read on overviews in these 2 links http://www.gdal.org/gdaladdo.html
http://www.gdal.org/frmt_gtiff.html On Thu, Jun 12, 2014 at 10:46 AM, Julian Schall <[email protected]> wrote: > Dear Jukka, > > > > thank you for your answer. > > I still don’t know how to build pyramids just for defined scale ranges (in > my case: smaller then 1:25.000). > > I’ve forgotten to tell you an –maybe important- detail: I’m working with a > virtual raster catalogue which i built out of 875 .jpgs (4000x4000). > > When building pyramids, i’ve always used the option “external (Erdas > Image.aux)”. > > Can you shortly explain the difference between the 3 options (external > .ovr, internal, external .aux)? > > I couldn’t find an advice in the handbook or via google. > > The QGIS instructions say that after building pyramids QGIS automaticly > takes the best resolution when loading raster layers. So how can I > influence what resolution QGIS chooses? > > > Thanks again for further help! > > Kind regards, > > > Julian Schall > > > > > > Date: Thu, 12 Jun 2014 09:34:18 +0000 (UTC) > > From: Jukka Rahkonen <[email protected]> > > To: [email protected] > > Subject: Re: [Qgis-user] QGIS: Reduction of resolution via pyramids > > only for defined scale range > > Message-ID: <[email protected]> > > Content-Type: text/plain; charset=utf-8 > > > > Julian Schall <j.schall@...> writes: > > > > > > > > > > > Hello members of the mailing list, > > > ? > > > I would appreciate help on the following problem: > > > I would like to improve the performance of a raster layer. Of course I > can > > build pyramids for that purpose. But in the scale ranges from 1:1 to > > 1:25.000 I need maximum resolution and detail. In this scale range, the > > performance is sufficient even without pyramids. > > > Ideal would be that the pyramids respectively the reduction of the > > resolution with improvement of performance is only applied to scales > smaller > > than 1:25,000. Is this possible in QGIS? > > > ? > > > Thanks for helpful answers! > > > ? > > > Kind regards > > > ? > > > Julian Schall > > > > There are check boxes for overview levels in the Build overviews panel. > > Level 2 means double the original pizel size etc. Leave for example levels > 2 > > and 4 unchecked. However, level 2 means 25% extra disk space but level 4 > > only 6.25%. Thus it may not make sense to skip other levels than 2. > Remember > > to compress also the overviews and test with external overviews which you > > can easily delete and continue with new tests. Internal overviews can be > > removed so that they are no more used but operation does not make image > > files smaller. > > > > > > > > > > > > ------------------------------ > > > > _______________________________________________ > > Qgis-user mailing list > > [email protected] > > http://lists.osgeo.org/mailman/listinfo/qgis-user > > > > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user >
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