[postgis-users] Intersection - three tables

[Sufficool, Stanley]

Assuming you do not have features between n & f that overlap at
discontiguous points:

Sum(area2d(ST_Intersection(STGeometryN(ST_Intersection(n.the_geom,
f.the_geom),1), c.the_geom)))*0.000247105381

> -----Original Message-----
> From: Marcus C. England [mailto:marcuscengland at gmail.com] 
> Sent: Thursday, June 05, 2008 7:15 PM
> To: Sufficool, Stanley
> Cc: PostGIS Users Discussion
> Subject: Re: [postgis-users] Intersection - three tables
> 
> 
> Hi Stanley,
> 
> I tried that several times and it never worked. Nonetheless, I copied 
> your text and placed it into my query (replacing the original sum 
> function) and it still did not work. I get this:
> 
> NOTICE:  IllegalArgumentException: This method does not support 
> GeometryCollection arguments
> 
> 
> ERROR:  GEOS Intersection() threw an error!
> 
> ********** Error **********
> 
> ERROR: GEOS Intersection() threw an error!
> SQL state: XX000
> 
> -Marcus
> 
> Sufficool, Stanley wrote:
> > The sum of the intersecting area of all 3 polygons.
> >
> > Sum(area2d(ST_Intersection(ST_Intersection(n.the_geom, f.the_geom), 
> > c.the_geom)))*0.000247105381
> >
> >
> >   
> >> Hello all,
> >>
> >> Well, I'm learning fast but I have come across a problem that
> >> perplexes 
> >> me. I have three polygon tables. "new_vegetation" represents 
> >> vegetation 
> >> on a site. "grading_phases" represents the grading area for a 
> >> project, 
> >> and this is entirely within the limits of 
> "new_vegetation". The third 
> >> layer is "basin_grading", which represents five proposed 
> >> basins (as well 
> >> as polygons for 100' and 200' buffers around those 
> basins), some of 
> >> which are within "grading_phases" and some of which are outside of 
> >> "grading_phases". Some are even split between being and out of 
> >> grading_phases.
> >>
> >> What I am trying to get is the acreage of vegetation communities
> >> (new_vegetation) within the each polygon type of 
> >> basin_grading, but only 
> >> those portions that are within grading_phases. The query 
> below is my 
> >> attempt at this, but it returns the acreage of 
> new_vegetation within 
> >> each entire basin, not just the portion that is also within 
> >> grading_phases. I thought the ST_Intersects part would 
> take care of 
> >> that, but apparently not.
> >>
> >>
> >> SELECT
> >>    f.use,
> >>    n.cat_2008,
> >>    Sum(area2d(ST_Intersection(n.the_geom, 
> >> f.the_geom)))*0.000247105381
> >>     
> >
> >   
> >> AS inside_project
> >>  FROM
> >>    basin_grading f,
> >>    grading_phases c,
> >>    new_vegetation n
> >>  WHERE
> >>    ST_Intersects(c.the_geom, f.the_geom)
> >>  GROUP BY f.use, n.cat_2008
> >>  ORDER BY f.use, n.cat_2008
> >>
> >> thanks in advance,
> >>
> >> Marcus
> >> _______________________________________________
> >> postgis-users mailing list postgis-users at postgis.refractions.net
> >> http://postgis.refractions.net/mailman/listinfo/postgis-users
> >>
> >>     
> >
> >   
> 
> 
> 
>