[GRASSLIST:4236] Re: Generating new linked attribute table after v.overlay

[Radim Blazek]

I worry that I haven't got what you exactly want. 
You have 3 polygon layers?:
- trail (one or more cats?)
- vegetation 
- states
Do you need a table with area_size, vegetation_type, state
in the trail (or outside trail)?

Radim

On Monday 23 August 2004 20:36, Craig Aumann wrote:
> I'm afraid that's only part of the solution I need. Imagine you have a
> trail (represented as a polygon in a separate map layer) running through
> different kinds of vegetation types. Each polygon in the vegetation map
> links off to an attribute table.  I want to overlap the trail with the
> vege map so that I know which parts of the trail are in which types of
> vegetation and upload this information to the original attribute table
> so that each distinct trail-vegetation type polygon links to its own
> record in the database. After this, I will then do another v.overlay
> (with option NOT) so that the trail will then be represented with
> distinct vegetative types (i.e., TRAIL-ASPEN, or TRAIL-PINE) in the
> map.
>
> See my code below for precisely what I mean.
>
> ## Set the CAT values according to the vegetative classes.
> v.reclass input=vegelayer output=vegereclass type=area \
>     field=2 col=cover
>
> ## Do the overlay.
> v.overlay ainput=seismicinterclean binput=vegereclass bfield=1 \
>     output=seismicvegetemp operator=and
>
> ## Create new CAT values in field 2.  These will be used so that each
> ## vegetative polygon in the overlay links to a single row in the
> ## table.  I add 1000000 to ensure these values are distinct from the
> ## previous values used to link this table to the original "vegelayer"
> ## map.
>
> v.category input=vegereclass output=seismicvegetemp2 \
>     option=add field=2
> v.category input=seismicvegetemp2 output=seismicvegetemp3 \
>     option=sum field=2 cat=1000000
>
>
> ## Connect the map to this table.
> v.db.connect  -o map=seismicvegetemp3 table=play_att \
>     field=2 key=link_key \
>     driver=pg database="dbname=alpac_netdown,user=caumann"
>
> ## Create new rows in the table for each new polygon
> ## resulting from the overlay.
> v.to.db  map=seismicvegetemp3 field=2 option=cat type=centroid
>
>
> NOW, HOW DO I UPLOAD THE CAT VALUES IN FIELD 1 (WHICH CONTAIN THE
> VEGE STATE CLASS THIS POLYGON INTERESECTED) TO THE TABLE SO
> THAT I CAN EXECUTE QUERIES AND ASSIGN NEW STATE CLASSES USING THOSE
> VALUES?????
>
>
> Cheers!
> Craig
>
> On Mon, 2004-08-23 at 03:57, Radim Blazek wrote:
> > Reclass first input vectors by state ID (v.reclass col=STATE),
> > then run v.overlay and the table linked to field 1 contains
> > what you want.
> >
> > Radim
> >
> > On Saturday 21 August 2004 00:54, Craig Aumann wrote:
> > > I'm working in 5.7.
> > >
> > > Suppose we have two polygons which have attributes linked to an
> > > associated PostGRESQL database.
> > >
> > > i.e.
> > >
> > > ----------------
> > >
> > > |   1   |  2    |
> > >
> > > -----------------
> > >
> > > linking off to a table:
> > >
> > > LINK_KEY   STATE
> > > 1           57
> > > 2           59
> > >
> > >
> > > I now overlay  another polygon:
> > > ----------------
> > >
> > > |   10  |  11   |
> > >
> > > *******************
> > >
> > > |   12  |  13   |
> > >
> > > ******************
> > >
> > > |   14  |  15   |
> > >
> > > -----------------
> > >
> > > and what I want to do is end up with an associated table linked to the
> > > result of the overlay that looks like this:
> > >
> > > LINK_KEY  STATE NEW_STATE
> > > 10          57       57
> > > 11          59       59
> > > 12          57      157
> > > 13          59      159
> > > 14          57       57
> > > 15          59       59
> > >
> > > I need a few kicks in the right direction (alright, I need to have my
> > > hand held in a major way!) to figure out how to proceed following
> > > v.overlay to  ensure that each new polygon resulting from the overlay
> > > has one (and only one!) unique link_key into the new attribute table
> > > AND also how to do the associated query processing based on the STATE
> > > (and other columns) of the original polygons (stored in their original
> > > linked table above) which the overlaid polygon intersects.
> > >
> > >
> > > Thanks!
> > > Craig