[GRASS-user] v.to.rast to get nice smooth vector-based pngs ?

[Felix Schalck]

Hi,

Thanks to the support of this mailing list, I managed to paste and
import a huge amount of NASA swbd tiles into a GRASS vector-layer,
aimed at completing the hydrography of my relief-map. My initial plan
was to export the GRASS vector layer to svg and rework it with
inkscape, before final rasterization, and merging with the topographic
layer. Unfortunately, the exported svg map is far to big to be edited
with inkscape, at least on my hardware (AMD64, 3Gb ram and about 350Gb
hdd).

My first attempt was to simplify the vector layer first, using
v.simplify, but it produces weired results by mixing water and land
areas. A possible explanation for this would be the "-c" flag I used
during the import operation, which skipped the usual cleaning process,
mainly because that cleaning already produced weired results.

Second choice would be a GRASS-lead direct rasterization; I mean,
given the tools offered by this GIS, why using inkscape. After all,
all I want is a nice anti-aliased raster, based on the vector layer,
with blue lines (rivers, coastlines), and light-blue areas (water
bodies). I learned about v.to.rast again, thanks to this mailing list,
but unfortunately, I don't really know how to use it.  All my testings
result in a white raster, showing only green waterbodies. I tried to
investigate this, and found that v.to.rast seems to rely heavily on
the attribute table of my vector map - and it looks like it (attribute
table) contains ONLY areas with centroids, eg waterbodies: there are
only two colums, first one cat number (1-52492), and second one
entitled "FACC_CODE", with either value 'BA040' or 'BH080'