topic Re: Calculate Z values of 3D Polyline for new vertices in Python Questions https://community.esri.com/t5/python-questions/calculate-z-values-of-3d-polyline-for-new-vertices/m-p/409401#M32291 <HTML><HEAD></HEAD><BODY><P>Well, once you have moved or inserted vertices, the only way is to re-interpolate the elevation from the dem using interpolate shape. To calculate an elevation from the vertex before and after would be a mistake surely? What if you have reshaped a small segment of line to better follow the stream bottom (which is what you appear to be doing).</P><P>So without the original dem, where are the elevations coming from?</P><P>The line segment geom object could be fed into Interpolate shape to create an in_memory fc, then update the original from that.</P></BODY></HTML> Thu, 11 Aug 2016 16:39:58 GMT NeilAyres 2016-08-11T16:39:58Z Calculate Z values of 3D Polyline for new vertices https://community.esri.com/t5/python-questions/calculate-z-values-of-3d-polyline-for-new-vertices/m-p/409399#M32289 <HTML><HEAD></HEAD><BODY><P>I've created a 3D polyline from a 3D point feature class and then reshaped the polyline feature class to follow the meandering of the river thawleg (centreline). I would like to calculate the Z values for the new vertices that are added to the 3D polyline based on the existing vertices that already have Z values and the distance along the polyline as a linear proportion of the elevation drop. Is there a way that I can achieve the following in&nbsp; python.</P><P></P><P><IMG __jive_id="215135" class="image-1 jive-image" src="https://community.esri.com/legacyfs/online/215135_pastedImage_1.png" style="max-width: 1200px; max-height: 900px;" /></P><P>Points (Red) were used to create the 3D polyline</P><P></P><P><IMG __jive_id="215137" class="image-2 jive-image" height="610" src="https://community.esri.com/legacyfs/online/215137_pastedImage_3.png" style="width: auto; height: auto;" width="532" /></P><P>New vertices added through reshaping 3D Polyline</P></BODY></HTML> Thu, 11 Aug 2016 15:10:41 GMT https://community.esri.com/t5/python-questions/calculate-z-values-of-3d-polyline-for-new-vertices/m-p/409399#M32289 PeterWilson 2016-08-11T15:10:41Z Re: Calculate Z values of 3D Polyline for new vertices https://community.esri.com/t5/python-questions/calculate-z-values-of-3d-polyline-for-new-vertices/m-p/409400#M32290 <HTML><HEAD></HEAD><BODY><P>Not to nitpick, but a <EM>thalweg</EM> is often not the same as a centerline. A <EM>thalweg</EM> is the lowest point in a waterbody and in a moving waterbody that meanders it will be found on the <STRONG><EM>outside of the curve</EM></STRONG> (not in the center).&nbsp; Depending upon what your goal is of this analysis, that can throw things a bit if centerline data is used instead of <EM>thalweg </EM>location data.</P><P></P><P><A href="https://en.wikipedia.org/wiki/Thalweg" title="https://en.wikipedia.org/wiki/Thalweg">Thalweg - Wikipedia, the free encyclopedia</A></P><P></P><P></P><P><IMG alt="thalweg_asymetrical.jpg" class="image-2 jive-image" src="https://community.esri.com/legacyfs/online/215166_thalweg_asymetrical.jpg" style="width: 620px; height: 229px;" /></P><P></P><P><IMG __jive_id="215165" alt="thalweg.jpg" class="image-1 jive-image" src="https://community.esri.com/legacyfs/online/215165_thalweg.jpg" style="width: 620px; height: 207px;" /></P><P><A href="http://aerialgeologist.blogspot.com/2015/04/thawing-thalweg.html" title="http://aerialgeologist.blogspot.com/2015/04/thawing-thalweg.html">images source:&nbsp; Aerial Geologist: Thawing Thalweg</A></P><P></P><P>EDIT - added images from the link to help folks better visualize the spatial location of a thalweg.</P><P></P><P></P><P>Chris Donohue, GISP</P></BODY></HTML> Thu, 11 Aug 2016 15:44:28 GMT https://community.esri.com/t5/python-questions/calculate-z-values-of-3d-polyline-for-new-vertices/m-p/409400#M32290 ChrisDonohue__GISP 2016-08-11T15:44:28Z Re: Calculate Z values of 3D Polyline for new vertices https://community.esri.com/t5/python-questions/calculate-z-values-of-3d-polyline-for-new-vertices/m-p/409401#M32291 <HTML><HEAD></HEAD><BODY><P>Well, once you have moved or inserted vertices, the only way is to re-interpolate the elevation from the dem using interpolate shape. To calculate an elevation from the vertex before and after would be a mistake surely? What if you have reshaped a small segment of line to better follow the stream bottom (which is what you appear to be doing).</P><P>So without the original dem, where are the elevations coming from?</P><P>The line segment geom object could be fed into Interpolate shape to create an in_memory fc, then update the original from that.</P></BODY></HTML> Thu, 11 Aug 2016 16:39:58 GMT https://community.esri.com/t5/python-questions/calculate-z-values-of-3d-polyline-for-new-vertices/m-p/409401#M32291 NeilAyres 2016-08-11T16:39:58Z Re: Calculate Z values of 3D Polyline for new vertices https://community.esri.com/t5/python-questions/calculate-z-values-of-3d-polyline-for-new-vertices/m-p/409402#M32292 <HTML><HEAD></HEAD><BODY><P>There is a Python Code sample in the help section for Interpolate Shape that may be use.&nbsp; Note that it requires access to the <EM>3D Analyst extension</EM>.</P><P><A href="http://pro.arcgis.com/en/pro-app/tool-reference/3d-analyst/interpolate-shape.htm" title="http://pro.arcgis.com/en/pro-app/tool-reference/3d-analyst/interpolate-shape.htm">Interpolate Shape—Help | ArcGIS for Desktop</A> </P><P></P><P></P><P>Chris Donohue, GISP</P></BODY></HTML> Thu, 11 Aug 2016 17:32:04 GMT https://community.esri.com/t5/python-questions/calculate-z-values-of-3d-polyline-for-new-vertices/m-p/409402#M32292 ChrisDonohue__GISP 2016-08-11T17:32:04Z