Dr. Manuel Seeger wrote: > we have obtained huge airborne laserscanner data, and want to try out > the modules in GRASS. .. > Another question. How many points can be handled with grass and these > modules (or grass vector files in general)?
For vector point data loaded with v.in.ascii & the default settings you can probably get up to ~1 million points before running out of memory. (happens in the "building lines" step of building topology, watch memory grow with `top`, M) see the NOTES section, http://grass.ibiblio.org/grass63/manuals/html63_user/v.in.ascii.html The first thing you do can do to save memory is -t to skip creating a DB table. If data is just x,y,z you don't need one, just use -z and make a 3D vector map. (no DB table is the default if no extra columns besides xyz?) This will get you up to ~1 million(?) points before running out of memory. Next you could try the new (6.3 only) v.in.ascii -r flag to only import points which are in the current region (area of interest). [g.region] The final v.in.ascii flag to try is -b, which skips building topology altogether. This means that the new vector can't be used for much, but the max point limit becomes 25+ million (as high as Helena's has tested I think). Then you start to get into LFS 2gb file size problems, ..? While there isn't much you can do with a vector map without topology, one important thing you can do is run v.surf.rst to make a surface. It is hoped that v.surf.idw(2) and v.univar can be updated to work with them as well. The "other way" is to use r.in.xyz to create a raster directly from the points. This is very fast and the only limit is from the LFS issues, but I'd guess you could load 4gb of data without a problem. It is hoped to one day update r.in.xyz to optionally read data from stdin, in which case you can avoid and file system issues*. Then AFAIK there would be no limit, as no file to open. LFS support is much better for rasters than it is for vectors currently. [*] would need to disable scan mode if input=stdin http://grass.ibiblio.org/grass63/manuals/html63_user/r.in.xyz.html http://hamish.bowman.googlepages.com/grassfiles#xyz Hamish _______________________________________________ grassuser mailing list [email protected] http://grass.itc.it/mailman/listinfo/grassuser
