<div dir="ltr"><div>And note that the correct signature</div><div><br></div>geometry ST_CoverageClean(geometry winset geom, float8 gapMaximumWidth = 0, float8 snappingDistance = -1, text overlapMergeStrategy = 'MERGE_LONGEST_BORDER');<div><br><div>means that the best-practice pattern for using the function is to simply specify the maximum gap width, leaving the snapping tolerance and overlap merge strategy as defaulits:</div><div><br></div><div>CREATE TABLE  example1_c AS<br>  SELECT id,  ST_CoverageClean(geom, 1) OVER () AS GEOM<br>  FROM  example1;</div><div><br></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Tue, Oct 7, 2025 at 10:49 AM Paul Ramsey via postgis-users <<a href="mailto:postgis-users@lists.osgeo.org">postgis-users@lists.osgeo.org</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">If I told you there is an error in the documentation and that the actual signature is this, would that allay your concerns?<div><br></div><div><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(0,92,197);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">ST_CoverageClean</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">(</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">geom</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">geometry</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">,</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">gapMaximumWidth</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(215,58,73);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">float8</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(215,58,73);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">default</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(0,153,153);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">0</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">.</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(0,153,153);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">0</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">,</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">snappingDistance</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(215,58,73);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">float8</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(215,58,73);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">default</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(215,58,73);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">-</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(0,153,153);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">1</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">.</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(0,153,153);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">0</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">,</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">overlapMergeStrategy</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(68,85,136);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">text</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"></span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(215,58,73);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">default</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(187,187,187);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"> </span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(204,122,0);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"></span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(16,99,3);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">'</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(16,99,3);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">MERGE_LONGEST_BORDER</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(16,99,3);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">'</span><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">)</span><br></div><div><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial"><br></span></div><div><span style="white-space:pre-wrap;box-sizing:border-box;border-width:0px;border-style:solid;border-color:currentcolor;color:rgb(24,28,33);font-family:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace,"Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji","Twemoji Mozilla";font-size:12px;font-variant-ligatures:normal;background-color:rgb(255,251,221);text-decoration-style:initial;text-decoration-color:initial">P.</span></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Sep 23, 2025 at 5:25 AM Douglas Fan <<a href="mailto:douglas.mhfan@gmail.com" target="_blank">douglas.mhfan@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">Dear PostGIS Developers and Users,<br><br>First of all, thank you for the development of the new ST_CoverageClean function in PostGIS 3.6.0. It’s a fantastic addition that has already helped a lot in my work with polygonal coverages. I really appreciate the effort that went into making this tool available.<br>While testing the function, I’ve encountered some behaviors that I’d like to better understand, particularly regarding the snappingDistance and gapMaximumWidth parameters.<div><br>From the documentation, I understand that:<br>1. snappingDistance controls vertex snapping, with -1 applying an automatic distance, and 0.0 disabling snapping.<br>2. gapMaximumWidth closes gaps smaller than the specified tolerance.<br><br>However, during testing with various combinations (e.g., snappingDistance set to -1, 0.0, 1, 2 and gapMaximumWidth set to 0, 1, 2), I noticed:<br>1. Even when snappingDistance is explicitly set to 0.0, small sliver vertices still appear to be snapped or altered when gapMaximumWidth is greater than 0.<br>2. Slivers that are thinner than the gapMaximumWidth are removed, even when they are not actual gaps or overlaps. <br><br>This behavior seems counterintuitive, as I expected no snapping to occur with snappingDistance = 0.0. Could this be due to internal gap cleaning logic that also affects vertex positions? Or is there an implicit snapping step tied to gapMaximumWidth?<br><br>I’d be grateful for any insights into:<br><br>1. How do these two parameters interact?<br>2. Best practices or recommended workflows for cleaning polygonal coverages with minimal geometry distortion.<br>3. Any known edge cases or limitations when using ST_CoverageClean.<br>4. Whether gapMaximumWidth also triggers geometry simplification or sliver removal beyond gap closing.<br><br>Thanks in advance for your help and for the continued development of PostGIS.<br><br>Best regards,<br>Man Ho Fan</div></div>
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