Am 12.07.2012 12:25, schrieb [email protected]: > Message: 7 > Date: Thu, 12 Jul 2012 12:11:53 +0200 > From: Tim Sutton <[email protected]> > To: Bernhard Str?bl <[email protected]> > Cc: [email protected] > Subject: Re: [Qgis-user] Which android tablet > Message-ID: > <CALCNqkakHUNK3DWc2=MpjpTWDGOZ=b84gwevpsqh_83ntq5...@mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > Hi > > On Thu, Jul 12, 2012 at 12:01 PM, Bernhard Str?bl > <[email protected]> wrote: >> >> Am 12.07.2012 11:48, schrieb [email protected]: >> >>> Hi, >>> >>> has anyone tested the performance of qgis on android. >>> >>> I want to collect and store the position of 50 trouts tagged with radio >>> transmitters directly in the field. >>> >>> >>> What I did so far: >>> I have to aim at the targets from different locations at the river bank. >>> What I do now is simply draw lines on printed orthophotos. The fish is >>> located where the lines intersect. It is always quite a mess to >>> determine your own position. I could save the origin with a gps-device >>> but this takes too much time, would include "postprocessing" and adding >>> another step will increase the source of error. >>> >>> ... and it is not possible to walk into the stream ... >>> >>> >>> I am thinking of using a tablet, locally store the orthophotos (5 to 8 >>> pieces, format: .jp2, each around 130 MB) and save the points (e.g. >>> postgis). All metadata could be entered at once. No paper work. I know >>> where I am and can easily store, edit,.. fish data in the field. >>> >>> But I am bit worried about the performance. I takes about two til four >>> minutes to load those raster-layers at my desktop (Ubuntu 12.04, 16GB >>> Ram, QuadCore,...). The performance appears very poor. >> >> This is weird. I am not a specialist with raster formats but one of my >> aerial photos (geotif) 281 MB loads and displays within seconds, this is >> with pyramids (maybe you need to build these?) >> I even put some 50 of these photos into a GDAL virtual raster (VRT), it >> takes some 20 seconds to load but displays almost immediately. >> My machine is similar to yours hardwarewise (less RAM, though) running >> OpenSUSE 64 bit. >> > I think the jp2 drivers are quite slow. A nice solution is to load > your rasters into an mbtiles sqlite database - its not the best for > size, but its very good for performance. > > Note it needs a recent (unreleased?) version of GDAL.. Otherwise > convert your data to tiffs as Bernhard has done and optimise them for > performace by e.g. creating pyramids. > > Regards
Hi Tim and Bernhard, thanks a lot. the displaying performance highly increased after converting the raster set to geotif. Regards, Jens _______________________________________________ Qgis-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-user
