Estimate the vegetation area included in the ellipse(about footprint)
1.To estimate the vegetation area included in each ellipse, which spatial analysis fountion could I use?
2. I would like to know how to estimate the vegetation area included in each ellipse, which spatial analysis fountion could I use to "cut" the vegetation polygons with each ellipse?
3.I try to use the ST_intersection but failed,I can not get the intersection of the geom and the footprint;
--create table cont_veg as select a.Time, a.Wdir,a.z0,a.KM_p01a,a.KM_p01b,a.KM_p01c, ST_area(st_intersection(a.footprint, b.ST_Union)) as veg_cont from footprint_ART_def a,veg_uni b where st_intersects(a.footprint, b.ST_Union);
and could you tell me the exactly meaning of the 'veg_cont'?
4.For the rotation angle (radians) of the ellipse in the x,y projection (in ST_makeellipse) how can I get it ?
Re: Estimate the vegetation area included in the ellipse(about footprint)
Maybe you don't remember the exercices done in courses ... but we already answered this kind of questions.
You have two kind of geometries :
1- the vegetation area (polygon)
2- the footprint area (polygon) --> ellipse
So if you you want to determine, in each ellipse the area of vegetation, you have to cut (with st_intersection) the vegetation which is in an ellipse (better to choose ST_Intersect).
When the vegetation is cutted, you have to sum the area (ST_Area) of each pieces that are in each ellipses.