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--></style></div><div>Hi Michel,<br></div><div><br data-mce-bogus="1"></div><div>Never use epsg 3857 for measurement beacuse it is not a "projection"... </div><div>this "pseudo projection mercator" 3857, called often "Popular Visualisation<!--StartFragment--><!--EndFragment-->" is pseudo.... Because only use for <!--StartFragment-->visualization applications.<!--EndFragment--> <br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>example in France : 3200 km for a road for example, instead of 2100 km in a real projection (as local zone UTM or a Lambert projection)<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>So, you can use qgis, esri, postgis etc... the measurment with 3857 will be always bad, due to a "false" calcul from origine 0,0 (equateur cross greenwich) and "false" ellipoide etc....<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>best regards,<br data-mce-bogus="1"></div><div>Julien<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>have a look on :<br data-mce-bogus="1"></div><div>http://spatialreference.org/ref/sr-org/6864/<br data-mce-bogus="1"></div><div><br></div><div data-marker="__SIG_PRE__"><hr>
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</tbody></table><div><br></div></div><div><br></div><hr id="zwchr" data-marker="__DIVIDER__"><div data-marker="__HEADERS__"><b>De: </b>"Michel Stuyts" <michel.stuyts@edegem.be><br><b>À: </b>"Springfield Harrison" <stellargps@gmail.com><br><b>Cc: </b>"qgis-user" <qgis-user@lists.osgeo.org><br><b>Envoyé: </b>Vendredi 18 Mai 2018 08:44:01<br><b>Objet: </b>Re: [Qgis-user] results Measure Tool vs. length()<br></div><div><br></div><div data-marker="__QUOTED_TEXT__">
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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" lang="EN-US">$length gives the same result as length($geometry)</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US" lang="EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US" lang="EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Michel<br>
<br>
</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif" lang="NL">Van:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif" lang="NL"> Springfield Harrison [mailto:stellargps@gmail.com]
<br>
<b>Verzonden:</b> vrijdag 18 mei 2018 2:52<br>
<b>Aan:</b> Michel Stuyts <michel.stuyts@edegem.be><br>
<b>CC:</b> qgis-user <qgis-user@lists.osgeo.org><br>
<b>Onderwerp:</b> Re: [Qgis-user] results Measure Tool vs. length()</span></p>
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<p>Interesting and alarming observation.</p>
<p>And how do those results compare with output from the $length variable?</p>
<p>Cheers . . . . . Springfield<br>
Samsung Tab 4</p>
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<p class="MsoNormal">On May 17, 2018 5:26 AM, "Michel Stuyts" <<a href="mailto:michel.stuyts@edegem.be" target="_blank">michel.stuyts@edegem.be</a>> wrote:</p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">In the length() function QGIS uses the CRS unit of the layer to calculate the result. When I use for example a layer in a local CRS like EPSG:31370 or EPSG:5439
and a layer in EPSG:3857 (that all use meters as unit) the results are very different (+40% difference). Changing the project CRS makes no difference. When I check the length using the Measure Tool the results are very similar to the local CRS.</span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> </span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">How can I measure the length of a line and use it as a label independent from the layer CRS and get results similar to the results of the Measure Tool?</span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> </span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">Michel</span></p>
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