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    <p>Hi again,</p>
    <p>On that matter: If you can isolate only the arc-part of your
      geometry, you could that circular arc into the Postgis-function
      "ST_MinimumBoundingRadius()" to detect center-point and radius.
      See
      <a class="moz-txt-link-freetext" href="http://www.postgis.net/docs/manual-2.5/ST_MinimumBoundingRadius.html">http://www.postgis.net/docs/manual-2.5/ST_MinimumBoundingRadius.html</a>
      - maybe worth a try?</p>
    <p>Sample query:</p>
    <p>SELECT ST_AsText(center), radius<br>
         FROM ST_MinimumBoundingRadius('CIRCULARSTRING(220268
      150415,220227 150505,220227 150406)');</p>
    <p>RESULT:</p>
    <p>"POINT(220237.62195122 150455.5)"    "50.6268293270462"<br>
    </p>
    <p>Greetings,</p>
    <p>Andreas<br>
    </p>
    <div class="moz-cite-prefix">Am 29.04.19 um 18:21 schrieb Cory
      Albrecht:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAMW5rYKpFbfEqJmTmPDNxrmQK5khGMdc_gqrJ9-gQDh3qoJc_Q@mail.gmail.com">
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      <div dir="ltr">I tried saving a few layers that had arcs and
        circles (x,y, r coords), but QGIS converts each curve to a bunch
        of straight line segments instead of saving them as curves. :-(</div>
      <br>
      <div class="gmail_quote">
        <div dir="ltr" class="gmail_attr">On Mon, Apr 22, 2019 at 3:33
          AM McDonaldR <<a href="mailto:McDonaldR@angus.gov.uk"
            moz-do-not-send="true">McDonaldR@angus.gov.uk</a>> wrote:<br>
        </div>
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          0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
          <div lang="EN-GB">
            <div class="gmail-m_4032411246367673761WordSection1">
              <p class="MsoNormal"><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)">As your
                  data is in PostGIS and assuming that they are arcs
                  (curved lines part of a circle) you could use some
                  geometry and spatial SQL functions to calculate the
                  radius of any curve knowing the coordinates of the end
                  points of the curve.</span></p>
              <p class="MsoNormal"><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)"> </span></p>
              <p class="MsoNormal"><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)">To quote
                  the pseudo code on the linked page:</span></p>
              <p class="MsoNormal"><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)"> </span></p>
              <p class="MsoNormal"><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)">“</span><span
style="font-family:Arial,sans-serif;color:black;background:rgb(251,251,251)">To
                  calculate the radius of an arc, take the height -- "H"
                  -- of the arc and divide it by two. Call the result
                  "C." Now take the width -- "W" -- of the arc and
                  square it by multiplying it by itself. Call the result
                  "D." Next multiply height, "H," by eight and call this
                  result "E." Divide "D" by "E" and call the result "F."
                  The radius of the arc is C plus F.”</span><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)"></span></p>
              <p class="MsoNormal"><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)"> </span></p>
              <p class="MsoNormal"><a
                  href="https://sciencing.com/calculate-radius-curve-7804090.html"
                  target="_blank" moz-do-not-send="true">https://sciencing.com/calculate-radius-curve-7804090.html</a><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)"></span></p>
              <p class="MsoNormal"><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)"> </span></p>
              <p class="MsoNormal"><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)">Could
                  probably be wrapped in a function and run against any
                  curve.</span></p>
              <p class="MsoNormal"><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)"> </span></p>
              <p class="MsoNormal"><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)">Ross</span></p>
              <p class="MsoNormal"><span
                  style="font-size:11pt;font-family:"Century
                  Gothic",sans-serif;color:rgb(31,73,125)"> </span></p>
              <p class="MsoNormal"><b><span
                    style="font-size:11pt;font-family:Calibri,sans-serif"
                    lang="EN-US">From:</span></b><span
                  style="font-size:11pt;font-family:Calibri,sans-serif"
                  lang="EN-US"> Qgis-user [mailto:<a
                    href="mailto:qgis-user-bounces@lists.osgeo.org"
                    target="_blank" moz-do-not-send="true">qgis-user-bounces@lists.osgeo.org</a>]
                  <b>On Behalf Of </b>Cory Albrecht<br>
                  <b>Sent:</b> 19 April 2019 17:08<br>
                  <b>To:</b> <a href="mailto:qgis-user@lists.osgeo.org"
                    target="_blank" moz-do-not-send="true">qgis-user@lists.osgeo.org</a><br>
                  <b>Subject:</b> Re: [Qgis-user] finding the radius of
                  a curve</span></p>
              <p class="MsoNormal"> </p>
              <div>
                <p class="MsoNormal">I'll give it a try. Thanks!</p>
              </div>
              <p class="MsoNormal"> </p>
              <div>
                <div>
                  <p class="MsoNormal">On Sun, Apr 14, 2019 at 7:52 AM
                    Mike Flannigan <<a href="mailto:mikeflan@att.net"
                      target="_blank" moz-do-not-send="true">mikeflan@att.net</a>>
                    wrote:</p>
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style="border-top:none;border-right:none;border-bottom:none;border-left:1pt
                  solid rgb(204,204,204);padding:0cm 0cm 0cm
                  6pt;margin-left:4.8pt;margin-right:0cm">
                  <p class="MsoNormal" style="margin-bottom:12pt"><br>
                    Draw a circle and measure the diameter/radius.<br>
                    <br>
                    Maybe use this plugin to create a circle:<br>
                    <a
                      href="https://plugins.qgis.org/plugins/CADDigitize/"
                      target="_blank" moz-do-not-send="true">https://plugins.qgis.org/plugins/CADDigitize/</a><br>
                    <br>
                    <br>
                    Mike<br>
                    <br>
                    <br>
                    On 4/13/2019 2:00 PM, <a
                      href="mailto:qgis-user-request@lists.osgeo.org"
                      target="_blank" moz-do-not-send="true">
                      qgis-user-request@lists.osgeo.org</a> wrote:<br>
                    > Hello all,<br>
                    ><br>
                    > I'm looking for a way to find the radius of a
                    curve (for roads, railyways)<br>
                    > in QGIS. If it were a paper map I could do it
                    with a drafting compass<br>
                    > (calipers to some) and a ruler, but this is a
                    PostGIS layer.<br>
                    ><br>
                    > Any plugin recommendations or links to a set of
                    steps to accomplish this?<br>
                    > Thanks in advance!</p>
                </blockquote>
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