Le 24 janvier 2017 18:42:22 GMT+01:00, Raphael Knevels <[email protected]> a écrit : >Dear GRASS-community, > > > >I have to perform a multi-scale, object-oriented analysis on an image >with >about 93'535'000 pixels^^ > > > >I'm doing the process on a server, so I need for one simple >segmentation >process approximately 700-800 minutes depending on the threshold.
This does seem rather long. Is your computational region set to the extent and resolution of your raster ? Also try setting the memory parameter of I.segment to a higher value (depending on your server's resources). Which thresholds have you tried ? >The >same >process in SAGA takes around 60 minutes with the use of seed points (as >grid >pixels). Which segmentation algorithm do you use in SAGA ? >But in SAGA there is no possibility for hierarchical >segmentation. >Therefore, I would like to use the seed points of SAGA as Input for >GRASS >7.2.0 to speed up i.segment. > > > >However, I am not capable to transform the seeds of SAGA to a >meaningful >i.segment input. How has to look an optimal input seeds grid for GRASS? > > > >- I've already found out is that it must be an integer grid with >positive >seed numbers. The float-grid output of SAGA seed contains single pixels >surrounded by no-data values. When I transform the SAGA seed to an >integer >grid and into GRASS (by (r)gdal), I have to give no data values a >positive >number. Negative values in the seed-grid-input lead to an error in >i.segment. Seeds in i.segment have to be polygons not points. These polygons are represented by identical positive integer values (= IDs) in adjacent pixels, and they have to cover the entire region. When used as seeds for a segmentation, these polygons are the further merged. I don't really understand what your seed points represent, but unless they have a semantic meaning related to the objects you are trying to identify, I'm not sure they are really relevant. You could try using the brand new i.superpixels.slic add-on to create superpixels which you can then use as seeds. Moritz _______________________________________________ grass-user mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/grass-user
