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    Hi,<br>
    Also for clarification:<br>
    Being a County layer, I would not expect overlapping polygons.<br>
    My take is that Tim means "concurrent exterior boundaries" and not "<span
style="font-size:12pt;font-family:"Century Gothic",sans-serif">overlapping
      exterior boundaries</span>"<br>
    <br>
    <b>Tim: </b>What is the reason for wanting only one of the
    concurrent(?) boundaries rendered?<br>
    Maybe there are other ways to do what you want to.<br>
    <br>
    HTH,<br>
    Zoltan<br>
    <br>
    <br>
    <div class="moz-cite-prefix">On 2024/06/20 07:46, Emma Hain via
      QGIS-User wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CACGKw0YUxt4nKC+zD13kfLmbohZ4uN_q=d=idURj0p=UgQWBPw@mail.gmail.com">
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        <div>Hi Tim</div>
        <div>So let's see if I understand you. </div>
        <div>- There are 2 polygon layers (green and black)<br>
        </div>
        <div>- These polygon layers sometime overlap</div>
        <div>- You wish to show only on the pink line in the below image
          and not the green overlapping part?<br>
        </div>
        <div><img src="cid:part1.7BYfzw4G.k1AOv80S@geograph.co.za"
            alt="image.png" class="" width="578" height="473"><br>
          <br>
        </div>
      </div>
      <br>
      <div class="gmail_quote">
        <div dir="ltr" class="gmail_attr">On Thu, 20 Jun 2024 at 11:26,
          Tim Malloy via QGIS-User <<a
            href="mailto:qgis-user@lists.osgeo.org"
            moz-do-not-send="true" class="moz-txt-link-freetext">qgis-user@lists.osgeo.org</a>>
          wrote:<br>
        </div>
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style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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                <p class="MsoNormal"><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif">Fellow
                    QGIS Users –</span></p>
                <p class="MsoNormal"><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif"> </span></p>
                <p class="MsoNormal"><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif">I’m
                    trying to determine if its possible to have QGIS
                    render the exterior boundary of polygon features
                    only once when that boundary is shared with an
                    adjacent feature (don’t render overlapping exterior
                    boundaries for both polygon features).<span> 
                    </span>The data I’m working with is a county parcels
                    layer and the symbology I’m using for this layer is
                    a cross hatched line fill with a separate component
                    for the outline of the polygons.<span> 
                    </span>I’ve tried a couple of expressions (examples
                    below) including one geometry generator and one data
                    defined override for the stroke width of the
                    boundary line but none of them achieves my
                    objective.<span> 
                    </span>I’m using QGIS <span
                      class="m_1254814045772383059GramE">3.34.7</span>
                    and my coding skills are limited.<span> 
                    </span>I feel like I’ve seen this issue covered
                    somewhere but have been unable to find a solution
                    after extensive online exploration.<span> 
                    </span></span></p>
                <p class="MsoNormal"><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif"> </span></p>
                <p class="MsoNormal" style="text-indent:0.5in"><b><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif">Method
                      #1:<span> 
                      </span>“</span></b><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif">boundary(
                    difference( $geometry, aggregate( 'union',
                    'intersects', $geometry, other_layer := @layer)))”<span> 
                    </span>This expression was used on the outline
                    component of the symbology described above.<span> 
                    </span></span></p>
                <p class="MsoNormal"><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif"> </span></p>
                <p class="MsoNormal" style="margin-left:1in"><b><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif">Method
                      #2:<span> 
                      </span></span></b><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif">“CASE
                    WHEN intersects( $geometry, geom_to_wkt( boundary(
                    $geometry ))) THEN 0
                    <span> </span>ELSE 1 END”<span> 
                    </span>Here I switched to using an expression on the
                    stroke width of a simple fill, but I got an error
                    message
                    <span class="m_1254814045772383059GramE">saying</span>
                    “Cannot convert to geometry”.<span> 
                    </span></span></p>
                <p class="MsoNormal" style="margin-left:1in"><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif"> </span></p>
                <p class="MsoNormal" style="margin-left:1in"><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif">Any
                    input would be greatly appreciated.</span></p>
                <p class="MsoNormal" style="margin-left:1in"><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif"> </span></p>
                <p class="MsoNormal" style="margin-left:1in"><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif">Tim</span></p>
                <p class="MsoNormal"><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif"> </span></p>
                <p class="MsoNormal"><span
style="font-size:12pt;font-family:"Century Gothic",sans-serif"> </span></p>
              </div>
            </div>
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      <span class="gmail_signature_prefix">-- </span><br>
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          <div
style="margin-bottom:20px;font-family:verdana,sans-serif;color:rgb(68,68,68)">Emma
            Hain — Product Manager/Senior GIS Analyst<br>
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      <pre class="moz-quote-pre" wrap="">_______________________________________________
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</pre>
    </blockquote>
    <br>
    <pre class="moz-signature" cols="72">-- 

=============================================
Zoltan Szecsei GPrGISc 0031
Director, Geograph (Pty) Ltd.
GIS and Photogrammetric Services

Cape Town, South Africa.

Mobile: +27-83-6004028 (Signal, not WhatsApp)
        +974-5058-8729 
        +36-20-4808362

<a class="moz-txt-link-abbreviated" href="http://www.geograph.co.za">www.geograph.co.za</a>
=============================================</pre>
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