[Qgis-user] Rendering shared exterior boundaries of adjacent polygon features

Thu Jun 20 00:56:15 PDT 2024

Hi Tim,

If I understood correctly what you want to do, I would suggest the following:

  1.  duplicate the layer
  2.  in the underlying layer, define rendering for area and the interior borders.
  3.  in the layer above, choose “merged features” and define the outer border lines as  e.g. “Outline: Simple line”

Is that what you intended to achieve?

Cheers,

Simon

Von: QGIS-User <qgis-user-bounces at lists.osgeo.org> Im Auftrag von Andreas Neumann via QGIS-User
Gesendet: Donnerstag, 20. Juni 2024 07:06
An: Tim Malloy <tim at tgmalloy.com>
Cc: qgis-user at lists.osgeo.org
Betreff: Re: [Qgis-user] Rendering shared exterior boundaries of adjacent polygon features

Hi Tim,

Are you looking for the "Draw line only inside polygon" feature described at http://nyalldawson.net/2014/01/qgis-two-neat-features-in-2-2/<http://atpscan.global.hornetsecurity.com/index.php?atp_str=RwVoBasBzp0qG5PBaIBa2ZTp_oSn-EMp-R-KBSZcJeFut-K8eHcQlLww1G4VFYTG5Y8mNsDd0gN4-95P7BLIv3b5m67DTIfIdDD2HA45DWEte8xJQw-ZRgIJ1vfiZ8S-_ktwIJTqccyQ_PqRF38YGw1uJD8ekB3xx65JNYviX1K8EYrlaYctljFUE1FNNekjuLnGgTtsK4eV9DUbGAh1w-qNdtlk2VWuX1sUG2xH8vJKcLKTOS5AlZWSR8fmNkKEV3q8Y9U__hO29kQsxLKABCP4nncACE8VKEIi901boiKmnbIhZ95apvOc2sft6CSpPbWjaDqK7auE7hhM1FDo2S3K9NJYNVS1xpUKbAiRbSXZt9OnIhwjOjojWsHtCQvz0TdwFxajIzo6I8ZgPo7yfZRyh_x2T1EFGZs> ?

In that case you would probably have two symbol levels:

- one for the line pattern fill (cross-hatched)

- a second one on top of the other one drawing an "Outline:simple line" on top of it using the "Draw line only inside polygon" checkbox.

This is only briefly described at https://docs.qgis.org/3.34/en/docs/user_manual/style_library/symbol_selector.html<https://atpscan.global.hornetsecurity.com/index.php?atp_str=y8OZvBGC5j6UVi3oVx8yVy3oQSO6v3Ln4xP7dL-3svwElbERB7-uCaAgUlrQk1OHiqjUFgMhvKryBIAlqrdnY1MIZClMAVCOv25egEPaWJtmlmKmhP3OM-S0ty98b5oJrGKyZmxC7zksiLwAR12vrry9a5T_nlV02DwmW5WLzBouOXxQa0b07bM0ccSl28hlbLVMJ7CjLQ3-jgyXpkPStj5IqVLzU-03Ny2WFg-3GcxoHG-ZsdG7IyzzEdvr4j5wp9H7GA1i363fqaF-7Zo0EPiSmN7Kal4u96Bdkh1rsK_xwcNdQy04gRvJnd7W4vFAeit06XlmrDC1zjcSXyaPLkLOYgmvLRL_J-esKXQfMH7eOvlQP1pj6GdOScxChNKOWToa4nwgSnRqbCM6OiMPJDG5Mfgn_xMkuf8jOjojcX14cXUvvrOAX8NDUQeYzg>

Quote:

Outline: simple line: uses a simple line symbol layer to represent the polygon boundary (Rings) which can be the interior rings only, the exterior ring only or all the rings). The Draw line only inside polygon option displays the polygon borders inside the polygon and can be useful to clearly represent adjacent polygon boundaries. The other settings for the outline simple line are the same as for simple line symbols.

But perhaps I am totally misunderstanding your request ...

Greetings,

Andreas

On 2024-06-20 03:26, Tim Malloy via QGIS-User wrote:

Fellow QGIS Users –

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).  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.  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.  I’m using QGIS 3.34.7 and my coding skills are limited.  I feel like I’ve seen this issue covered somewhere but have been unable to find a solution after extensive online exploration.

Method #1: “boundary( difference( $geometry, aggregate( 'union', 'intersects', $geometry, other_layer := @layer)))”  This expression was used on the outline component of the symbology described above.

Method #2: “CASE WHEN intersects( $geometry, geom_to_wkt( boundary( $geometry ))) THEN 0  ELSE 1 END”  Here I switched to using an expression on the stroke width of a simple fill, but I got an error message saying “Cannot convert to geometry”.

Any input would be greatly appreciated.

Tim

_______________________________________________
QGIS-User mailing list
QGIS-User at lists.osgeo.org<mailto:QGIS-User at lists.osgeo.org>
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user<https://atpscan.global.hornetsecurity.com/index.php?atp_str=ZXSEn2KfgzWL6HxBHsKplrZpRqDZa49QUtWmDlU_Zhc2eteHEWysv_Z3BbmTRpG4zzV9V8PJVIACXa_An3XRFo6NSNTLtdLQSnovEUkHVLcjmdmomNSiPGU9mnAibxrk6b2Ax0xf4zv16ENL4FslrPy3XbBV_46E4EfHfVxzuosea7IYFJvJqzXc43v4kJVt_P-EpfDCXR9e5fXRQe4acZrC0DJ_htWUKgS5ATcr6oNB_W2-bKKzSn55HXZ-ASg7dNUbHBHmynxWZ8Bu9huSGq2dIpL4QtTjn83xkphQmbmGCaVT_P_9ilnvBjbb8YmgkzycZQzHj4kHyOIqCYWSuuGOtEABq6WOy-qkIzo6I7xowcSpm0qPYSxCYyM6OiMDI_Q1kuI3s_sCqgNh2CgJ>
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user<https://atpscan.global.hornetsecurity.com/index.php?atp_str=bydwFP-WLCtHgLS29-vfjAd2iGzjs5vgPCOHpHkeymX4W5ZGFxr3Fv4Nb6eR_Sp0E_aM7YojowmTxEsFU3rREAxZWogSjKzYIp6uoNuuO2ETw0Rm25KVhypXAYwxJ9j84hIPxjfq6yNGlhXV-rBhTIUnNuqbxUA5GHHJ3Kgoekjxum-Nq0d2voyAzdRjhFwGs7Yi6Sc-WB6eWqslN60Lq7ziMcHyRbin-Yg9g3jSHZsq4X-TgDWvVr-Ealf-yvBF3icF5OagngAb_x7O9pEm6kZleM38tdM16fcKLjakvFyjLSVUrT5zljpKSOUHfpIqIWLB9nd1KhCzf8dk2H_w3Dk1rtFTZBdhvB9BIzo6Ixx2X_RyCLtA6lOIeSM6OiM7hsf0PlJJcsQgNBGZxkSo>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20240620/17fbbbad/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: WGS6S8BC1E
Type: image/png
Size: 8911 bytes
Desc: not available
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20240620/17fbbbad/attachment.png>