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List: qgis-user
Subject: Re: [Qgis-user] Problem Noticed with QGIS
From: Richard McDonnell via Qgis-user <qgis-user () lists ! osgeo ! org>
Date: 2022-11-29 16:58:18
Message-ID: 7444a673609e4e5186e09b08cba3dab5 () opw ! ie
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Andrea,
Thank you for the clarification and the work around!
Regards,
Richard
——
Richard McDonnell MSc GIS, FME Certified Professional
FRM Data Management
——
Oifig na nOibreacha Poiblí
Office of Public Works
Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36
Jonathan Swift Street, Trim, Co Meath, C15 NX36
——
M +353 87 688 5964 T +353 46 942 2409
https://gov.ie/opw
——
To send me files larger than 30MB, please use the link below \
https://filetransfer.opw.ie/filedrop/richard.mcdonnell@opw.ie
Email Disclaimer: https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/
——
MSc GIS, FME Certified Professional
——
Oifig na nOibreacha Poiblí
Office of Public Works
Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36
Jonathan Swift Street, Trim, Co Meath, C15 NX36
——
M +353 87 688 5964 T +353 46 942 2409
https://https://gov.ie/opw<https://www.opw.ie>
——
Email Disclaimer: https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/<https://www.opw.ie/en/disclaimer/>
From: Qgis-user <qgis-user-bounces@lists.osgeo.org> On Behalf Of Andrea Giudiceandrea \
via Qgis-user
Sent: 29 November 2022 16:14
To: qgis-user@lists.osgeo.org
Subject: Re: [Qgis-user] Problem Noticed with QGIS
Richard McDonnell richard.mcdonnell at \
opw.ie<mailto:qgis-user%40lists.osgeo.org?Subject=Re%3A%20%5BQgis-user%5D%20Problem%20 \
Noticed%20with%20QGIS&In-Reply-To=%3C9708d6dac99943929281a173e54a9e6f%40opw.ie%3E> \
Tue Nov 29 07:17:48 PST 2022 ________________________________
1. If I use the option [Create temporary Layer] it produces a Singlepart \
Geometry as Expected, If I save the output to a File, the resultant geometry is \
stated as Polygon (MultiPolygon) Its the same for Linestrings also.
Hi Richard,
as explained (also by me) in the linked issue report [1], the line (PolyLine) and \
polygon (Polygon) ESRI Shapefile layer types are actually multi-part layer types \
which can store both multi-part geometries with only one part and multi-part \
geometries with more than one part. Only the point layer type has two different ESRI \
Shapefile layer types: the ESRI Shapefile Point type (which is a single-part type and \
can store only single-part geometries) and the ESRI Shapefile MultiPoint type (which \
is a multi-part type and can store multi-part geometries both with only one part and \
with more than one part).
Please see the ESRI Shapefile Technical Description [2].
If you want to check that a line (PolyLine) and polygon (Polygon) ESRI Shapefile \
layer imported in QGIS contains features with only 1 part, you need to check the \
number of part for each feature, for example using the num_geometries function [3] in \
the field calculator.
Best regards.
Andrea Giudiceandrea
[1] https://github.com/qgis/QGIS/issues/50720
[2] https://www.esri.com/Library/Whitepapers/Pdfs/Shapefile.pdf/
[3] https://docs.qgis.org/3.22/en/docs/user_manual/expressions/functions_list.html#num-geometries
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<p class="MsoNormal"><span \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Andrea,<o:p></o:p></span></p>
<p class="MsoNormal"><span \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Thank \
you for the clarification and the work around!<o:p></o:p></span></p> <p \
class="MsoNormal"><span \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Regards,<br>
<br>
Richard<o:p></o:p></span></p>
<p class="MsoNormal"><span \
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span \
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<td style="FONT-SIZE: 9pt; FONT-FAMILY: Arial,sans-serif; WIDTH: 500px; COLOR: \
#004d44; PADDING-BOTTOM: 6px"> <span style="FONT-FAMILY: Arial, sans-serif; \
FONT-WEIGHT: bold; COLOR: #004d44"><br> ——</span><br>
<span style="FONT-FAMILY: Arial, sans-serif; FONT-WEIGHT: bold; COLOR: \
#004d44">Richard McDonnell MSc GIS, FME Certified Professional</span><br> <span \
style="FONT-FAMILY: Arial, sans-serif; COLOR: #004d44"><i>FRM Data \
Management</i></span><br> <br>
<span style="FONT-FAMILY: Arial, sans-serif; COLOR: #004d44">——</span><br>
<span style="FONT-FAMILY: Arial, sans-serif; FONT-WEIGHT: bold; COLOR: #004d44">Oifig \
na nOibreacha Poiblí</span><br> <span style="FONT-FAMILY: Arial, sans-serif; COLOR: \
#004d44">Office of Public Works</span><br> <br>
<span style="FONT-FAMILY: Arial, sans-serif; FONT-WEIGHT: bold; COLOR: \
#565148">Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36 </span><br>
<span style="FONT-FAMILY: Arial, sans-serif; COLOR: #565148">Jonathan Swift Street, \
Trim, Co Meath, C15 NX36</span><br> <span style="FONT-FAMILY: Arial, sans-serif; \
COLOR: #565148">——</span><br> <span style="FONT-FAMILY: Arial, sans-serif; COLOR: \
#565148">M +353 87 688 5964 T +353 46 942 2409</span><br> <a \
