Hi all,
I have a watershed map in Arcview shapefile format, which consists of 9 watersheds(polygons). I imported it into grass using
v.in.ogr -o dsn=/home/vishal/CRU/shpfiles layer=watershed9 type=boundary output=watershed9
Two of the polygons have a common boundary. When i run the above command, i get at the end the following message, which basically says that i have overlapping polygons. (But the attribute table lists all 9, and d.what.vect also seems to differentiate between the polygons with common boundary).
WARNING: 1 areas represent more (overlapping) features, because polygons
overlap in input layer(s). Such areas are linked to more than 1
row in attribute table. The number of features for those areas is
stored as category in layer 2.
9 input polygons
total area: 2.518677e+09 (61 areas)
overlapping area: 5.874115e+08 (1 areas)
area without category: 0.000000e+00 (0 areas)
I need to convert this into a raster map:
v.to.rast input=watershed9 output=watershed9 use=cat
and then use r.average with v.what.rast on a bunch of rasters to add columns of data from the rasters to my watershed vector map.
BUT, when i convert the above vector into raster, the 2 polygons are getting merged into one category in the raster output.
I’ve tried using v.clean on the imported vector, but there’s no difference. If i go ahead anyway and use v.what.rast (after duly converting the centroid type to point type), Null data fills the columns pertaining to the overlapping polygons.
How can i solve this?
thanks,
vishal