Raster to Vector Conversion

[Malcolm Williamson]

?indiana?edu??at?Jan?12??95?09?02?07?pm at bnr.ca>
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>
> I've just downloaded the Linux Binaries for GRASS hoping to find a
> utility which can convert a raster image to a dxf file.  I have 20
> source files which are 5100x3300 bitmaps in targa format.  The
> bitmaps are scans of floor plans which I need to convert to dxf for
> import into AutoCAD.  Is this something GRASS can do?  If so, are
> there pitfalls?  Is the output quality high?
>
> I would endeavor to find this out for myself, but I've got to produce
> drawings for bids in one and a half weeks.  I appreciate any advice
> you can lend on this topic, or pointers to other Raster to Vector
> resources.
>
> Thanks,
> Scott
> email: srouten at antimony.service.indiana.edu
>
>
>
I'm not familiar with targa format, but I'm fairly confident that GRASS cannot
import it directly. Therefor, you need to convert it to a format that can be
read into GRASS, such as Sun raster format. I'd suggest using the pbmplus
utilities for the raster conversion (tgatopnm | pnmtorast -s ) - these are
available in various locations on the 'Net. After getting this data into GRASS
in raster format, you would use either r.line or r.poly to generate vector data
,
depending on if the data represents line-type features or polygons (areal
features). Polygon features will result in jagged edges where the vectors follo
w
the edge of rectangular raster cells - I believe there is a "-s" flag with
r.poly that will smooth this out a little. Given the size of your raster files,
conversion may take a while. Nope, I don't know of any better *free* way!

--
Malcolm D. Williamson - GIS Specialist           E-mail: malcolm at cast.uark.edu
Center for Advanced Spatial Technologies      Telephone: (501) 575-6159
Ozark Rm. 12                                        Fax: (501) 575-3846
University of Arkansas
Fayetteville, AR 72701