<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 70.85pt 70.85pt 70.85pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="NO-BOK" link="#0563C1" vlink="#954F72">
<div class="WordSection1">
<p class="MsoNormal">Dear all,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US">At the moment I am struggling quite a bit with GRASS topology errors for two of my maps which result from v.dissolve.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Input maps are imported with v.in.ogr without topological errors. However, the output maps from v.dissolve result into<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">406458 areas, but only<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">182176 centroids<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">in map A and <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">1058018 areas, but only<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">995283 centroids<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">in map B<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">After patching and cleaning both layers v.to.db gives no correct result for sides. Often areas have –sides like this:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">cat|left|right<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">1||-1|<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Then I ran v.build -e on both in order to investigate.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">For both, the number of errors reported by v.build is exactly the difference between the number of areas and the number of centroids in each map.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Any hints or suggestions for alternative approaches to dissolving areas with common attributes?
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I am interested in the individual areas (= one category and one entry in the attribute table per area) anyway and will try v.extract directly, if that sounds reasonable?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Cheers<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Stefan<o:p></o:p></span></p>
</div>
</body>
</html>