[R-sig-Geo] creating a shp file from a tiff file

[Barry Rowlingson]

On Sat, May 14, 2011 at 5:44 AM, Hodgess, Erin <HodgessE at uhd.edu> wrote:
> Dear R Sig Geo People;
>
> I have a question which I suspect might be very simple, but here it goes:  I have a tiff file would like to create a shp file.
>
> So far, I have used the readTiff function to create a pixmap.  But I'm not sure where to go from here.
>
> My goal is to create a shp file to be used in ArcGIS, please.
>
> Thanks for any help.

 Right, you want to convert from a raster grid (tiff) to a vector
format. There's a number of ways this could go down, depending on
exactly what you have and what you are trying to do...

 Firstly, is the tiff showing points, lines, or polygons?

 Does the tiff show the outlines, as if it was a scan of a line map,
or is it solid shading of areas? Are all the values in solid areas
exactly the same, or is it noisy?

  How many bands is it?

 I'm sure there are ways to do many of these things in R (and in
GRASS, definitely) but you need to be a bit clearer about the
transformation you are trying to do!

Barry