Plotting a polygon from relative coordinates

Question

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 1Central 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!!

Ed

Hornbydd · Answer

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.

JimCousins · Answer

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