[GRASSLIST:4241] Re: Generating new linked attribute table after v.overlay

Tue Aug 24 12:05:27 EDT 2004

No, its two polygon layers: trails and vegetation. I see I have confused
you by using state class and vegetation interchangeably.  

The trail polygon layer comes from buffering line features.  The
vegetation layer does not represent trails - it treats the landscape as
vegetation type without any human disturbances. What I want is to end up
with a single new vegetation layer which treats the trail as distinct
vegetation classes which are assigned by me: i.e., TRAIL-PINE,
TRAIL-ASPEN which result from the trail passing through PINE stands or
ASPEN stands.  Thus, the final vegetation layer will look like:

--------------------------------------
|   PINE | Trail-Pine |       PINE |
--------------------------------------

where before there just a single "PINE" polygon.  Why do I want this? 
Because this layer forms the input to a vegetation succession model. It
allows me to say that the successional dynamics of TRAIL-PINE vegetative
polygons are different from the successional dynamics of PINE polygons. 

In the code below, I got as far as adding rows into the attribute table
associated with the new TRAIL-VEGETATION layer.   The problem is, that
the vegetation class the trail intersected is in Field 1 (i.e., ASPEN,
PINE), and I have linked the attribute table to Field 2 which now
contains distinct LINK_KEYs.  How can I copy or get the cat values in
field 1 to the right rows in the attached attribute table via field 2?  

Once these values are upload, I can then easily assign new vegetative
state codes (Pine -> Trail-Pine.  Aspen -> Trail-Aspen) using SQL
queries.  

The following steps (which I know how to do) is to create the new
vegetative layer - which is done by first removing the trail polygons
from the original vegetative layer (NOT overlay) followed by merging in
the TRAIL-VEGETATION polygons using an OR overlay.  Given that I have
created distinct LINK_KEYs I should be able to link this final
vegetative layer to the modified attribute table and I'm off to the
races.  

I hope this clear things up. Perhaps there is an entirely different way
to do this.   

Cheers!
Craig

On Tue, 2004-08-24 at 02:48, Radim Blazek wrote:
> 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
> 