I've solved my needs about the creation of a new layer, but I feel that the mechanism a bit counter-intuitive. A new layer can be created *only* through an intemediary vector
>> v.category input=rivers output=rivers_tmp layer=2 >> g.remove vect=rivers >> g.rename vect=rivers_tmp,rivers Directly creating a new connection on a new layer produces the new layer, but the categories are not attached: >> v.db.connect map=rivers table=rivers_clone layer=2 and the vector *seems* to have a new layer, but it cannot be used. I see the same results if I create a new layer through the wxGUI (vector attributes window -> new layer). A new layer is shown, but it cannot be used (eg cannot be displayed). I will open a ticket on this. giovanni 2011/11/20 G. Allegri <gioha...@gmail.com> > I'm having some doubts on the layer mechanism. > Two questions in this point. > > 1) Creating a new layer (ie a new connection between a vector and a DB > table) > I've imported a vector (rivers) through v.in.ogr, then I've cloned the > original table: > >> db.copy from_table=rivers to_table=rivers_clone > I've created a new connection: > >> v.db.connect map=rivers table=rivers_clone layer=2 > > At this point I supposed that the last command had created all the needed > structures and fields for the new layer (2), but if I print the categories: > >> v.category input=rivers layer=2 option=print > no categories are displyed (while they are listed if I choose layer 1) > > Question: I thought that a new connection used the same vector categories, > but it seems I was wrong. How to make the layer 2 use the same vactor > categories from layer 1? > > 2) I haven't understood the purpose of v.category chlayer option. > The manual says that the commands change layer numbers. If I understand it > correctly, it changes the numbering of the vector-db connections, right? > Whatever it means I wonder why a new vector is created. If I have a vector > with layers 1,2 I thought that chlayer let me swap the numbers, but if it > creates a new vector it doesn't change the layer numbers, it creates a new > layer with the new layer number... I'm confused > > Help :) > thx, > giovanni >
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