On 23/05/07 16:20, Moritz Lennert wrote:
On 23/05/07 15:50, Salvator*eL*arosa wrote:
hajhouse wrote:
På 2007-05-22, skrev Salvator*eL*arosa:
hi,
i need a little help!
How can to export a point shapefile from a polygon layer in Grass
(Convert
Polygon2Point)?
So, i can have in table (point file) all informations of the layer
polygon
table!Sorry my english!
Thanks!
In GRASS terminology polygons can be lines, boundaries, or areas (when
conbined with a centroid [= center point]). So assuming you have areas
and you want to export just the centroids, I believe something like:v.type type=centroid,point in=mymap out=mymap_converted
v.out.ogr in=mymap_converted dsn=myshapefile.shp
would meet your needs.Thank u for reply!
Unfortunately it doesn't work, yet. It export always shp polygon!
I need of a point shapefile!You need to use the type= option of v.out.ogr:
v.type type=centroid,point in=mymap out=mymap_converted
v.out.ogr in=mymap_converted dsn=myshapefile.shp type=pointThen you get a point file with attributes.
This has made me try and wonder: v.out.ogr's type option contains 'centroid' as one of the possibilities, so in my understanding something like
v.out.ogr in=fields type=centroid dsn=~/ olayer=fields
should work, exporting only the centroids. But I get the following messages:
GRASS 6.3.cvs (spearfish60):~ > v.out.ogr in=fields dsn=~/ olayer=fields type=centroid
WARNING: 208 Boundary(ies) found, but not requested to be exported. Verify
'type' parameter.
Exporting 271 points/lines...
ERROR 1: Attempt to write non-point (LINESTRING) geometry to point shapefile.
[repeated 63 times]
63 features written
I don't know where the error message comes from, I imagine it must be the OGR libraries.
v.type type=centroid,point in=fields out=fp
v.out.ogr in=fp dsn=~/ olayer=fields type=point
works as expected.
Is this a bug in v.out.ogr, or am I misunderstanding something ?
Moritz