Hi Pierre, Thanks for the link to the add-on and the sql statements. Karl
Den onsdag den 27. november 2013 14.21.46 UTC-3 skrev Pierre Racine: > > Hi Karl, > > I do this with the ST_ExtractToRaster() function from the PostGIS Add-ons: > > https://github.com/pedrogit/postgisaddons/releases/tag/1.21 > > I just added a SUM_OF_LENGTHS method to ST_ExtractToRaster(). > > Look at the ST_ExtractToRaster() function in the postgis_addons.sql file > for an example. In your case it should look like this: > > SELECT ST_ExtractToRaster(ST_AddBand(ST_MakeEmptyRaster(rast), '32BF'), > 'public', 'geomtable', 'geom', null, 'SUM_OF_LENGTHS') rast > FROM refrastertable; > > You should have a reference raster already existing in a table and your > lines should be indexed. > > Pierre > > > -----Original Message----- > > From: [email protected] <javascript:> > > [mailto:postgis-users-<javascript:> > > [email protected] <javascript:>] On Behalf Of Karl Zinglersen > > Sent: Wednesday, November 27, 2013 11:30 AM > > To: [email protected] <javascript:> > > Cc: PostGIS Users Discussion > > Subject: Re: [postgis-users] Simple Line Density > > > > Hi, > > I am dealing with the same types of data and issues as Jeff. > > My procedure for data clean up is: > > 1) CSV files into PostGIS as points > > 1.1) ST_TRANSFORM to projected spatial reference (here EPSG:32621 / > > UTM zone 21 N WGS84) > > 2) ST_MAKELINE to "sub"-lines via PARTITION BY > > 3) Create a gridded polygon layer in same srid > > 4) Run equivalent to select cell_id, line_id from cells, lines where > > intersects(lines.geom, cells.geom > > - but my postgis runs out of memory after a while. And I am sorry to say > > Spatial Analyst doesn't. > > Is there more memory cheap way to do it in PostGIS (e.g. via the raster > > functions - although I haven't found i yet). > > > > Karl > > > > Den onsdag den 26. december 2012 09.58.43 UTC-3 skrev Jeff Adams - > > NOAA Affiliate: > > > > Hi Brent, > > > > Thanks for the response. I don't think your original response > made > > it into my inbox via the list, but now I see it on the website thread. > That > > seems like it might be a viable alternative, I just worry about those > vessel > > tracks that would be clearly outside of a particular grid cell, but > whose > > buffer would bleed over. How did you handle this type of situation? > > > > Jeff > > > > > > On Mon, Dec 24, 2012 at 7:22 PM, <[email protected] > > <javascript:> > wrote: > > > > > > Jeff, > > > > Did you see my reply using vessel tracklines as vectors & a grid in > Postgis to > > do exactly what you describe? > > > > Given we were looking at benthic impact, we buffered the tracklines to > > create polygons representing the swept area of the deployed fishing > gear. > > These were clipped by the cells, & we could generate statistics suca as > the > > cumulative swept area of all tracks with each cell, number of times each > cell > > was crossed, & given the tracklines have a timestamp associated with > them, > > we could also look at the temporal pattern of tracks crossing cells, for > > things like seasonal impacts & variation between seasons. > > > > Cheers, > > > > Brent Wood > > > > _______________________________________________ > postgis-users mailing list > [email protected] <javascript:> > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >
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