[GRASSLIST:4708] v.out.ogr

GRASS GRASS user
1

Hello all,

I am using Grass57 to convert some raster maps to vector. I used the r.to.vect command to generate some polygons from one of the categories in a raster layer. I then wanted to export these polys to a shapefile to clean them up in another software package. For some reason v.out.ogr runs very slowly when exporting areas and after a while stops processing altogether. No such problems when exporting area boundaries, but I would really like to create a polygon shapefile. Has anyone seen this problem before? Any suggestions for an alternative way to get the data out of Grass and into a shapefile?

Thanks in advance,

Eliot Cline

2

I am using Grass57 to convert some raster maps to vector. I used the r.to.vect command to generate some polygons from one of the categories in a raster layer. I then wanted to export these polys to a shapefile to clean them up in another software package. For some reason v.out.ogr runs very slowly when exporting areas and after a while stops processing altogether. No such problems when exporting area boundaries, but I would really like to create a polygon shapefile. Has anyone seen this problem before? Any suggestions for an alternative way to get the data out of Grass and into a shapefile?

You might try v.out.shape?

v.out.shape map=vfile type=point,line,area mapset=PERMANENT cats=string log=this

For large vector files v.prune is helpful. Ex.

v.prune input=vfile output=vfile.prune thresh=1000
cp vfile.prune vfile1

then for only polygons

v.out.shape map=vfile1 type=area mapset=PERMANENT cats=string log=this

lp

3

Eliot Cline wrote:

Hello all,

I am using Grass57 to convert some raster maps to vector. I used the r.to.vect command to generate some polygons from one of the categories in a raster layer. I then wanted to export these polys to a shapefile to clean them up in another software package. For some reason v.out.ogr runs very slowly when exporting areas and after a while stops processing altogether. No such problems when exporting area boundaries, but I would really like to create a polygon shapefile. Has anyone seen this problem before? Any suggestions for an alternative way to get the data out of Grass and into a shapefile?

Thanks in advance,

Eliot Cline

Probably because areas were created as WKT and then converted to WKB,
I have changed that to create directly WKB and it reduced time
form 16s to 1s for my test data. Try CVS.

Radim