<div dir="ltr">You can run the 'Check Validity' tool from the Processing Toolbox with 'QGIS' method and it will point out the error. (<a href="https://imgur.com/a/yIP947p">see screenshot</a>) 'line 1 contains 3 duplicate nodes starting at vertex 13'. So QGIS will try to fix this by creating a multipart geometry.<br clear="all"><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div></div><div><table cellpadding="0" cellspacing="0" style="border-spacing:0px;border-collapse:collapse;color:rgb(68,68,68);width:480px;font-size:10pt;font-family:Arial,sans-serif;line-height:normal"><tbody><tr><td valign="top" style="padding:10px 0px 12px;width:160px;vertical-align:top"><a href="https://spatialthoughts.com/" style="background-color:transparent;color:rgb(51,122,183)" target="_blank"><img border="0" alt="Logo" width="141" src="https://spatialthoughts685850346.files.wordpress.com/2019/12/spatial_thoughts_logo.png" style="border:0px;vertical-align:middle;width:141px;height:auto"></a></td><td style="padding:6px 0px;width:320px"><table cellpadding="0" cellspacing="0" style="border-spacing:0px;border-collapse:collapse;background-color:transparent"><tbody><tr><td style="padding:0px;font-size:12pt;font-family:Arial,sans-serif;font-weight:bold;color:rgb(61,60,63)"><span style="color:rgb(0,175,239)">Ujaval Gandhi</span></td></tr><tr><td style="padding:0px 0px 11px;font-size:10pt;font-family:Arial,sans-serif;color:rgb(61,60,63)"><span style="color:rgb(0,175,239)">Spatial Thoughts</span></td></tr><tr><td style="padding:0px;font-size:10pt;font-family:Arial,sans-serif;color:rgb(155,155,155)"><span>mobile: +91-8095684687</span></td></tr><tr><td style="padding:0px;font-size:10pt;font-family:Arial,sans-serif;color:rgb(155,155,155)"><span>email: </span><span style="color:rgb(23,147,210)"><a href="mailto:ujaval@spatialthoughts.com" target="_blank">ujaval@spatialthoughts.com</a></span></td></tr><tr><td style="padding:6px 0px 0px"><span style="display:inline-block;height:22px"><span><a href="https://www.linkedin.com/in/spatialthoughts/" style="background-color:transparent;color:rgb(51,122,183)" target="_blank"><img alt="LinkedIn icon" border="0" width="23" height="23" src="https://codetwocdn.azureedge.net/images/mail-signatures/generator/elegant-logo/ln.png" style="border:0px;vertical-align:middle;height:20px;width:20px"></a> </span><span><a href="https://twitter.com/spatialthoughts" style="background-color:transparent;color:rgb(51,122,183)" target="_blank"><img alt="Twitter icon" border="0" width="23" height="23" src="https://codetwocdn.azureedge.net/images/mail-signatures/generator/elegant-logo/tt.png" style="border:0px;vertical-align:middle;height:20px;width:20px"></a> </span></span></td></tr></tbody></table></td></tr><tr><td colspan="2" style="padding:8px 0px 0px;border-top:1px solid rgb(23,147,210);width:480px;font-family:Arial,sans-serif;color:rgb(155,155,155);text-align:justify"></td></tr></tbody></table><br></div></div></div></div></div></div></div></div></div></div></div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Jun 1, 2021 at 1:59 PM Alister Hood <<a href="mailto:alister.hood@gmail.com">alister.hood@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div>Hi everyone,<div><br></div><div>I found that if a line touches itself, if I use the vector overlay "clip" algorithm on that layer, the feature gets broken up into 3 pieces (I can tell by running it through the "multipart to singleparts" algorithm).</div><div><br></div><div>See the screenshot below of some example inputs, and
I've attempted to attach the layers. If I run the line layer through "multipart to singleparts" it produces a layer with only one feature. But if I use the polygon to clip the line layer, and then run it through "multipart to singleparts" it gets split
at the point where it touches itself, into three pieces.</div></div><div><br></div><div>I haven't been able to find a tool for validating or repairing geometries that thinks there is a problem with the original geometry, so I think this is a bug with the clip algorithm. Should I file a ticket?</div><div><br></div><div>Or should the original geometry be considered invalid, so I can't expect the algorithm to preserve it as a single feature? If that's the case do we need a better tool for validating or repairing geometries, which can identify geometries with this problem?).</div><img src="cid:ii_koe284z70" alt="image.png" width="420" height="358" style="outline: 0px;"><br></div><div dir="ltr"><br></div><div>Regards,</div><div>Alister</div></div>
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