I also tried symbolizing my roads as a single layer (no categories) and this did not work either.

What could the difference be in symbolizing these two layers? Any & all ideas are appreciated.

Symbolevels_Check.jpg

SymbLevelNo Check.jpg

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Accepted answers

DavidBarnes

See in the Symbol Property Editor in your second screenshot, where it shows the symbol's layers in the lower left? That's what I meant by drawing each layer. If you have Join checked on it will draw one symbol layer for all features using that symbol, then it will draw the other symbol layer for all features. The dissolve example in the help draws the outlines first and then draws the fill on top. That covers up the outlines. They're still there, you just don't see them because they are covered.

I expect the Parking_Public and Bridge symbols in your roads layer are single layer symbols. If you look at the Symbol Property Editor for those I would expect to see only a single layer in the Layers pane in the lower left of that dialog.

Are you trying to dissolve the interior lines for each type while still keeping the outline around the entire type? If so, it will only do that for features that actually touch each other, and the fill needs to be a solid color so it can cover the lines. I can't tell if your feature classes, like Freeway and "all other values", have a white fill or no fill/no color.

All comments

DavidBarnes

I think it has to do with the type of symbol. As you may know, symbols can be pretty simple or they can be made with more than one symbol combined in layers. For example, I suspect the fill in your first picture is made of a fill and a separate outline. The fill in the second picture is probably a fill and outline combined. If you look in the symbol editor you should be able to confirm this. In the lower left corner of that dialog you can see how many layers of symbols make up the combined symbol. I think the join option works by drawing the symbol layers in a different order from the default (by symbol layers, rather than feature by feature). I hope that helps!

Anonymous User

Original User: HealdsburgCA

David,

Thank you for the quick post back. I'm not sure what exactly you mean by drawing with "symbol layers vs feature by feature" but do I think you are on to something... its not the feature classes or layers so much as the symbols selected for each subtype. As I trouble shoot the issue it�??s a bit convoluted. I�??m sure there�??s logic somewhere but I�??m not seeing it yet.

Firstly, even when I get a symbol to allow me to join, it doesn�??t seem to necessarily work, meaning that as I understand it Joins are supposed to visually dissolve outlines between like symbol categories (see purple arrow/highlights in attached image #1)

[ATTACH=CONFIG]21644[/ATTACH]
Image #1

Secondly, I started selecting random symbols from the many styles available and found that some will allow a join/merge and others won�??t. However, I don�??t really see any consistency in what defines success or failure. At first I thought that it was layering multiple symbols in the Symbol Property Editor (See Image #2). However, as you can see by the symbols in Image #1 this did not hold true. You can see hatch symbols built from multiple layers allowing Joins while simpler symbols do not.

[ATTACH=CONFIG]21643[/ATTACH]
Image #2

In Image#1 I have red arrows pointing to the orange �??Paved_Road�?� and hollow �??Freeway�?�, this is because I created the freeway symbol by add Value> Freeway then grouping Freeway to Paved_Road and ungrouping them, then changing the symbology ofFreeway to a simple outline. As you can see Joins are permitted in both.

In Image #1 I have orange arrows pointing to the hollow �?�Parking_Public�?� and blue �??Bridge�?�, this is to show that I created the Parking_Public symbol by add Value> Parking_Public then grouping Parking Public to Bridge and ungrouping them, then changing the symbology for Parking_Public to just a simple outline. As you can see Joins are not permitted in either of them.

The truly odd thing to me is that I selected the exact same style symobology for the outlines in both Freeway & Parking Public with two different results..

Do you or anyone else have any insights into these aparent inconsistancies?

Original User: HealdsburgCA

If you have Join checked on it will draw one symbol layer for all features using that symbol, then it will draw the other symbol layer for all features. The dissolve example in the help draws the outlines first and then draws the fill on top. That covers up the outlines. They're still there, you just don't see them because they are covered.

You are right! I get it! I could have saved a bunch of trouble if I'd slowed down and read the Help line by line... Thank you for your patience...

[ATTACH=CONFIG]21703[/ATTACH]

So to get the Join/Merge check boxes to show up the symbology must be composed of more than one layer. To get a dissolve the boundaries must be drawn with the lower layer.

I found that I had to check both Join & Merge... I see that Merge "dissolved" the layers by taking the topmost symbol layer and covering the lower symbol layers. Not that it really matters but I'm not 100% clear on what the Join part did except for make the Merge Check box available.

Now that I get it I'll definitly be using this feature more often. Thank you again for your help!

Arc_Fill on top.jpg

DavidBarnes

Glad I could help. 🙂

I think what it does is Join is applied to the features within the class, while Merge is applied between 2 or more classes (all classes that have the Merge checkbox checked on).

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