Thanks Micha, I've used v.to.db a bit, just not recently enough to remember that was my answer! Thanks for your tips/reminder, I should be OK in getting it to happen for me now :-) If you don't hear from me again on this, I've succeeded.
regards, shane. On Mon, 2012-01-30 at 10:01 +0200, Micha Silver wrote: > On 30/01/2012 09:52, Shane Litherland wrote: > > Hi all, > > > > I'm lost. I have looked around in GRASS for how to report the area (e.g. > > in hectares) for a vector map that, yes, has area (i.e. centroids and > > boundaries). > > > > I cannot find a way to do this. A bit of web searching, even gave some > > suggestions this basic facility may not be available in GRASS?? surely > > there's something tucked away to do it? > > > > I'm sure I've done something in the past to view vector area data, > > though it may have been area data that was already in a table. When I > > use the query tool in map display, it tells me 'nothing'. Seems that is > > because my vector is not connected to an attribute table. For the > > purpose of my exercise I did not need cats for the boundaries/centroids > > so I didn't bother with a table connection either. Maybe this is where > > I've gone wrong? > > > > I did try vector to raster to try and report on how many raster > > cells/area... no luck there either. > > > > I also tried the 'measure' tool in the map display, but it only gives > > distance. > > > > > > I could go and learn more about PostGIS for sending the vector data to a > > postgres geometry table and figure it out that way... I was hoping to > > find a way to do it in GRASS in a matter of minutes, not via a database > > and a couple of days/weeks of learning how... > > > > What tool/command should I be using? > > v.to.db is what you need. From the man page: > > > Upload polygon areas to corresponding centroid record in the attribute > table: > > v.to.db map=soils type=centroid option=area col=area_size unit=h > > You'll need to start by adding a database connection and a column for > area. Again in the man page there's a sample you can follow- just use > option=area instead of option=sides: > Upload category numbers of left and right area, to an attribute table > of boundaries common for the areas: > # add categories for boundaries of the input vector map, in layer 2: > v.category soils out=mysoils layer=2 type=boundary option=add > # add a table with columns named "left" and "right" to layer 2 of the > input > # vector map: > v.db.addtable mysoils layer=2 col="left integer,right integer" > # upload categories of left and right areas: > v.to.db mysoils option=sides col=left,right layer=2 > # display the result: > v.db.select mysoils layer=2 > > regards, > > Shane. > > > > _______________________________________________ > > grass-user mailing list > > grass-user@lists.osgeo.org > > http://lists.osgeo.org/mailman/listinfo/grass-user > > > > This mail was received via Mail-SeCure System. > > > > > > _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user