How do I increase polyline length

Mr_Kirkwood

I have 250 polylines. I have a value i calculated (all different) that needs to be added to the length of the. The values are in the attribute table. How can I increase the length of the lines using the values in the table as the distance to add to the lines? 

JoshuaBixby

Not sure if there is a tool that directly addresses this.  I know this question has been asked in one form or another on GeoNet and StackExchange, so I encourage a bit more searching.

If you up for some basic scripting, the following code snippet should work or get you most of the way there:

<SPAN class="keyword token">import</SPAN> math

fc <SPAN class="operator token">=</SPAN> <SPAN class="comment token"># Path to feature class containing lines to be extended</SPAN>
dist_fld <SPAN class="operator token">=</SPAN> <SPAN class="comment token"># Name of field containing distance to extend line</SPAN>

<SPAN class="keyword token">with</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>da<SPAN class="punctuation token">.</SPAN>UpdateCursor<SPAN class="punctuation token">(</SPAN>fc<SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="string token">"SHAPE@"</SPAN><SPAN class="punctuation token">,</SPAN> dist_fld<SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">as</SPAN> cur<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">for</SPAN> line<SPAN class="punctuation token">,</SPAN> dist <SPAN class="keyword token">in</SPAN> cur<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; SR <SPAN class="operator token">=</SPAN> line<SPAN class="punctuation token">.</SPAN>spatialReference
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; parts <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>Array<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">for</SPAN> part <SPAN class="keyword token">in</SPAN> line<SPAN class="punctuation token">.</SPAN>getPart<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; pn1<SPAN class="punctuation token">,</SPAN> pn <SPAN class="operator token">=</SPAN> part<SPAN class="punctuation token">[</SPAN><SPAN class="operator token">-</SPAN><SPAN class="number token">2</SPAN><SPAN class="punctuation token">:</SPAN><SPAN class="punctuation token">]</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; angle <SPAN class="operator token">=</SPAN> math<SPAN class="punctuation token">.</SPAN>atan2<SPAN class="punctuation token">(</SPAN>pn<SPAN class="punctuation token">.</SPAN>Y <SPAN class="operator token">-</SPAN> pn1<SPAN class="punctuation token">.</SPAN>Y<SPAN class="punctuation token">,</SPAN> pn<SPAN class="punctuation token">.</SPAN>X <SPAN class="operator token">-</SPAN> pn1<SPAN class="punctuation token">.</SPAN>X<SPAN class="punctuation token">)</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; p <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>Point<SPAN class="punctuation token">(</SPAN>pn<SPAN class="punctuation token">.</SPAN>X <SPAN class="operator token">+</SPAN> dist <SPAN class="operator token">*</SPAN> math<SPAN class="punctuation token">.</SPAN>cos<SPAN class="punctuation token">(</SPAN>angle<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">,</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; pn<SPAN class="punctuation token">.</SPAN>Y <SPAN class="operator token">+</SPAN> dist <SPAN class="operator token">*</SPAN> math<SPAN class="punctuation token">.</SPAN>sin<SPAN class="punctuation token">(</SPAN>angle<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; part<SPAN class="punctuation token">.</SPAN>append<SPAN class="punctuation token">(</SPAN>p<SPAN class="punctuation token">)</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; parts<SPAN class="punctuation token">.</SPAN>append<SPAN class="punctuation token">(</SPAN>part<SPAN class="punctuation token">)</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; line <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>Polyline<SPAN class="punctuation token">(</SPAN>parts<SPAN class="punctuation token">,</SPAN> SR<SPAN class="punctuation token">)</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; cur<SPAN class="punctuation token">.</SPAN>updateRow<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN>line<SPAN class="punctuation token">,</SPAN>dist<SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>
‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

The above code simply linearly extrapolates the line that connects the last two vertices of the line.  If you want different line fitting/extending, you can implement a different formula.

NOTE:  The ArcPy Array slicing on line 11 requires ArcGIS 10.4.1.  If you are using an earlier version the line can be modified.

pn1<SPAN class="punctuation token">,</SPAN> pn <SPAN class="operator token">=</SPAN> arr<SPAN class="punctuation token">[</SPAN>len<SPAN class="punctuation token">(</SPAN>arr<SPAN class="punctuation token">)</SPAN><SPAN class="operator token">-</SPAN><SPAN class="number token">2</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> arr<SPAN class="punctuation token">[</SPAN>len<SPAN class="punctuation token">(</SPAN>arr<SPAN class="punctuation token">)</SPAN><SPAN class="operator token">-</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN></SPAN>