topic Re: Plotting a polygon from relative coordinates in Geoprocessing Questions

Plotting a polygon from relative coordinates

EdPearson — Fri, 12 Oct 2018 15:47:18 GMT

Good afternoon all.

I am trying to plot a series of polygons that are regularly updated.

Each polygon is made up of a series of 8 points that are referenced with a range and bearing from a central point that has a location (given in WGS84 DDM2 format). Is there already a tool that exists that will plot a polygon based on points that don’t have individual XY cordiates, only relative to a single point?

Example data below:

Header 1

Central point	40 30.10N
	005 20.35W
Bearing	Range
001	30
045	35
090	38
135	42.5
180	38
225	30
270	27.65
315	25

Any advice or pointers greatly appreciated!!

Re: Plotting a polygon from relative coordinates

JimCousins — Mon, 15 Oct 2018 14:49:51 GMT

Ed, Have a look at coordinate geometry (COGO). I have created parcels from similar datasets by hand, using the bearing / distance drawing tool from the edit toolbar, but I do not have an automated solution.

Regards,

Jim

Re: Plotting a polygon from relative coordinates

DuncanHornby — Thu, 25 Oct 2018 14:04:07 GMT

As you are asking for a tool I assume you have many polygons to construct and the manual approached suggested is probably not viable for you?

I'm not aware of any out of the box tool that will do this, you will need to script it. You would need to use trigonometry to create the vertices of the polygon you want to construct. This Q&A on GIS SE has the salient code. I have developed a tool that generates fixed length lines that uses bearing and distance. This code was written in python using arcpy so you can examine the code to work out how to do it.

Looking at your example, I assume the range are in metres? You would need to project the central coordinate to a coordinate system that uses feet or metres as units.

If coding in python is beyond your skill level then you either have to hang around until someone kindly offers up the code or employ a GIS developer.