[GRASS-user] How update vector layers?

Vincent Bain bain at toraval.fr
Fri Mar 6 04:29:30 EST 2009

Hi Thybério,

it is actually v.patch that you need to run for this purpose (AFAIU your
problem). v.patch allows to merge several maps with attribute
preservation (-e flag), but it only works for layer 1 features. I
suggest you to check if each linked table has the same columns

Instead of creating a new "merge" map, you can choose the "append file
to existing file" option (-a flag), then be carefull with the advice
given in the man page : "When using the -a flag, the user has to make
sure that the features in the different maps added to the output map do
not have overlapping category numbers, unless identical category numbers
reflect identical attributes, otherwise the attributes of the added maps
are lost".

After you perform v.patch don't forget to clean your vector (e.g.
removing duplicate features with v.clean)

Good luck,

Le jeudi 05 mars 2009 à 21:38 -0300, Thybério Luna Freire a écrit :
> I have a location with sugarcane areas. They are in a vector layer and
> each area have a line in a table in a pg database. There are new areas
> being planted in the farm and i have them in a shape file. I imported
> the new vectors and i want put them into the layer "sugarcane" to
> update it. My question is: how can i do it without interfering in the
> table structure and without to need create a new table? I tried
> v.overlay, but it adds new columns to the new table and a don't want i
> new table. Then, i tried v.patch, but this module is not apropriated
> to do this. It looks like very simple to do, but simply don't know
> how.
> Help me!!
> Thybério Luna - Brazil
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