Regarding filename matching etc. I would just wrap everything in a scripting language of your choice (bash, python, ruby etc.) considering all the GMT programs, including grdmath, are command line tools.
-ra On 23 Nov 2015, at 16:27, Rasmus Aveskogh <ras...@defero.se> wrote: > > Though this is probably possible in PostGIS nowadays I would personally solve > such a use case with GMT (http://gmt.soest.hawaii.edu/), for example with > grdmath (http://gmt.soest.hawaii.edu/doc/5.2.1/grdmath.html) which lets you > perform rather complex computations on multiple grids (for examples rasters) > using reverse polish notation. > > -ra > > On 23 Nov 2015, at 13:20, Darrel Maddy <darrel.ma...@newcastle.ac.uk> wrote: > >> Dear all, >> >> As you know I am relatively new to postgis and SQL and therefore I have >> much to learn. However, I am facing a paper deadline and need to do some >> quick analysis of the data I have and I am struggling to figure out how best >> to pursue what I need to do. >> >> I have a significant number of rasters which have double precision values. >> Without going into detail about what the rasters represent, I need to >> extract and sum values from one set of rasters in say table A based upon >> values in another set of rasters in say table B where the pixel value in >> the raster from Table B exceeds a threshold. Both tables are the same size >> (rasters are tiled) but I also need to figure out how I make sure the >> correct rasters are compared. They have filenames like this >> rastervariable_10.tif, rastervariable_100.tif , presumably I need to use a >> logical expression to strip the numerical value (in this case this >> represents the year) and then order on that basis? >> >> I can do this in QGIS one at a time but that is a little clumsy and rather >> time consuming. >> >> If someone can just point me in the right direction I am sure I can figure >> out the rest for myself. >> >> Apologies once more for asking what is probably a rather trivial question >> and yet again demonstrating my ignorance. >> >> Many thanks >> >> Darrel >> _______________________________________________ >> postgis-users mailing list >> postgis-users@lists.osgeo.org >> http://lists.osgeo.org/mailman/listinfo/postgis-users >
_______________________________________________ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/postgis-users
