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Re: Edge detection and convert edges into polygons [message #61917 is a reply to message #61916]

Fri, 01 August 2008 08:06

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

M. Suklitsch writes:

> I need some hint on how to convert edges into vertices. What I want to
> do in the end is check whether a station (of which I have lon/lat
> values) lies within such a vertex.
>
> To be more precise: I have a netCDF file with three fields. longitude,
> latitude and mask, where mask has integer values and defines
> subregions. In this mask "image" I want to detect the edges, what I
> already got working using the tips on http://www.dfanning.com/ip_tips/sharpen.html.
>
> These edges I want to convert into vertices which I then put in an
> IDLanROI object. Using this object I could then very easily check if a
> station given by its longitude and latitude lies within a region or
> not.

I think I would just work with the integer mask and find
the boundaries around the sub-regions:

http://www.dfanning.com/ip_tips/boundary.html

You can use the boundary directly to create an IDLanROI
object, or (probably a good idea) you can reduce the
number of vertices in the boundary with MESH_DECIMATE
first.

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Re: Edge detection and convert edges into polygons By: M. Suklitsch on Mon, 04 August 2008 00:50
		Re: Edge detection and convert edges into polygons By: pgrigis on Fri, 01 August 2008 08:11
		Re: Edge detection and convert edges into polygons By: David Fanning on Fri, 01 August 2008 08:06

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