Hi Huidae, FWIK, the reason why updating raster maps is currently not supported in GRASS at the module level is the storage format. Usually raster maps are stored using zip compressed rows. Rows are written in serial, hence if you modify a single row, the size of this row may be different after compression and does not fit exactly in the position of the old row in the existing file. From my knowledge there is currently no way to append rows or mark rows as invalid in existing raster maps. However, there is the possibility to store raster maps using uncompressed rows, but i don't recall any raster library function to update such maps.
Best regards Soeren 2014-06-26 15:05 GMT+02:00 Huidae Cho <[email protected]>: > Whenever I change a couple of cells in an existing raster map, I have to > create a new raster map and patch the old and new maps, which can take long > because r.patch has to read and write the entire map. > > There are Rast_open_old/new, but no Rast_open_update and AFAIK there are no > raster modules that directly update existing raster maps. I don't know why. > I thought it would be great if there was Rast_open_update so we can update > existing raster maps without creating a temp map and patching it. > > > _______________________________________________ > grass-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-dev _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
