Thank you for your reply! I find your answers and queries extremely helpful.
I tried to import GADM all at once, and it crashed badly. Plus, in version 6.4, if it had run, it would have still taken a long time. Australia alone took 30 hours of computer time. I used the -o because even though it was in the same projection as my location, there was some complaining by GRASS, so I just chose to override the complaining. I would not have chosen to use any snap or threshold settings, but GRASS 6.4 refused to import the shapes otherwise. It may be that I was only able to get the ESRI Geodatabase version, and then I used Arc View to convert it to a shapefile. Perhaps that step caused all of the snap issues. Tim *************************************************************** Timothy S. Thomas, Research Fellow, IFPRI [email protected] +1-202-862-4605 skype: timothy.s.thomas Rm 5035 -----Original Message----- From: Markus Metz [mailto:[email protected]] Sent: Monday, August 09, 2010 3:10 PM To: Thomas, Timothy (IFPRI) Cc: [email protected]; Nelson, Gerald (IFPRI) Subject: Re: [GRASS-user] GADM & Polygon files in general Thomas, Timothy (IFPRI) wrote: > > It leads naturally into a few questions. > > > 2) Since I have over 1,000 hours of computer time in converting using > GRASS 6.4 on Linux with 8GB RAM, what in the world happened in GRASS 7 > that it can now do it in only 4 hours??? > First, I imported the whole thing at once, not each country separately. Second, some under-the-hood modifications in GRASS 7 of the cleaning procedures result in reduced memory consumption and faster import. > 3) Would someone be able to tell me whether the commands I have been > using are the most efficient and correct, or whether that was the cause > of the slow speed in the first place? > > For importing a shapefile, I used a command like: > > v.in.ogr dsn=gadm1 layer=usa_gadm1 out=usa_gadm1 -o Why the -o flag? GADM shapefiles come with a *.prj file, i.e. projection information is available and should not be ignored. > > And if they do not have great boundaries, a command like > > v.in.ogr dsn=gadm1 layer=usa_gadm1 out=usa_gadm1 snap=0.00002 -o > Looks ok, but gadm is AFAICT clean, snapping boundaries is not necessary. > To combine 2 countries, I would use something like > > v.patch -e in=usa_gadm1,can_gadm1 out=namer_gadm1 > Watch out for category values when patching. I would prefer to import the whole thing at once, or the county you are interested in. > And to repair the boundaries, something like > > v.clean namer_gadm1 out=namer_cln_gadm1 tool=snap,break,rmdupl > thresh=0.00002 Looks ok, but for gadm this should not be necessary. Markus M _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
