Hi, Thanks for the suggestions. I'm going to try a few experiments with our code, and probably get back to this later.
Regards, Michael A. ----- Original Message ----- > > ----- Original Message ----- > > > For sure doing overlay gis operations like st_intersection is not > > > possible when the srid of the two geometries is different. In this > > > case you would have to reproject (ST_Transform) the geometry so it > > > fit > > > the srid of right grid. But if your application is able to decide > > > which grid it must query then it should also be able to decide > > > which > > > tale it must query and hence putting all your grids in different > > > table > > > should not be a problem. > > > > For the general case (particularly in the coast example, where the > > queries are > > basically just Lon/Lat), we would not know which grid contains the > > answer. > > Consequently we would have to do two queries (one to determine the > > grid to > > query and one to query the specific grid), where today we make do > > with one. I > > suspect that this would cost us a fair bit of performance. > > You could have a table of the outlines of each dataset and use CASE to > determine to which srid reproject your point. All that in one query. > > > > You can easily get the x,y upperleft corner of a pixel with the > > > Raster2WorldcoordX(0,0) and Raster2WorldcoordY(1,0) functions. Is > > > that > > > what you need? > > > > Not quite - I was thinking more of World2RasterCoord, but using a > > geometry to > > extract multiple raster points. Essentially, ST_INTERSECT, but > > returning raster > > coordinates rather than world coordinates and value. > > You can extract every point of a complex geometry using a mixture of > ST_PointN(),ST_NPoints(),ST_NumGeometries() and ST_GeometryN(). Have a > look in the PostGIS doc. > > Pierre > _______________________________________________ > 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
