Wow guys. 131 seconds is a lot faster than 10 days. Remi, if you can work out a fast intersection method that uses points and lines as a preprocessor to dealing with the polygons, I think it would be a great addition to PostGIS. ST_Intersection in PostGIS is often quite a bit slower than the implementation in Geomedia, Mapinfo, and (I hear) ArcGIS, so any functionality that results in speed improvements would be great.
Mark, I can't wait to figure out why your system was fast! I was following your (preliminary) tutorial and gridding the data was progressing very slowly. I have a provincial boundary file but there seems to be much ambiguity in GIS representations of the provincial boundary, so I won't send you the one I have. I can try to assemble one from other sources. -- John Abraham [email protected] 403-232-1060 On Feb 25, 2015, at 6:28 AM, Mark Wynter <[email protected]> wrote: > Hi John > > I’ve just crunched your whole dataset. The process takes 131 seconds for the > vector tiling (using a 16 CPU machine). Plus another 170 seconds for data > prep at the start including making the poly's valid. > For a 2 CPU machine, it will take circa 15 minutes, or double that using a > single CPU. > > Only one small issue outstanding - and that relates to clipping the regular > grid prior to tiling. For clipping I used the union of the > abmiw2wlcv_48tiles as supplied with the data - the problem is the > abmiw2wlcv_48tiles are rough and ready, which produces voids. The voids using > my method unfortunately get the same feature class as lc_class = 32. You’ll > see this clearly on second screenshot. > The way around this is to clip the regular grid using a high-res shapefile of > the Alberta state boundary prior to the tile crunching the > lancover_polygons_2010 table. This is easily done - I just didn’t have the > state boundary data. > > I need to get some sleep. John, Remi, I will share with you the code > tomorrow. For others, I’ll be posting a tutorial that steps through the > methods touched upon in this thread.. > > John, the only difference between my tutorial and its application to your > land cover data was a few tweaks to the data prep stage. Otherwise the same > code pattern (no modification at all needed to the worker_function). It was > great to test the code with your data. > > Speak tomorrow. > Mark > > > > > <Screen Shot 2015-02-25 at 11.29.15 pm.png> > > > <Screen Shot 2015-02-25 at 11.39.04 pm.png> > > > <Screen Shot 2015-02-25 at 11.41.41 pm.png> > _______________________________________________ postgis-users mailing list [email protected] http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
