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 [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
