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Centre line of polygon

AndrewMcClune

I am trying to create a network from a set of polygons of roads, paths railway and water-ways. Does anybody know how to find the centre line of a polygon so that it will, for example, represent the centre line of a road.

Thanks

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KeaganAllan

I am trying to create a network from a set of polygons of roads, paths railway and water-ways. Does anybody know how to find the centre line of a polygon so that it will, for example, represent the centre line of a road.

Thanks

Hi Andrew,

I am not sure if you are familiar with ET Geowizards?
This set of tools is extremely useful for performing these types of tasks. It can be downloaded from www.ian-ko.com.

Looking at my version there is a tool that would allow you to generate a centerline from your polygon features. Copying straight from the help file it states:

Creates centerlines from polygon features.

Inputs:

A polygon feature class.
Centerline type:

Inside - the centerlines will be created inside the polygons - suitable for deriving centerlines from rivers and streets represented by polygons

Outside - the centerlines will be created in the gaps between polygons - suitable for deriving street centerlines from cadastral data.

Outputs:
New polyline feature class

I hope that helps, if not I am sure we can figure out a way.

Cheers,
K

AndrewMcClune

Brilliant that is very helpful

However is this tool in the free ET GeoWizards package. Having a look around the website it says that 'ET GeoWizard is not a free program' and unfortunately I am not able to purchase the full package

KeaganAllan

I think if your input file has less than 300 or 100 features then it is ok (what you can do is look at dissolving your input layer into a single feature and then split your output shapefile at a later stage).
The program is free to use, just to unlock the full features you need to purchase it.

Even if you are unable to purchase it, I highly recommend you download it, it has so many other useful tools that can speed up how you do things.

AndrewMcClune

Ok great. Thanks for the help Keagan

KeaganAllan

No problem.

good luck

AndrewMcClune

Having a few problems trying to run the polygon create centerline function. I can get as far as inputting the maximum and minimum width and from there I cannot go any further. It says that it is an unlicensed function. Do I therefore need to request the key or register the product, and if I do will there be any cost?

Thanks

KeaganAllan

How many features are there in your input file?
You could try a dissolve first to get them into a single feature and then try and run it.

Unfortunately I have not had much experince using that function in ET.
If that does not work, then a new way would potentially have to be used...I will give it some thought...

AndrewMcClune

I don't think it is effected by the number of input features. I have dissolved the polygons together to get an overall data set of 291, from an original 1974 but it still says it is an 'Unlicensed function'. I think the problem is that it is not registered so I may therefore need to register the product, hopefully at no extra cost. I will look into this.

Thanks anyway,

Andrew

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