<div dir="ltr"><div>I am working with a projected vector layer (EPSG:31287) that, after dissolving polygons, has just two areas with no more than 20 vertices each. The total area should be exactly one million square meters.</div><div>When I use the Add Geometry Attributes function, the sum of the calculated areas is less than a square millimeter off. When I use instead the $area variable in the field calculator, the sum is some 670 square meters off.</div><div>What is the difference in the underlying algorithm of the two operations involved?</div><div>Cheers,</div><div>       Jochen</div><div><br></div><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><span><div dir="ltr" style="margin-left:0pt" align="left"><table style="border:none;border-collapse:collapse;table-layout:fixed;width:496.79999999999995pt"><colgroup><col><col><col></colgroup><tbody><tr style="height:21pt"><td colspan="2" style="vertical-align:top;padding:5pt 5pt 5pt 5pt;overflow:hidden"><p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-family:Arial;vertical-align:baseline;white-space:pre-wrap">Dr. Jochen Albrecht, GISP (he/him/his)</span></p><p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-family:Arial;background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Professor for Computational and Theoretical Geography</span></p><p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><a href="http://www.geo.hunter.cuny.edu/" target="_blank"><span style="font-family:Arial;background-color:transparent;vertical-align:baseline">Department of Geography and Environmental Science</span></a></p><p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-family:Arial;background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Hunter College CUNY</span></p><p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-family:Arial;background-color:transparent;vertical-align:baseline;white-space:pre-wrap">695 Park Avenue</span></p><p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-family:Arial;background-color:transparent;vertical-align:baseline;white-space:pre-wrap">New York, NY 10065</span></p><p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-family:Arial;background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Immediate Past-President, </span><a href="https://www.gisci.org/" target="_blank"><span style="font-family:Arial;color:rgb(17,85,204);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">GIS Certification Institute</span></a></p><img width="200" height="80" src="https://ci3.googleusercontent.com/mail-sig/AIorK4yQa-R1jr4PDfKlAVSkcKgWO3idZiszzQ4etZD-AdOX8KMIvWz46Zq_m6pYHsin8-Lnnz5eRfo"><br></td><td style="vertical-align:top;padding:5pt 5pt 5pt 5pt;overflow:hidden"><p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"><span style="border:none;display:inline-block;overflow:hidden;width:141px;height:139px"></span></span></p></td></tr></tbody></table><b style="color:rgb(34,34,34);font-family:"Google Sans",Roboto,RobotoDraft,Helvetica,Arial,sans-serif"><br></b><br></div></span></div></div></div></div>