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Topic: a shapewrite question
Replies: 2   Last Post: Apr 25, 2013 1:11 PM

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Bruce Bowler

Posts: 236
Registered: 12/7/04
Re: a shapewrite question
Posted: Apr 25, 2013 12:39 PM
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On Thu, 25 Apr 2013 16:28:08 +0000, Kelly Kearney wrote:

> Bruce Bowler <bbowler@bigelow.org> wrote in message
> <att0stFnudtU1@mid.individual.net>...

>> I've got shapewrite mostly doing what I want, but the application that
>> I'm using to eventually read the shapefile is complaining about the
>> lack of a .prj file. Is there a 'secret' to getting matlab to create
>> one? I've not looked in detail to see if I understand enough to make
>> my own.
>>
>> Any shapefile experts out there who can point me in the right
>> direction?
>>
>>

> Matlab's shapefile tools ignore the projection component of a shapefile,
> so you'd have to write this yourself.
>
> Is the data that you're writing into your shapefile actually projected,
> i.e. x/y coordinates based on a projection rather than straight lat/lon?
> If the latter, I wouldn't think you'd need a projection file; the file
> basically tells the software how to translate the data in the file to
> and from lat/lon. But I'm not sure if ArcGIS or other software gets
> picky about this. If you do have projected coordinates, the data you'll
> need is found in the map projection structure (e.g. structure produced
> by defaultm) that corresponds to your data.
>
> This website gives a good overview of the .prj format:
> http://docs.geotools.org/stable/javadocs/org/opengis/referencing/doc-

files/WKT.html.
>
> I've written some functions for reading projected shapefiles into
> Matlab, but have never tried to reverse the process. However, if you're
> interested in looking at those functions, contact me via email and I can
> send them to you (they're not quite up to my public distribution
> standards, so I'd rather not post them to the FEX quite yet).
>
> -Kelly


It's actual lat/lon values, so I didn't think I needed one either, but who
knows what the other software's doing (I've asked them for help too, but
of course CSSM is WAY faster :-)

Bruce



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