topic Re: Incidence angle between line segments in Geoprocessing Questions

Incidence angle between line segments

JimFritz — Thu, 15 Nov 2018 20:46:41 GMT

Does anyone have a script or know of a tool that can calculate incidence angle between line segments? I've done some searching and there does not appear to be a tool that can do this. Also, there are other solutions but none that compare line segments that are coincident to each other. In this case, it is a collection of transmission lines that are separated by poles (nodes) and need to know when an incidence angle is greater than 30 degrees between one arc (line segment) and the next coincident arc (line segment).

Thank-you,

Jim Fritz

Re: Incidence angle between line segments

DuncanHornby — Fri, 16 Nov 2018 11:48:04 GMT

Jim,

You are more likely to get a reply if you show an image of your data or your problem you want to solve, as what you think is crystal clear to you can often be interpreted in many other ways by the rest of us. That said are you asking to compute the angle as I have drawn below? Red points are your poles and black lines are straight lines between them?

Re: Incidence angle between line segments

JimFritz — Fri, 16 Nov 2018 15:17:06 GMT

Duncan,

Yes, an image would have helped.

Looking for the interior angle. The angle value would ideally be assigned to the pole attribute table.

Re: Incidence angle between line segments

DuncanHornby — Fri, 16 Nov 2018 15:36:27 GMT

Have you explored the ESRI code sharing website? Did not take long to find this tool? This could help

https://www.arcgis.com/home/item.html?id=d02d22b2130342a4998b2bf8b2b1156d

Re: Incidence angle between line segments

JimFritz — Fri, 16 Nov 2018 15:45:40 GMT

Thanks, I did not. I will take a look.

Re: Incidence angle between line segments

Scott_Harris — Fri, 16 Nov 2018 18:10:56 GMT

Also see: https://community.esri.com/thread/20473

Re: Incidence angle between line segments

JimFritz — Tue, 27 Nov 2018 15:01:06 GMT

Duncan,

Using the code in field calculator from the link above (see attached jpg) yields a processing error, also attached in a jpg. Maybe something simple?

Thanks,

Jim

Re: Incidence angle between line segments

DanPatterson_Retired — Tue, 27 Nov 2018 15:19:55 GMT

!Shape! not !SHAPE!

Re: Incidence angle between line segments

RichardFairhurst — Tue, 27 Nov 2018 15:24:06 GMT

You did not check the Python option at the top of the Field Calculator. The code will definitely not work if the VB Script option is checked.

Re: Incidence angle between line segments

JimFritz — Tue, 27 Nov 2018 15:24:28 GMT

Thanks, but the same error message appears.

Re: Incidence angle between line segments

DanPatterson_Retired — Tue, 27 Nov 2018 15:25:25 GMT

fix both errors and try again

Re: Incidence angle between line segments

JimFritz — Tue, 27 Nov 2018 15:28:01 GMT

Thanks, Dan and Richard!

Re: Incidence angle between line segments

DuncanHornby — Tue, 27 Nov 2018 15:31:52 GMT

Python is case sensitive. I would have written it as:

shape.firstPoint.X

Note P and X are upper case.

Re: Incidence angle between line segments

JimFritz — Tue, 27 Nov 2018 15:51:01 GMT

OK, that's the first part of my original question: how to assign the incidence angle between adjacent vectors to the point in-between both?

Re: Incidence angle between line segments

JimFritz — Tue, 27 Nov 2018 17:18:00 GMT

Re-thinking what is needed is not necessarily the point receiving the incidence angle but instead assigning the polyline layer an attribute with the value of the difference between adjacent vector angles. So, in the example above, without doing the math it appears that the incidence angle would be nearly 90 degrees. (The angle measurements appear to be from the X-axis.) Once that value is computed a query showing which vectors have an incidence angle greater than or equal to 30 degrees could be made.

Any thoughts about the math needed to compute this value would be appreciated. High school geometry re-visited!

Re: Incidence angle between line segments

AnaDeniston — Mon, 27 Sep 2021 21:22:40 GMT

Hi Ducan,
I know this problem is pretty old, but I develop a tool that extracts inflection points. I will attach a toolbox here in case anyone comes across this issue again.