[GRASS-user] Extracting line heights from 3d vectors

Nick Cahill ndcahill at wisc.edu
Sat Nov 29 12:25:01 EST 2008


Ah, right you are -- I added columns x,y,z to the table and then ran  
v.to.db option=start columns=x,y,z and it worked perfectly. Many thanks!

Nick Cahill


On Nov 28, 2008, at 7:14 PM, Hamish wrote:

> Nick wrote:
>> I have a series of contour vector maps imported from a CAD
>> program (Microstation). The CAD maps were in 3d, and the 3d
>> information was successfully imported into GRASS, so the
>> vectors have line heights as well as length, etc. Now I need
>> to export these into shapefiles. When I do this, all the
>> other useless CAD data like line color, style, weight, etc.
>> is exported as attributes in the .dbf file, but line height
>> is not -- it is not a field in the mySQL database but is
>> part of the geometry of the line, if I understand what's
>> going on here correctly. Is there a way to transfer line
>> height into the attribute table so I can access and export
>> it? Many thanks,
>
> v.db.addcol + v.to.db ?
>
> note that unless lines are perfectly horizontal (eg elevation  
> contours)
> you can not assign a single elevation value to a line's attributes (as
> each vertex will have its own value, and the attribute is associated  
> with
> the line as a whole), so I would expect in general for it to refuse  
> to try.
>
> as for 3D shapefile export, ummm... check the wiki, help pages, and ML
> archives. It rings a bell but I've no idea how.
>
>
> Hamish
>
>
>
>
>



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