href="https://gov.ie/opw">https://gov.ie/opw</a><br> <br>
<span style="FONT-FAMILY: Arial, sans-serif; COLOR: #004d44">——<br>
To send me files larger than 30MB, please use the link below \
https://filetransfer.opw.ie/filedrop/richard.mcdonnell@opw.ie<br> </span><br>
<span style="FONT-FAMILY: Arial, sans-serif; COLOR: #004d44">Email Disclaimer: \
https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/ </span></td>
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FONT-WEIGHT: bold; COLOR: #004d44"><br> ——</span><br>
<span style="FONT-FAMILY: Arial, sans-serif; FONT-WEIGHT: bold; COLOR: #004d44">MSc \
GIS, FME Certified Professional</span><br> <br>
<span style="FONT-FAMILY: Arial, sans-serif; COLOR: #004d44">——</span><br>
<span style="FONT-FAMILY: Arial, sans-serif; FONT-WEIGHT: bold; COLOR: #004d44">Oifig \
na nOibreacha Poiblí</span><br> <span style="FONT-FAMILY: Arial, sans-serif; COLOR: \
#004d44">Office of Public Works</span><br> <br>
<span style="FONT-FAMILY: Arial, sans-serif; FONT-WEIGHT: bold; COLOR: \
#565148">Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36 </span><br>
<span style="FONT-FAMILY: Arial, sans-serif; COLOR: #565148">Jonathan Swift Street, \
Trim, Co Meath, C15 NX36</span><br> <span style="FONT-FAMILY: Arial, sans-serif; \
COLOR: #565148">——</span><br> <span style="FONT-FAMILY: Arial, sans-serif; COLOR: \
#565148">M +353 87 688 5964 T +353 46 942 2409</span><br> <font \
color="#565148"><a href="https://www.opw.ie">https://https://gov.ie/opw</a></font><br>
<br>
<span style="FONT-FAMILY: Arial, sans-serif; COLOR: #004d44">——<br>
</span><span style="FONT-FAMILY: Arial, sans-serif; COLOR: #004d44">Email Disclaimer:
<a href="https://www.opw.ie/en/disclaimer/">https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/</a></span>
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<p class="MsoNormal"><b><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span \
lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> \
Qgis-user <qgis-user-bounces@lists.osgeo.org> <b>On Behalf Of </b>Andrea \
Giudiceandrea via Qgis-user<br> <b>Sent:</b> 29 November 2022 16:14<br>
<b>To:</b> qgis-user@lists.osgeo.org<br>
<b>Subject:</b> Re: [Qgis-user] Problem Noticed with QGIS<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><b><span style="font-size:13.5pt;color:black">Richard \
McDonnell</span></b><span style="color:black"> </span><a \
href="mailto:qgis-user%40lists.osgeo.org?Subject=Re%3A%20%5BQgis-user%5D%20Problem%20N \
oticed%20with%20QGIS&In-Reply-To=%3C9708d6dac99943929281a173e54a9e6f%40opw.ie%3E" \
title="[Qgis-user] Problem Noticed with QGIS"><span \
style="font-size:13.5pt">richard.mcdonnell at opw.ie</span></a><span \
style="font-size:13.5pt;color:black"><br> </span><i><span style="color:black">Tue Nov \
29 07:17:48 PST 2022</span></i> <o:p> </o:p></p>
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<pre style="white-space:pre-wrap;font-variant-ligatures: normal;font-variant-caps: \
normal;orphans: 2;text-align:start;widows: 2;-webkit-text-stroke-width: \
0px;text-decoration-thickness: initial;text-decoration-style: \
initial;text-decoration-color: initial;word-spacing:0px"><span \
style="color:black">1. If I use the option \
[Create temporary Layer] it produces a Singlepart Geometry as Expected, If I save the \
output to a File, the resultant geometry is stated as Polygon (MultiPolygon) Its the \
same for Linestrings also.<o:p></o:p></span></pre> </blockquote>
<p class="MsoNormal"><br>
Hi Richard,<br>
as explained (also by me) in the linked issue report [1], the line (PolyLine) and \
polygon (Polygon) ESRI Shapefile layer types are actually multi-part layer types \
which can store both multi-part geometries with only one part and multi-part \
geometries with more than one part.<br>
Only the point layer type has two different ESRI Shapefile layer types: the ESRI \
Shapefile Point type (which is a single-part type and can store only single-part \
geometries) and the ESRI Shapefile MultiPoint type (which is a multi-part type and \
can store multi-part geometries both with only one part and with more than one \
part).<br> <br>
Please see the ESRI Shapefile Technical Description [2].<br>
<br>
If you want to check that a line (PolyLine) and polygon (Polygon) ESRI Shapefile \
layer imported in QGIS contains features with only 1 part, you need to check the \
number of part for each feature, for example using the num_geometries function [3] in \
the field calculator.<br>
<br>
Best regards.<br>
<br>
Andrea Giudiceandrea<br>
<br>
[1] <a href="https://github.com/qgis/QGIS/issues/50720">https://github.com/qgis/QGIS/issues/50720</a><br>
[2] <a href="https://www.esri.com/Library/Whitepapers/Pdfs/Shapefile.pdf/">https://www.esri.com/Library/Whitepapers/Pdfs/Shapefile.pdf/</a><br>
[3] <a href="https://docs.qgis.org/3.22/en/docs/user_manual/expressions/functions_list.html#num-geometries">
https://docs.qgis.org/3.22/en/docs/user_manual/expressions/functions_list.html#num-geometries</a>
<o:p></o:p></p>
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